The 6.5 Grendel Forum :: For the Tier One AR Cartridge - Deconstructionism and the art of small arms design

Spartiate

Sorry for the frou-frou, artsy title. I don't really consider a man's thoughts reducible to the sum total of his environmental influences; however, as applied to inanimate industrial products such as firearms, the theory is a useful tool for critical analysis. Why is this necessary or important? Two reasons:

1. Most, if not all, mechanical means of utilizing the energy of powder deflagration to cycle a weapon automatically have already been developed. If there's another idea out there (I believe I might have hit on something myself; more to follow when I've worked out the details), it will be an amalgamation of existing principles. I don't believe I'm putting myself all that far out on a limb by saying this--like the guy who suggested closing the Patent Office around the turn of the century because "everything worthwhile had already been invented"--because:
A. I'm not predicting the impending culmination of an age of inventiveness, but recognizing that event as a historical fact fifty years after the last truly-original basic firearm actions were patented, and,
B. There are only a certain number of basic machines (lever, inclined plane, etc) and a finite number of combinations derivative thereof.

2. Most, if not all, of the existing concepts have been suboptimally implemented in actual firearm designs. Even many of the weapons regarded as close to perfection in functionality incorporate vestigial or otherwise superfluous features that unduly complicate manufacture, increasing their cost and creating a possibility of shortages or quality shortcuts in wartime production. Why? More to follow in the next post, regarding the history of small arms development.

The purpose I envision for this thread is to twofold; first, to dissect existing firearms (or common features of firearms) in terms of the respective historical context of each, asking the "Who-what-where-why-when"s as the first step in determining how future designs can be made better. Second, it is important for a designer to apply the same process to himself, to assess his own capabilities, limitations, and ultimate goals prior to assembling his drafting tools or firing up the CAD. I am confident, from reading past posts, that I have found the right forum and the right people to advance the art and science of firearms design.

Enjoy,
Mike

Spartiate

No dates of battles or names of kings to remember here--just historiography on the conceptual level. It really isn't even important to define when "modern" small-arms development began (I'd choose the introduction of viable self-contained metallic cartridges around the time of the Civil War, myself). It is necessary for our purposes simply to recognize cyclic trends and their effects on weapon development.

History can, for this purpose, be divided into periods of war and peace. The phrase "peace dividend" summarizes all we need to know about the latter: war-weary governments and populations wish to redirect the general revenue elsewhere. Whether a nation's thoughts and resources turn toward social spending, tax reduction, etc. doesn't really matter as regards weapons development; it suffices to say that during these periods the attitude of society reflects a general indifference, if not outright hostility, toward war, warriors, and weapons.

War is more complicated, but its essential characteristic (in the narrow context of our analysis) is desperation. There is a great deal of inventive dilettantism by REMF generals, raw recruits, and opportunists of every stripe. A genius or two will generally emerge from an educated populace, but the thrill of finally finding something that works from among the chaff often results in hasty deployment of the products of genius. Industry is often unable to perfect good weapons under wartime conditions, and unwilling thereafter. As the cycle continues, other worthwhile concepts are completely forgotten due to lingering memories of their employment in poorly-executed weapons.

Of course, not every nation fights even in "world" wars, and during times of "peace" there are numerous military operations. These transitional periods are important as well; indeed, the present (Global War on Terror) situation probably reflects a best-case scenario as regards weapons development: a national consciousness, but not a national economy, on a war/emergency footing--the sort of desparation impelling patriots and profiteers alike to churn out the proliferation of gear, weapons accessories, and new firearm designs in the last few years, as mentioned in numerous posts on this site, but without rationing, drafting all the factory workers, etc. Of course, the Cold War was an even better example in terms of, say, rocketry and submarines, but the widespread notion that nuclear war had made infantry combat obsolete rendered the era less prolific than it could have been, in terms of firearms development.

Time for work--more to follow later.
Mike

Coolhand77

I look forward to the contiuation of this thread. As someone interested in firearms design, and in the process of designing one myself, I have run into the same conclusion that whatever comes next, is going to be a variation of a combination of existing mechanisms and themes.

And yah, you hit the right forum :D

Spartiate

I appreciate your post. I'm sure I'll benefit from your knowledge and ideas on this thread, and hope to provide any help I can in return.

Thanks,
Mike

Spartiate

Since successful weapons design must begin as a capabilities-based process (the alternative, "What if I could build an automatic version of X?", approach having led to most of history's oddities and engineering dead-ends), the first step in deconstructing an existing weapon must be a recognition of what the designer was trying to do in the first place. For example, some regard the BAR as the ideal LMG on the basis of its WWII and Korea service, but the weapon's initial introduction in WWI for the "walking fire" role, and John Browning's own comments, make it clear that he was actually striving toward the Mission-Essential Tasks that we'd assign today to an assault rifle. It's a 19-pound M16! Of course, the fundamental soundness of the action is such that it evolved into what many today regard as the ideal GPMG--but only because FN's engineers were able (and willing) to recognize and bridge the gaps between the respective requirements of two very different missions.

Mission is, therefore, the basic "why". Many more will surely follow when you examine the various components, but first it's important to address the whole gun in terms of the other basic questions (in no particular order). The questions of "who" and "where" regard the designer and his national context--both the constraints and restraints imposed upon the designer by his government, his position in society (tinkerer, gunsmith, small-business/big business developer or engineer, ordnance bureau insider), and his cultural influences as well. Every time I examine the muzzle assembly of the MG-42 (whose combination of conceptual near-perfection, and considerable room for improvement in execution, largely inspired this thread), I am reminded of the scene in "Battle of the Bulge" where the field commander dismisses the staff general's faith in wonder weapons with a comment along the lines of, "I see the Germans are still the world's best toymakers!" The gun, "optimized" for manufacturing simplicity to the extent possible in its time and place, has a muzzle device that probably involves as many machining steps as a Garand's receiver!

The question of "when" regards historical context--where its development and introduction fell along the war-peace spectrum described earlier, what historical paradigms and prejudices informed its development (like the Civil War-era musket furniture--that dent-, splinter-, and warping-prone, heavy, disruptive-harmonic-inducing, clumsy and expensive collection of sticks, hoops, keepers, springs, screws, ad nauseam strapped onto barrels of rifles designed up through the fifties), and to what degree it has evolved since. While I am hardly a die-hard AR fan, I must admit that it is one of the few rifles that has continued to evolve over its entire service life (but especially in the last decade or so). Of course, it's ironic that some of the most recent "evolutions" of the AR, reflecting what many regard as its ideal form, have actually "regressed" chronologically to a piston design, retaining only the ergonomics and externals of the newer rifle.

"What" addresses materials science, and areas for improvement through the substitution of modern metals and composites. Again, to pick on the MG-42, it was a wartime emergency project by a nation strapped for raw materials and cash--subsequently adopted in peacetime by a number of war-weary nations not terribly interested in state-of-the-art small arms R&D--that could easily shed a great deal of weight simply through the substitution of thinner sheets of high-quality alloys for its mild-steel receiver, much less composites.

"How" is probably the deepest question; it ties in with the "component whys" mentioned above, and requires the highest degree of subjective judgment on the part of the assessor-designer. How a weapon works should be fairly obvious to a mechanically-inclined individual following disassembly of a weapon and/or study of manuals, diagrams, reference works, etc. On that note, I highly recommend Col. Chinn's The Machine Gun , particularly Volume IV, Parts X (physics of various action categories) and XI (exploded diagrams and descriptions of specific mechanisms). How to take what works, and leave behind what doesn't (like Michelangelo and his marble) is the challenge. Here is where you can take advantage of a sound concept that was poorly implemented the first time around, or modernize a design that was successful in its time, but later rejected because it was too heavy, difficult to manufacture, etc. (but perhaps not inherently so). Personally, I regard minimally/locally-stressed receiver designs, and further identification and minimalization/elimination of receiver stresses in order to create lighter and simpler weapons, as the most fertile ground for future developments, but there are probably as many ideas as there are inventors. Please share the wealth.

Until next time,
Mike

Essayons

An interesting topic for an interesting board, Spartiate.

It reminds me of something I've been thinking about a lot lately: the application of modern formal product management and requirements engineering techniques to small-arms development.

From what I've read, most of the small arms developed to date have been designed by inventive individuals or teams based on assumed or informally defined and prioritized requirements and then subsequently "tweaked" to work better for the user or role.

Basically, I think small arms development is similar to software development in that both are still often carried on as crafts. If that's the case, then small arms development, like software development, could benefit from a more formal, disciplined development approach.

IMO there is still ample room for improvement and innovation within the current small arms paradigm (metallic cartridges containing smokeless powder launching bullets out of a rifled barrel) IF we started with a clean piece of paper and used best practices to identify product requirements and engineer solutions for them.

A good place to start would involve putting people trained in requirements elicitation and definition best practices in the field with military personnel (or training selected military personnel in those practices) to identify their requirements. Ideally, we would do this without any preconceptions as to the solutions - e.g., without preconceptions about what type or category of small arm would fulfill the requirement, because the ideal solution might not be a SMG, PDW, AR, LMG, GPMG or other existing weapon or category. The best solution(s) might be new.

After we identify the users' problems or requirements, we need to prioritize their relative importance to the user. IMO failure to properly prioritize requirements was the reason the Lightweight Rifle, SPIW and OICW projects failed. (IIRC the OICW project did have a Product Manager and may have used good product management and requirements engineering practices, but the weight requirements was still obviously and grossly unrealistic givent the current state of materials science).

After we prioritize the users' rewirements, we can finally work on solving them. Ideally, I'd like to see this take place in a competitive environment with lots of engineering teams offering their best solutions to the users' problems and requirements. Unfortunately, there is not a huge market for new small arms designs, and not many entrepreneurs or companies would want to foot the bill for developing a weapon that might not be selected. We'd probably have to do what they do with fighter planes and pay several companies to develop candidates and then downselect based on competitive trials. (As you and I agreed in another thread, that path is often faught with politics and corruption - the best man does NOT always win).

Blah blah blah. Theres my $0.02 FWIW.

Coolhand77

Just to add in my two cents, I figure I should throw in my thought processes in designing my current project (of which I threw up some concept sketches on the Ideal Assault Rifle thread).
First I took the title and list of requirements that Grendelizer posted at the beginning of the thread.

An assault rifle should be:

1. Modular. Interchangeable buttstocks, pistol grips, trigger groups, mag wells, bolts and barrels, and optics.

2. Reliable. To me that says gas-piston, not direct gas impingement.

3. Ergonomic. Controls should be ambidextrous, not only for left-handers, but for righties shooting from cover on the weak side. This means the charging handle, the safety/selector, the bolt catch/release, and the magazine release. The firing controls should all be operated by the trigger finger; I think thumb operated ones are slightly more clumsy, but I wouldn't die if I had to have one.

4. Optics. A modular rail, picatinny or other, that allows for quick optics swapping with returns to zero is needed for short- and long-range scopes, backup iron sights, night vision, and laser spots and illuminators.

5. Buttstock, pistol grip, forestock grip: All should be interchangeable to mission, body fit, and personal taste.

6. Right side eject, for convenience of majority of righthanders firing mostly from the right shoulder.

7. Charging handle should be able to be used as bolt closing device.

8. Easy to field strip and reassemble.

9. Economic to mass produce in full-scale war-time.

10. Chambered in the 6.5 Grendel for use from point-blank to 1000 yards
And then I applied my own thoughts to it.

1. Modular. Interchangeable buttstocks, pistol grips, trigger groups, mag wells, bolts and barrels, and optics.
Personal preferences aside, the current ergonomic favorite seems to be the AR15 family. This can be seen with the adjustment of the FN SCAR project. Initially they had a grip and trigger guard on the L version reminicient of the SAW or the FAL. The current incarnation almost 100% mimics the AR15/M16 control placement. As a result, I decided to make the base trigger and grip arrangement similar enough to the AR15 as to have identical muscle memory for the various tasks while adapting some of the improvements seen in the XCR and SCAR weapons to the design.
2. Reliable. To me that says gas-piston, not direct gas impingement.
I totally agree with John here. Untill someone shows me another type of action that is as reliable, and will accept polymer cases (there are some new trends in that direction and fluted chambers WILL NOT WORK.) I'm going to stick with a short stroke piston or tappet gas operated system.
3. Ergonomic. Controls should be ambidextrous, not only for left-handers, but for righties shooting from cover on the weak side. This means the charging handle, the safety/selector, the bolt catch/release, and the magazine release. The firing controls should all be operated by the trigger finger; I think thumb operated ones are slightly more clumsy, but I wouldn't die if I had to have one.
Again an almost total agreement. My only caviat is to stick with the AR ergonomics as much as possible due to the obvious desire to do so from the actual operators in the field. That is one of the reasons I decided on an FN P90 style layout with top feed and bottom eject. It doesn't add any complicated mechanisms to the rifle (like the F2000's forward eject tube) that can jam up. To quote one of my favorite fictional charaters "The more complicated you make the plumming, the easier it is to stop up the drain."
I do however love the P90/F2000 saftey arangement and might just make the "trigger group" modular enough to switch between AR thumb lever and FN below trigger switch.
4. Optics. A modular rail, picatinny or other, that allows for quick optics swapping with returns to zero is needed for short- and long-range scopes, backup iron sights, night vision, and laser spots and illuminators.
Nuff said there.
5. Buttstock, pistol grip, forestock grip: All should be interchangeable to mission, body fit, and personal taste.
I would add that the standard unit should be adjustable to the individual soldier like the SOPMOD M14 stock or some of the Voltor stocks I have seen.
6. Right side eject, for convenience of majority of righthanders firing mostly from the right shoulder.
I dissagree only because I see the P90 arangement being so much more benificial, since your brass catchers hang off the bottom of the gun and not to the side, and spent brass doesn't get flung out to bounce around in CQB.
7. Charging handle should be able to be used as bolt closing device.
I concur, with the caviat that it be non reciprocating. Just add a locking mechanism to the handle so that in normal conditions it stays where it is during firing but if it is needed for a forward assist/bolt closing device, it can be engaged at a moment's notice.
8. Easy to field strip and reassemble.
Well duh. Must have there...especially after doing a strip down of a Remington Model 11 shotgun...yikes.
9. Economic to mass produce in full-scale war-time.
I agree here too. Thats why the base design is mostly sheet metal and polymer except for the high stress parts like the bolt, etc. Certain parts could be made either of low stress metals, polymers, or carbon fiber composits depending on cost, reliability, and strength issues. And of course any mounting points, or internal rails for components that slide back and forth would be manufactured from the appropriate materials. You just mould them into the plastic like they do with the P90 or most modern handguns.
10. Chambered in the 6.5 Grendel for use from point-blank to 1000 yards
No argument here. Just one addendum. Your base line cartridge should be the Grendel. but I would also propose that it be designed to be chambered for a variaety of different cartridges including .50 Beowulf, and anything else that will fit in an AR. After all, the 6.5 G is a great general purpose cartridge. The .50 Beo would be good for application in CQB and road block situations where a .50 BMG or other heavy weapon might not be appropriate but you need a bit more oomph. Not to mention the "cannister" possibilites with the beo.

Oh, and if the geniva convention is an issue because of the .50 cal clause, just use grendel case flared out so its a straight wall and start mouting .44 cal slugs in it. I don't think there is going to be THAT much of a drop in energy.

Anyway, thats my dollar (damn inflation)

Edit:
Oops, heres the other 50 cents I forgot.
Since ARs are being used in just about every environ, including as a PDW, design the system with the smallest envelope possible (my design can go as short as the P90, and only a little taller overall) and then make sure you can maximise your barrel lengths while keeping it within the current size envelope (with a 16 inch barrel and the stock fully deployed it is still smaller than a standard M4 with 14 inch barrel and the stock collapsed). Also give it the capability of being used in a SAW/Automatic Rifle role by allowing either drum feed or belt feed (still working on that...either going to be an MG13/15/34 style saddle drum, or a belt feed module to either fit in the magazine slot or replace the standard upper). Of course the barrel would have to be either a heavier fluted design or something else that sheds heat (can you say ABS), and quick change, just in case, but those are easy to incorporate with todays design techniques and still retain accuracy.

Spartiate

Essayons,
Thank you very much. It seems as though we are on the same page regarding the need for a formal process of requirements-based firearm development, and also agree on some important particulars as regards execution. I also agree completely that ". . . small arms development is similar to software development in that both are still often carried on as crafts"; however, I believe looking at looking at firearms design from a software industry perspective must take into account some fairly substantial differences, namely:

-Software design is an advanced science in a continual state of growth and flux, some would say at an exponential rate. Gun design involves the interplay of simple, tangible mechanical principles within the grasp of anyone with rudimentary mechanical skills. Nearly every gun mechanism imaginable was conceptualized, and many were built, by the 1880s; all were constructed, most in fairly advanced form, by the 1950s. Since then we've only been perfecting and accessorizing (or, in some cases, forgetting and stagnating; hence this thread).

-Software firms, of all areas of the private sector, probably best epitomize the differences between free enterprise and the monolithic, inertial, suffocating federal bureaucracy. A good idea for a new, let's say, video game or IM program would (I imagine) be staffed bottom-up by relatively driven, imaginative, competitive go-getters who would, at each level, understand the connection between new ideas, job security, and promotion, and would--we hope--convince a corporate headquarters aware (if it's a successful company) of the importance of competing for every bit of market share, in every area of the company's interest, in order to profit and succeed. If one wished to pitch a new rifle design, on the other hand, the process would have to begin at the top (with far smaller chances of initial buy-in), be driven top-down (by a "corporation" fully aware that project failure would not perceptibly affect the outcome of the GWOT) and staffed by career procurement officials only remotely connected to those whose fortunes would rise and fall with the project's. This is where your idea, "A good place to start would involve putting people trained in requirements elicitation and definition best practices in the field with military personnel (or training selected military personnel in those practices) to identify their requirements." is very much a necessity. I'm currently one of the military advisors (in an extremely small role) to a consortium of contractors who are designing a new class of warship. It is clear from some of the team's comments that this is the first time operator advisors have been brought in, at least to this particular area, and that while they are quite open to, and indeed solicitous of, our feedback as to how to execute mission specifics within their overall plan, they are not terribly interested in common-sense observations calling into question preconceived notions on the conceptual level, which have long since been written into the contract.

-"Computer Software" is an enormous field of endeavor more analogous in scope to "Military Hardware" than to small-arms. That may sound over-obvious and patronizing, but the key point I'm getting at with all three observations is that computer software development is a huge field of play with infinite possibilities, whereas small arms design consists solely in tweaking a small handful of existing products. We're already at about a 90% solution (and have been in the eighties since the fifties, so to speak); some substantial and legitimate individual gripes notwithstanding, the present situation isn't irreparably broken. We're basically just looking for the M-16's ergonomics, field-stripping simplicity, and full-auto characteristics (controllability and lightweight ammunition) with 7.62 reach and stopping power (which is why we're on the Grendel board :D ); improvements in ruggedness and reliability are also required. Compactness for portability in vehicles and maneuverability in MOUT is high in many wish lists, as is modularity (to varying degrees, from Picatinny rails to belt feed modules), but it's all out there and needs only to be properly packaged--an evolutionary vice a revolutionary process, IMHO.

You also wrote,
Unfortunately, there is not a huge market for new small arms designs, and not many entrepreneurs or companies would want to foot the bill for developing a weapon that might not be selected. We'd probably have to do what they do with fighter planes and pay several companies to develop candidates and then downselect based on competitive trials.
Again, I must respectfully disagree, in that there are probably a hundred innovative private companies (several of which are represented in this forum) constantly developing aftermarket components and accessories for our primary service rifle alone, not to mention a dozen others hungrily developing and marketing competing designs. Fighter aircraft (and ship, and numerous other) big-ticket item R&D is a necessary evil ("necessary" due to the otherwise-unbearable expense of development and prototyping; "evil" in virtually every other respect--the corruption you yourself mentioned, a horrible failure rate, with price tags routinely surpassing the GNPs of many developing countries, etc. etc.).

Thanks again, and keep the ideas coming,
Mike

Spartiate

Coolhand,
Are you 32, 5'10", blue-eyed . . . because after rereading John's ten requirements (with which I agree 90%) and seeing that your minor differences with the original precepts largely reflect my own to such a great degree, I think we might be brothers. I do have a few minor questions/counterpoints, though, which I hope you might be able to answer:

On #2: What are the advantages of short-stroke over long-stroke gas piston operation? Personally I'm a recoil fan (among other reasons, for the lack of additional parts/subassemblies required), but at least until/unless I develop and perfect a viable design, competitive in the listed categories with existing systems, I'm willing to concede that everyone seems to want gas operation. I've always favored long-stroke because it minimizes additional parts and complexities (the AK, for instance, with its tubular bolt carrier and compression spring in the same place I'd put an extension spring). On my FAL and SKS, by contrast, it's always seemed superfluous to complicate matters (added length in the SKS; that #$%^& angled tube on the FAL, which confounded my early attempts to produce a nice wooden buttstock) when simply strengthening a spring and threading the piston end into the carrier face would be so much easier. What do you gain?

On #3: I agree with your first point regarding the safety (although I can't really disagree with the second, having never used a P90). For all its other foibles, the AR's safety manipulation is like the .45's (universally beloved by speed shooters), only better (because its grip doesn't need to accommodate a magazine).

On #6: I agree with your preference for a bottom-ejecting bullpup, to the extent that it could be made the equal of existing designs when it comes to feed-reliability. Again, I cannot debate your point effectively because I have zero experience with the P90, but I must confess a degree of skepticism regarding its magazine gymnastics. I am quite conservative when it comes to reliability, and inclined to default to convention in the absence of substantial proof of a new design's functionality under combat conditions.

On #7: I'm inclined to disagree here. I've always found non-reciprocating cocking handles somewhat of a superfluous affectation, unless absolutely necessary as in a pistonless design like the AR. I have an instinctive dislike of extra parts in general and of tiny pins, springs, and clips in particular. Any sort of non-recip handle will need a set, and a non-recip doing double duty as you propose will most likely require another (like the Izzy FAL). If you use a poly receiver, the retainer clip also chews on plastic. I think an (integral) operating handle belongs at the juncture of the piston and recoil spring tube (on an AK setup), or even further forward (if a female piston is used) where it will be well clear of the shooter's face, yet bear fully on the moving parts themselves rather than interfacing with piston or carrier solely through a spring-loaded nib.

On #8: Full agreement, but with a further stipulation: "Easy" for me does not involve punching pins like the AR's--which, if tight, are a pain in the ass, if loose, allow play between upper and lower, and in either case cannot be accomplished with the fingers alone. I'd much prefer a lever as in the FAL, or even better (no extra parts!) a tab on the rear of the recoil assembly as on the AK.

On #10: Agree, but more so with another poster on a different thread (don't remember specifics either way) that a straight-wall Grendel (.40 or .44?) would be preferable to the current Beowulf for this purpose due to magazine capacity. Something I'd like even better for CQB (since for my troops it takes place inside high-yield-steel ship compartments--during intruder scenarios and boarding operations--rather than more ricochet-forgiving wood, plaster, or concrete buildings) would be a bullpup shotgun, an idea that occurred to me when colleagues involved in security training pointed out the difficulties inherent in teaching weapons retention with the issue Mossberg 500 and Remington 870. I'm putting the finishing touches on an Ithaca 37 for home defense, but something with ergonomics similar to the standard service rifle would be infinitely preferable for military use. The similarities between the Saiga 12 and the stock AK have me thinking that that's not too far outside the realm of possibilities.

I agree with your final point about the need for a SAW using the same platform, with the sole caveat being (assuming a bullpup) that you are able to clear the shooter's face and arm. I'm interested in seeing your solutions.

Take care,
Mike

Essayons

Essayons,
however, I believe looking at looking at firearms design from a software industry perspective must take into account some fairly substantial differences

Agreed. Firearms development is way narrower and more mature than "software development." My experience is in tax compliance software. The requirements seem obvious if you focus on tax laws, regulations, publications, instructions and forms, but get WAY more complex when you start to look at how people use (or want to use) it in their businesses. Similarly, some small-arms requirements are obvious, but there are probably many many more important requirements that aren't.

I also agree that a new rifle design would have to be driven top-down and would be subject to the limitations and risks you mention.

Finally, I hope my assertion that there is not a huge market for new small arms designs, and not many entrepreneurs or companies would want to foot the bill for developing a weapon that might not be selected is wrong.

HK, FN, Robarms and others (e.g. China's 5.8x42 family of weapons and the Russian AN94 Abakan) are doing some original things. As you point out, there are also whole industries selling AR, AK and FAL based firearms, parts and accessories. For example MGI's QCB upper and modular lower with interchangeable mag wells.

I'd just love to see what the US small arms industry and military could do if they started with a clean piece of paper and used best practices. I hope the result would be more impressive than the XM-8, with which I am thoroughly underwhelmed. Why replace one 40 or 50-year-old design with another (the AR16 via the AR18 and G36)? Especially when many, if not most, of the XM-8s claimed advantages over the M16 were related to the cold-hammer forged barrel (available on Diemaco/Colt Canada's M16s).

If you haven't taken a look at Solidpoint's design, it's worth wading through the other thread to find it. Picture a Garand action flipped upside down with a top-feed system (solidpoint's got some interesting ideas there) and you get a rough idea.

Coolhand77

Coolhand,
Are you 32, 5'10", blue-eyed . . . because after rereading John's ten requirements (with which I agree 90%) and seeing that your minor differences with the original precepts largely reflect my own to such a great degree, I think we might be brothers.
Hehe, sorry to dissapoint, but I am 6 ft, 29, and green eyed.
On #2: What are the advantages of short-stroke over long-stroke gas piston operation? Personally I'm a recoil fan
There is some confusion between short and long stroke pistons.
From en.wikipedia.org/wiki/Gas-Operated
A long-stroke gas system is generally defined as one which the stroke of the piston under pressure is greater than its diameter. Because of the greater dwell time, gas must be ported from the barrel very near the muzzle of the weapon as in the M1 Garand. This relatively lower pressure gas acts over a longer period of time to impart the same amount of energy to the operating system. Because the operating parts are longer, they are necessarily heavier and this system is not used in modern weapons.
A short-stroke gas system is defined as one which utilizes high pressure gas from the middle portion of the barrel that impinges on the piston head for a short period of time before excess gas is either cut-off (M-14) or vented (AK-47) or the piston head reaches a stop (M1 Carbine). The distance the piston travels under pressure is generally less than its diameter. The piston may or may not be attached to the bolt carrier. This is the most common type of gas operation.
A gas trap system is similar to long-stroke operation, however gas is 'trapped' after leaving the muzzle. The "Bang" rifle and early "gas trap Garand" rifles use this system. The German MG-42 machinegun and other recoil operated weapons use this energy in combination with recoil energy for more reliable and energetic operation of the weapon. The gas trap system is also obsolete.

The direct impingement method of operation vents gas through a tube to the working parts of a rifle where they directly impinge on either the bolt itself as in the M16 or the bolt carrier proper.
Notes on Operation:
The terms 'short-stroke' and 'long-stroke' are often confused by both laymen and experts. The 'stroke' is that portion of time when combustion gasses contact the piston head prior to venting. It is not the total length the piston head might travel during the cycling of the action. The commonly reported misconception is that a piston being rigidly affixed to the bolt carrier is what constitutes a long-stroke system. In fact, the 'stroke' is virtually the same for both the mislabeled 'long-stroke' AK-47 and correctly labeled short-stroke AR-18; the gas port is in nearly the same location along the barrel. The description of the AK-47 and others with pistons attached to bolt carriers as being of long-stroke operation is erroneous.
I personally would perfer recoil too, but there are issues when using a full power load, or an "intermediate" power cartridge like the Grendel that would make the recoil buffering too long for a bullpup rifle unnessicarily increase the weight over a gas operated system.
On point 3: think of it like the AUG saftey only it is operated by the trigger finger instead of manipulated by the weak hand as a crossbolt.
On #6: The P90 magazine has proven itself somewhat stable. The early reports of the ammo "jumbling" in a dropped partial are exagerated and do not happen anymore. Pick up the Feb 6 2006 copy of Shotgun news for a review of the civilian model. Needless to say, to keep the width narrower, instead of turning the cartridge 90 degrees to the bore, a lighter turn is theoretically possible. My design is about a 60 degree to allow for 30 rds in the magazine.
On #7: The only reason I perfer the non recip is because that way you have no external parts moving back and forth during fireing to possibly catch on something in an akward moment and either jam the gun or hurt the operator. Also, the idea I have for the locking handle is not "spring loaded" or flimsy. Its a positive locking knob. and the "slider" would fit in a metal rail moulded into a plastic reciver.
On #8: I agree, the pins I had in mind were more like the ones on an HK91 style rifle, though levers and clips are much more paletable. I'm still working on the design though so I may as yet find a way to work it the way I want.
On #10: I totally agree with the sentiment about the sagia. In fact my thought process involved a "shotgun style" smooth bore semiauto/full auto to minimize ricochet and blow through.

as for the feed on the SAW, the dual saddle drum would be in front of the gunner, not only below his sight line, but also help protect his face from incoming fire. IN a belt feed it would also be in front of his face for monitering, but the links would go out the left side and the empties would go down. Not only that, but the chutes for feed and link disposal could be on the sides of the gun and turn 90 into the receiver.

I personally like the saddle drum idea better...keeps the gun lighter and simpler, but belt feed would allow for linking multiple belts together for sustained fire.

Spartiate

I hope the historiographical process I described earlier is a useful tool for analyzing existing firearms in context. For future firearms designs, I believe it's necessary for the developer to take a hard look at his own situation in like fashion.

"Who", as with historical designers, refers to your position relative to the gun-design world, and largely concerns your material situation. Are you corporate or military R&D, an engineer or machinist with a generally non-gun-related firm, a gunsmith with an established small business, or (like me) a tinkerer with a tool stuffed into every crevice of a narrow basement? Who do you know (or have been in contact with), and what are your prospects for securing investor backing, military or LE trials, or a license to manufacture? What outside resources can you use to circumvent the shortfalls in your own tools and facilities? I've never actually utilized their services, but http://www.emachineshop.com/ (E-Machineshop) advertises most mechanical forming processes as well as heat treatment and even finishing; they might be worth checking out for individual components (although I wouldn't recommend pushing your luck with either the company or the Feds by trying to commission a receiver, FA conversion parts, etc.) How can you leverage some of your weaknesses into strengths? I believe, for example, that my need (as a private experimenter) to rely on commercial metal forms for basic parts can be an advantage for later industrial production as well, eliminating the need for superfluous machining steps.

"Where" is mostly a legal question, as it regards the firearms (and possibly small business) laws in your area. If you live in a socialist foreign police state (like parts of Europe, or California), you'll probably have to secure government backing from the start, take a partner who lives in an area with more latitude for experimentation, or move.

"When" addresses your personal timetable for development, experimentation, testing, and submission to potential manufacturers and/or customers (possibly also backers or partners), which should also take into account the pace of development (I'm sure we've all let some of our good ideas remain good ideas, while others with similar thoughts went out and drew, built, and marketed theirs first) and the timing of mil/LE trials, design solicitations, etc.

"What" and "How" are closely related, and get into the meat and potatoes of the capabilities-based design process. "What", in this sense, regards mission requirements--(Grendelizer's 10-point "Ideal Assault Rifle" manifesto, and Coolhand's commentary thereon, provide a good foundation for such an assessment). "How" addresses execution of your design in terms of general principles/preferences as regards gun design, guiding the synthesis and packaging of desirable features to meet your specifications. Examples abound, particularly the various approaches to improving the AR-15 platform, where the backgrounds of the respective designers (competition shooter, varminter, LE sniper, SOF, etc.) are often evident.

Take care,
Mike

Spartiate

I'd just love to see what the US small arms industry and military could do if they started with a clean piece of paper and used best practices. I hope the result would be more impressive than the XM-8, with which I am thoroughly underwhelmed. Why replace one 40 or 50-year-old design with another (the AR16 via the AR18 and G36)? Especially when many, if not most, of the XM-8s claimed advantages over the M16 were related to the cold-hammer forged barrel (available on Diemaco/Colt Canada's M16s).

If you haven't taken a look at Solidpoint's design, it's worth wading through the other thread to find it. Picture a Garand action flipped upside down with a top-feed system (solidpoint's got some interesting ideas there) and you get a rough idea.

I couldn't agree more regarding XM-8 as the mascot of an old procurement bureaucracy crying out for help. In the Navy we make old COTS technology "better" by boxing it in huge gray cabinets with lots of screws. In current small-arms design the current trend often seems to boil down to repackaging old rifles in space-agey (as envisioned by Art Deco-era comic illustrators) plastic (although the XM-8 pales in this regard beside some of the other oddities out there).

On which thread is Solidpoint's design? "Ideal Assault Rifles"? Come to think of it, where is SP himself? I would think this sort of discussion would be right up his alley, and applicable to PAV design as well.

Thanks,
Mike

Spartiate

There is some confusion between short and long stroke pistons..

Thanks for the edgimication as regards short/long-stroke pistons. I am, however, still in the dark as to why some designers do choose whatever you call what I originally described as "short stroke"--i.e. where the piston just slaps the carrier until it unlocks, rather than being integral. I understand it's necessary for retrofits of the AR (which doesn't have room in the upper for a tall/wide AK-type carrier), but it seems like undue weight and complexity in a ground-up design.

"I personally would perfer recoil too, but there are issues when using a full power load, or an "intermediate" power cartridge like the Grendel that would make the recoil buffering too long for a bullpup rifle unnessicarily increase the weight over a gas operated system."

I don't think there's anything intrinsic to a recoil action that requires extra buffering (a function of bolt velocity and desired ROF in an auto). Chinn's MG Vol IV lists the ease with which gas actions may be tuned (by adjusting gas bleed) as one of their primary advantages, and goes on to describe how early gas guns were designed to match the bolt-velocity parameters established as desirable in preceding recoil designs. I believe the primary challenges in recoil operated design are the need to accommodate a moving barrel, and provision for something outside the recoiling mass (as opposed to the bolt carrier as in a gas gun) to unlock the breech at the correct moment.

"On point 3: think of it like the AUG saftey only it is operated by the trigger finger instead of manipulated by the weak hand as a crossbolt."

I'm not familiar with the AUG safety, but I assume it's a crossbolt accessible to the trigger finger, like an MG-42's in reverse. That wouldn't be bad (although the more accessible you make it to the trigger finger, the more you increase the likelihood of inadvertent deactivation). I still think the AR's hard to beat.

"On #6: The P90 magazine has proven itself somewhat stable."

I'm sure you're aiming somewhat higher than "somewhat stable" ;) in your design?

"as for the feed on the SAW, the dual saddle drum would be in front of the gunner, not only below his sight line, but also help protect his face from incoming fire."

How is this possible in a bullpup design?

I generally incline toward conventional mags and belts due to the fact that I will probably have to have a design in some semblance of working order before I can even approach a manufacturer, backer, or customer, together with an acceptance of my limitations--it is not only beyond the capabilities of my workshop to fabricate something as complex as a saddle drum, but probably beyond my ability to even draft to the degree of precision required for reproduction by someone like E-Machineshop--particularly when I consider the cost vs. the rather high probability of failure with something that intricate on the first try or two (or seven). One unconventional idea that occurred to me the other day, though--which might fall in your area of interest--was something I like to think of as the "doughnut drum" (maybe I should post it on the "Doughnuts!" thread?). I was reading the "Ideal Assault Rifles" thread, where you guys were talking about angles of feed and ejection, when I followed TWL's link to the MGI site, and saw their drum magazines. I have one of the AR 90-rounders, but it was the 10/22 U-drum that got me thinking. If you flattened a drum to be more like that sort of unobtrusive shape (but scaled up for intermediate cartridges), used a spring-and-follower arrangement (like the 90 rounder) rather than the constant-force spring used for the .22 (which takes up space in the middle of the magazine), you might be able to tilt an action 90 degrees to feed from the left and eject down and back through a channel in the middle of the magazine.

Take care,
Mike

Coolhand77

Okay, I'm only guessing here, since I don't know the exact why, but I can postulate. The fixed piston requires a heavier bolt carrier to handle the stresses imparted on the junction of the rod on bolt carrier. Examples of course would be the AKM family and derivatives. If the operating rod is not perminantly attached to the bolt carrier, and has some "movement" to somewhat dampen the stresses between the two components, then you can lighten up the mechanism. An example would be the M14 or the Mini-14, and the g36/xm8.
As far as I know, they are both very reliable, and the only difference being, I think weight.

The only issues I see with delayed recoil operations is that the components are suceptible to dust and can be jammed by same, also due to the reduced energy for extraction/ejection, you need fluted chambers, which precludes the use of stuff like polymer cases. It also makes the bolts more complicated to manufacture.

By somewhat stable, I mean more reliable than older AR15 magazine designs or previous incarnations of the beta c magazines.

Speaking of the beta C mags, that is an inverted saddle drum with a magwell extension on it. Just take the "AR15" magazine extension off the beta C and invert it. Then you design the SAW upper so that the saddle drum rides were the feeding portion or the stick magazine (my design idea anyway) is normally, just in front of where the operators face is. IN fact I might just start the initial design with that since "chopping" the mag well extension off a beta mag is going to be quicker than designing the new mag and the SAW upper will be usable in a "Carbine" configuration like the new shorty M249s.

IN fact if I were to use that design as the common reciver, getting rid of the "feed magazine from either side" idea and going back to a P90 style top loading magazine. hmmm that has possibilities...a little slower than an AR reload, but adds better commonality to the system overall.

I'm not discounting your "donut" idea either.

Also, one of my later ideas was to rig an extension on the operating rod that would run a conveyor type system in a magazine. That would do away with the spring in the magazine and improve the magazine capacity. Thats a design for down the road though.

I'm enjoying this thread immensely, and its giving me new insights.

Essayons

Spartiate, here is a link: http://www.65grendel.com/forum/showthread.php?t=8&page=34&pp=10 (2/3 the way down)

I misattributed the design - it is Coolhand's.

I've been thinking along similar lines for a while. When I was a kid I "designed" a Mini-14 bullpup with a schematic and tracing paper. Later it occurred to me to turn it upside down and feed it with a helical magazine (a la the Calicos and Bizon SMG) that would double as the dust cover.

Helical mags have a lot of drawbacks - mainly the wasted space in the center - but I still like the idea of a large top-mounted mag as the dust cover (the kind of mag Coolhand has been talking about for a while now). Ideally "field stripping" would consist of removing the mag and then pulling our the breech-block/bolt and related parts. The mag would go between front and rear sights firmly attached to the barrel/lower receiver.

Would it be worth taking another look at Johnson's rotary mag or something like it? You could make it out of dent-resistant fiber reinforced composite (a la the Bizon IIRC) and would not have to worry about bent feed lips or the weight of mags with sturdy feed lips. Just shoot five or 10 and strip 5 or 10 in. Maybe you could combine Johnson's concept with a helical design wrapped around the barrel to form a hand guard. Then you could increase the capacity.

I still prefer standard mags for redundancy (you'r weapon would be out of action if an integral mag malfunctioned, but it worked in the Garand) and form factor (about as compact as you can make a quantity of cylindrical ammo).

Coolhand77

Grins...glad to see the design has stuck...I've actually progressed alot further on the design, even to the point of starting the CAD drawings. One thing I did change was the trigger/grip ergonomics. The current design is directly based off the measurements of the AR-15 so that it would be compatable with the current set of grips, as well as letting soldiers use thier AR15/M16 muscle memory.

Its funny that Essayons and I actually had the same inspiration.

I'm still working on some design criteria, such as possibility of using a double drum like an inverted Beta-C and going back to the P90 style magazine insertion method.

As any good designer, I am willing to listen to ideas and suggestions, so keep on thinkin

Spartiate

The only issues I see with delayed recoil operations is that the components are suceptible to dust and can be jammed by same, also due to the reduced energy for extraction/ejection, you need fluted chambers, which precludes the use of stuff like polymer cases. It also makes the bolts more complicated to manufacture.

For a man who clearly holds a PhD in gas operation :D , you have committed the one unforgivable sin :eek: of confounding recoil operation (barrel, locked to bolt, recoils for a certain distance before unlocking, generally transferring energy to the bolt before being brought to a stop) with delayed blowback (fixed barrel, no true lockup). Solidpoint and I discuss the critical differences here (http://www.65grendel.com/forum/showthread.php?t=448&page=7&pp=10) , but specifically with regards to the initial-extraction issue you raised--delayed blowback is a fine solution for using lighter bolts in SMGs than pure blowback allow, but unsuitable for high-pressure rifle cartridges without the use of such expedients as the fluted chambers you mentioned; recoil operation, by contrast, introduced the concept, and is successfully employed (rarely, if ever, with a $%^&* fluted chamber) for most handguns 9mm and above, the M2HB .50 caliber machine gun, up to and including most heavy artillery.

A pox on you :p
Mike

Coolhand77

Damn, do I feel like a rube :D

Backing up and rethinking my comments...the only issues I have heard about RECOIL operated (My only excuse was I was tired an distracted at the time I typed that :o ) is that with a barrel that moves there is an accuracy issue and variable strength loads will cause failures to feed/extract or damage due to springs that arn't strong enough or too strong (recoil operated shotguns). This could just be the prejudice of the gas op world, but I will research further.

Actually I am now going to have to research recoil operated firearms and see if I can't ditch the gas powered op rod. Its been one of the things that has made it difficult to shrink down the gun as far as I wanted initially.
One other things I was looking at was setting up the design to use an AR barrel with a tappet in place of the gas tube mount. That way existing manufacturing can be used to make at least ONE component. If I can use the same barrel with out the gas port (removing a step in the process) thats even better.

Spartiate

Now that I've got that out of my system ;)

Thanks for the link, Essayons. It helps me visualize the current discussion points raised by you and by Coolhand. I'm still trying to figure out the ergonomics of the proposed saddle drum, though. Without access to an actual rifle for confirmation (my gun cabinet is on the other side of my sleeping wife), when I bring my hands up to shooting position, my right thumb is just below and forward of my nose--which, for the design pictured (and bullpups in general) puts the mag parallel to my faceSA-80 (http://en.wikipedia.org/wiki/Image:British_soldier_with_L85_b.jpg) AUG (http://www.steyr-aug.com/jill_aug.jpg) --or, in the case of a saddle drum (it seems) in it. I like the idea of the weapon's cycling driving the mag (like the Lewis) if you can find a way to make it work.

I've always liked the helical idea, and agree that it has great potential for top-feed, bottom-eject bullpup employment (with the feed direction reversed, of course). A Grendel cartridge occupies about three times the volume of a 9mm, so you'd have to extend it all the way to the muzzle for good capacity, but even then the compact, centered load would make for a more portable package than either a dragging belt or an off-center belt box. I don't know if I'd make it the replacement for the whole dust cover, though, since (without the utmost caution) every mag change in the Sandbox would entail dumping a dune into the top of the works. A bit of sheetmetal between the majority of the works (except for the actual feed port) and the environment, IMHO, would go a long way in terms of cleanliness/reliability while adding little in the way of cost, weight, or complexity.

There's a lot to like about the basic Johnson action (and this is just the thread for discussion thereof), but I believe it was actually the mag (along with inadequate forward barrel support) that killed it. In any event, given what you said about wasted space in the middle of a helical mag, keep in mind that for "a helical design wrapped around the barrel to form a hand guard", that wasted space would have to include the barrel and sufficient spacing for cooling--and your hand would have to fit around the outside. I think the original Calico design would probably be a more practical starting point.

I started this response yesterday, then put it on hold for work; hopefully I can finish this time before leaving again. One more comment (or recoil-op commercial, depending on your point of view), as regards Coolhand's last post:
"the only issues I have heard about RECOIL operated (My only excuse was I was tired an distracted at the time I typed that ) is that with a barrel that moves there is an accuracy issue"

Provided the barrel is only permitted to move fore and aft, there is no effect on accuracy (the M2HB is by far our most accurate infantry weapon except for specialized sniper rifles, and has of course been used in this capacity itself), and even the tilt-to-unlock barrel on the 1911 hasn't hurt its reputation as the hands-down favorite of competitive combat pistol shooters (due to timing). I will grant you, though, the action generally lacks the adjustability of (some) gas-ops, although this hasn't proven to be a showstopper in either case (i.e. .50 cals or AK-47s) due to the standardization of military ammunition. There are certainly variations, but Grendel ammunition, for example, will never show a 3 1/2" Turkeymag/1-ounce dove load variation in recoil and pressure.

Duty calls,
Mike

Coolhand77

Spartiate

Yah, I agree. There is one problem that I have noticed though. You can't just barrel swap for change of configuration. Any decrese or increase of mass and you have to adjust the springs in the weapon. Otherwise you have a function issue. The M2 doesn't change barrel length or weight, nor do shotguns. My idea allows you to change the barrel and the tappet (all one unit, along with front sight and maybe forward upper like the p90...still working out details) but the spring pressure doesn't need to be changed. an example of this would be the M1 enforcer carbine. Regular length barrel or sawed off barrel, the carbine still functioned. Same with the FAL, Mini-14, etc. I'm not sure a recoil op can be modified without some spring swapping as well.

Agreed. Any gas system's cycling is completely independent of barrel weight, and an adjustable gas system will accommodate varying barrel lengths as well, to the extent permitted by its adjustment range. My FAL, with its 21" barrel shortened to 16.5", runs reliably with quality ammunition (at a much higher setting than that recommended for a normal length barrel, with an aftermarket piston), and won't fully extract cheap Indian surplus with any consistency at all. Of course, non-adjustable gas systems have even less flexibility in this regard; an AK barrel hacked off just forward of the gas chamber won't make a reliably-cycling Krinkov, and even the purpose-built short Krink action, IIRC, requires its muzzle device to build sufficient pressure for cycling. Of course, since you are designing your system with such flexibility inherent from the beginning, it should be comparatively simple--just make the gas port large enough, or locate it close enough to the breech (probably a better idea to permit PDW-size barrels), and provide enough venting or cutoff to attenuate the pressures generated by the longest barrel envisioned. The only possible drawback might be a training issue: the FAL manual directs the shooter to start at the weakest/most vented gas setting, shoot, adjust up one, shoot, etc. until it cycles reliably, then adjust up a click or two. If a shooter took a rifle with a broader adjustment range (designed to cycle anything down to a 12" barrel, let's say), in the configuration likely to produce the highest pressure (i.e. a 24" DMR barrel), and started with the gas on the highest setting, he'd pound the crap out of the gun. Robinson's website states that current military requirements dictate non-adjustable gas systems for this reason; their solution with the XCR was to use a system requiring tools to adjust. Of course, it might just be easier to ensure your barrels each have a gas port drilled to a diameter proportioned to function reliably and safely for that particular length.

Recoil is admittedly a greater challenge, especially when it comes to lightening a barrel without changing its length (like trying to make an "M2LB"). I wonder how much changing barrel length while maintaining a consistent contour would affect functionality, though. I was thinking about the problem of a lighter barrel while rereading your post, specifically in terms of how to increase locked recoil travel to compensate for the barrel's decreased mass/inertia, when it occurred to me that a barrel that was not only lighter but shorter would, all other factors being equal (in a gas-op gun, for example, where barrel weight would not be an issue) contain the bullet and expanding gases for a shorter period of time, have a shorter pressure curve, and consequently require a shorter dwell before unlocking. Would the two factors balance each other out in a barrel both lighter and shorter, resulting in reliable performance with the same locked-recoil stroke? I'm sure I could punch the numbers using the equations provided by Col. Chinn, but it's too early in the morning to do math.

On the other hand, to the extent necessary to adjust cycle timing for reliable functioning with various barrel weights, I have thought of a few methods. The closest parallel to matching gas port sizes would be matching barrel-extension geometries (since QCB, recoil or gas, generally dictates that barrel and extension be headspaced as a unit and changed together thereafter) to barrel lengths, to achieve the desired duration of locked travel (this would obviously involve a great deal of trial and error--probably with a small file--in the prototyping process). On the other hand, here's an idea more akin to the adjustable gas system: One of my basic design precepts is minimizing receiver stresses to allow for both lighter weight and lower recoil. In a recoil design, that means that the major stresses (particularly that borne by the component(s) arresting rearward barrel travel and deflecting the locking portions of the bolt out of their recesses in the extension) must be sprung rather than welded, riveted, screwed, or otherwise statically fastened to the receiver. A camming piece untethered from the receiver could be made adjustable without a great deal of difficulty, enabling the operator to control dwell timing and therefore bolt velocity in a manner similar to gas adjustment (albeit with the same potential drawbacks).

Keep up the great posts. I look forward to seeing more drawings as you incorporate the different features you've been describing.

Take care,
Mike

Coolhand77

Spartiate

One other issue with recoil op systems that I realized was that in the event of something contacting the barrel, you may have faliures to cycle. Case in point was the 1941 Johnson rifle and LMG. It worked fine, unless something contacted the barrel during cycle, or they hung a bayonett of the barrel.

I agree 100%, and alluded to that fact a few posts ago: "There's a lot to like about the basic Johnson action (and this is just the thread for discussion thereof), but I believe it was actually the mag (along with inadequate forward barrel support) that killed it." (emphasis added) Although it was mostly the MG-42, and to a lesser extent the AK-47, that inspired this thread, the Johnson is a veritable poster child for deconstruction-reconstruction, combining a fundamentally sound action (which inspired the AR's) with a plethora of "birth defects"--vestigial or quirky design features--that guaranteed its overall failure in competition against the Garand. There is no way I would ever leave over a foot of barrel sticking out the front (let alone hang a frickin' bayonet on it!). In a full-length design, this could be a design challenge at worst, extra tubing (and extra weight) at best; but in a bullpup, it hardly requires a second thought. Taking into account ergonomics and other factors (attachment point for sights and accessories), there has to be something out there on the front of the gun, and it may as well support the barrel. Right now I favor a forward barrel bearing threaded for a muzzle device (brake or suppressor, mission depending), supported by upper and lower Picatinny rails (one of which would contain the recoil spring, and gas tube if I went that route). I think quads are superfluous; there is only a certain number of accessories you can hang on a rifle (particularly a compact rifle), and offsetting one or two to clear each other can be accomplished with a great deal less weight and bulk than two whole extra rails.

You wrote:
"My principle design is set up to use a short op rod so that the minimum barrel length would be about 10 or 12 inches. With a tappet system (similar to the G36 and the XM8) the piston is fixed and impacts on the op rod only enough to unlock the barrel and allow the residual pressure and recoil to cycle the weapon. The excess gas pressuer gets bled out a port to avoid blowing your piston (with longer barrels) and the rod is optimized for short barrels."

I guess "tappet system" describes what I would have called, before my re-education, a "short-stroke gas system"--so you did go that route (I still don't quite grasp the benefits over an AK system, but little differences like that make the world go 'round--and make gun shows more intersting ;) ). I wonder if porting would fully address the differences in barrel length/gas pressure. If your orifice is located, say, 8" forward of the breech to accommodate a minimum 10-12" barrel, I think different diameters will be necessary to account for the difference in pressure impulses the piston will receive from a gas column that still has 16" of expansion to go, as opposed to one about to exit the muzzle.

I'm curious as well about where the op-rod goes, or how it works; it would seem like your desired gas-system length would put the tappet close enough to the carrier to favor a FAL-type arrangement. If you have any diagrams or drawings, I'd love to see them.

Take care,
Mike

Coolhand77

Well, I would post them, but I am kinda designing this and hoping someone will pay me for it later, so untill I have all the kinks worked out and get it patented its going to be a little vague on details. A good way to describe it (without giving away too many details) is a cross between the G36 tappet design and the M1 Carbine op rod design.

Okay, again I am going to get in the realm of assumption and theorizing. I belive the AK style piston (attached to op rod and bolt carrier directly) is simpler to manufacture, where as the g36 style (tappet/piston hitting op rod and pushing carrier) is lighter. Both (if built right) are robust actions. The only real difference between the AK and the FAL piston set up is the variable gas port and the fact that the FAL piston isn't directly attached to the bolt. Another example of this would be the Mini-14 or the M14. The op rod and piston are all one unit, but they are not directly connected to the bolt. The gas impinges direcly on the face of the op rod basically untill it moves far enough open the vent. the FAL does it by varying the size of the vent.

there are alot of ways to rig a short stroke and alot of them are VERY forgiving.

Part of the reason they redid the gas system on the Garand to make the M14 was that hotter loads would bend the op rod. This was a function of too much pressure at the muzzle and too long a rod, and the fact that it was under pressure for a longer period of time to cycle the gun. The shorter the rod, the stiffer the rod, the less chance it will bend. Also if you just use one hipressue tap to unlock the bolt and then let the residual recoil and chamber pressure cycle the bolt, you minimize the impact that variable gas pressures have on your operating system. The FAL was designed to vary the "tap" according to setting. My idea was to vary the tap by mission. The only caviat I would add to that would be a gas cut off switch for snipers using suppressors so that the bolt cycling wouldn't give them away. Then you just use the charging handle like a straight pull bolt action. If you have to go semi to disengage from the enemy, you don't sling your sniper rifle/DMR rifle and pull out a whole other weapon, you just set it to cycle normally and turn it into a long barrel assault rifle.

Versitility for the soldier is key to this design.

Essayons

Hmmm . . . I've poked around some Browning M1919 and M2 sites since I last posted. Interesting. I also plan to take a look at the Remington Model 8. I think Spartiate is right. There is a lot of potential for an updated recoil-operated design rendered in modern materials. His point about the M2's accuracy is excellent, as well. Recoil-operated weapons have accuracy potential.

Another thing I've been thinking about since I last posted is the ammunition component of the system. If the military requires shorter barrels (M4, XM8, etc.) the system should be optimized accordingly, with cases and powders that will provide the required velocity and accuracy out of the shortest posible barrel with the minimum flash and blast.

Another ammunition consideration is recoil impulse. A lower-impulse round like the 5.45x39 or the low-impulse round mentioned in The Black Rifle would increase hit probability and permit more latitude as to the method of operation (various delayed-blowback designs).

I'm still most interested in the potential of an lightened, updated BAR/FN-MAG-58 type action in an assault rifle. From what I've read soldiers universally heaped praise on the BAR and Garand in and after WWII and Korea.

Coolhand's point about the M14 are good ones, too. Most of the M14's inovations were product improvements (roller lug, alternative gas systems, etc) developed for the M1 Garand that were not adopted during WWII because Ordinance didn't want to compromize interchangeability.

Coolhand77

One thing I found out, quite by accident (because of the way its listed as a blowback), the P90 barrel moves rearward .3" befor stopping and "disengaging" from the breach block. Its never truely locked, but it is a delayed blowback action.
Can a recoil action be mated with an interchangable length barrel without changing the springs? If not its going to be an upper/lower setup like the AR15 and not just a barrel swap like I was planning. I was hoping that upper swaps would be just for different ammunition/feed options.

Spartiate

Hmmm . . . I've poked around some Browning M1919 and M2 sites since I last posted. Interesting. I also plan to take a look at the Remington Model 8. I think Spartiate is right. There is a lot of potential for an updated recoil-operated design rendered in modern materials. His point about the M2's accuracy is excellent, as well. Recoil-operated weapons have accuracy potential..

Thanks, Essayons. It's good to hear that my "sermons" on the recoil principle are getting good guns the attention they deserve. The 1919, in particular, is a fine example of a great design shunted aside in favor of a far-inferior gun because (despite a popular reputation as hide-bound conservatives) the military brass is much more likely, in almost every instance, to throw billions at the latest novelty or fad rather than dedicate a bit of thought and effort to improving what works--no one gets a Legion of Merit for "maintaining a sound pace of evolutionary development guaranteed to produce long-term combat effectiveness". Provided a QCB could be incorporated (admittedly, a considerable challenge), the 1919--an almost completely-unstressed receiver design--could easily have been made a great deal lighter than the POS M-60 (or, if we were willing to add a bit more weight for 1919-like reliability, we could simply have adopted your friend and mine, the FN MAG-58 (like everyone else in NATO), rather than waiting another 40 years.

You also wrote,
"Another thing I've been thinking about since I last posted is the ammunition component of the system. If the military requires shorter barrels (M4, XM8, etc.) the system should be optimized accordingly, with cases and powders that will provide the required velocity and accuracy out of the shortest posible barrel with the minimum flash and blast."

I agree, and plan to develop short-barrel loads when I get my Krinkov together. Something like Accurate 1680 would probably work well for the barrel lengths you mentioned, but I'll probably have to work with something faster--maybe Number 9. Wish me luck.

Take care,
Mike

Coolhand77

Essayons

Just posted my P90 inspired system in SAW/AutoRifle config on the Ideal AR thread. And as I stated there, I am pretty fixed on the gas system, but thats only cause I haven't figured out how to change barrel lenght on a recoil system with just a barrel swap.

I've been thinking about this using the AR15 upper as a frame of reference (see my recent post in the Ideal AR thread). What if you used a barrel shroud with a front mounted bushing a little shorter than the shortest barrel. The recoil system would be balanced to operate with the longest barrel. Shorter barrels would utilize a hybrid short-stroke gas/recoil system in which the bushing would act as an anular gas cylinder and the barrel as the piston (sort of like the boosters for other recoil operated guns - just not at the muzzle). Shorter barrels would simply have gas ports sized to operate the system reliably in all conditions (I'm sure easier said than done).

Before they reached their rearmost position the integral pistons on the barrels would be clear of the back of the bushing/cylinder to permit excess gas to escape into the barrel shroud (similar to the AK and other designs that exhaust, rather than cut-off excess gas).

The first major drawback I can think of is that the front of the bushing would require a precision fit for balance accuracy and functional reliability, but with the shorter barrels, it would be subject to gas fouling. You would have to make it easy to clean (i.e. removable from the shroud for cleaning).

Just a thought.

Coolhand77

I was thinking along the same lines, but the fouling issue came to mind as well. Just too many variables attached to weight and springs with that system. It might work if every soldier were an armorer and could pull that kind of double check in the field, but this design is for an "Everyman" gun. Kindof the same principle as the XCR but a different approach, "AK reliability and simplicity/AR accuracy and ergonomics". And Yes I know the posted stuff I did doesn't have AR ergo per say, but those are "prototyping" ideas that have since been superceded by an AR style safty/selector lever and pistolgrip. Even used some AR blueprints so I could get the angles and measurements right (though I am also developing a low profile "P90" grip for the PDW configuration and "Kalifornia" legal model.)

Essayons

I thought about this a little more, and it occurred to me that you might be able to integrate an adjustable gas system right on the barrel. Basically, it would be a ring with various size ports over a gas port the same size as the largest port. The ring would be held in place by another ring securely attached to the barrel. Ideally it could be adjusted with the tip of a bullet, but I'd settle for a special tool that could be attached to the weapon (in a buttstock compartment or pistol grip). The whole idea presumed a removable, if not QCB barrel.

This thread has inspired me to take a look at blow-forward (e.g. the Swiss AK53) action. It lacks the recoil reducing benefits of recoil operation, but has the potential advantages of simplicity and short OAL for a given barrel-length.

Coolhand77

Actually I was thinking a fixed piston smilar to the M1 carbine/G36 but with a three position switch. Position one would be normal, postion two would be for firing through fouling (emergency cycle when you don't have time to deal with a jammed weapon and you don't care if you frag it up as long as it does its job long enough to save your life or the lives of your mates), and postion three would be for "straight pull bolt action"/Rifle Grenade launching.

Of course the shorty wouldn't have the options, but since you change the piston/tappet with the barrel, thats no big deal. theoretically if your DMR goes down due to a malfunction, and you really need that DMR, you grab the barrel off the DMR (And the sight that is attached to the rail on the barrel) and slap it into someone's AR/CAR/PDW/IAR reciever and go back to doing the DMR thing.

Yah, you are down a rifle, but thats why I suggested PDW barrels for emergency backups. They are small and light (espcially with the fiber wrapped ultralight barrels) and HARD to bend/damage cause they are very well supported/protected by the upper reciever. Every soldier should keep one in is kit for emergencys (only adds one or two lbs and a hell of alot of feel good).

ps: Oh, and I was thinking that if the self cleaning piston idea I have works like its supposed to, then the gas system only has an on/off valve....and only on the longer barrels as you wouldn't be able to fit a rifle grenade on a PDW barrel...though it WOULD work on a CAR barrel.

Spartiate

Gentlemen,
I'm sorry for my non-responsiveness to your excellent posts; I've had duty the past few days, and gone to work an hour early (eliminating my "Forum Hour" in the morning :( ).

I saw Coolhand's latest diagram on IAR, but "field stripped" ;) this time. I'm with you 100% as regards intellectual-property protection. I want the best for our boys as much as the next guy (especially since I'm one of "our boys"), but I have boys of my own who will still need to eat once I drop anchor. I admit to a bit of frustration with Arne and Bill's proprietary policies when I first started looking into the Grendel (because they restricted outside entrepreneurs from innovating the sort of products that are just now coming on the market--like hi-cap magazines and affordable ammunition), but now I understand it completely: fame doesn't put a roof over your family's heads (when was the last time you saw an Ackley factory?).

I must agree with Essayons, though, when it comes to the positioning of that saddle-drum. Please explain what, in your bullpup design, differs ergonomically from the bullpup photos linked in Post 20, which place the shooter's face not merely "too close behind", but "right in the middle of" where the drum is depicted in your diagram.

I've seen a lot of doubt/questions on the difficulties of adjusting a recoil action to compensate for varying barrel lengths; I welcome all feedback (yea or nay) on the potential solutions posited in Post 22.

I think I can visualize your method of barrel-retention for a recoil-operated AR, Essayons. I don't think your muzzle-recoil booster should be excessively susceptible to fouling; the MG-3 issues described by Dobrodan regarded a belt-fed machine gun firing thousands of rounds at 20/sec. The booster area is certainly larger than a gas tube. I am curious, though, about the overall principle (since it seems like it would provide extra boost for shorter barrels, when the problem with shorter barrels is the need to attenuate rearward thrust in compensation for decreased inertia). Please elaborate on your method of breech locking and unlocking. I'd also appreciate a primer on the AK-53/blow-forward, with which I am not really familiar.

Thanks,
Mike

Essayons

I think I can visualize your method of barrel-retention for a recoil-operated AR, Essayons. I don't think your muzzle-recoil booster should be excessively susceptible to fouling; the MG-3 issues described by Dobrodan regarded a belt-fed machine gun firing thousands of rounds at 20/sec. The booster area is certainly larger than a gas tube. I am curious, though, about the overall principle (since it seems like it would provide extra boost for shorter barrels, when the problem with shorter barrels is the need to attenuate rearward thrust in compensation for decreased inertia). Please elaborate on your method of breech locking and unlocking. I'd also appreciate a primer on the AK-53/blow-forward, with which I am not really familiar.

My barrel retention method for a recoil operated AR is based on my experience with one-piece carbon-fiber free float tubes (e.g., Clark Custom Guns, DPMS, Hiperform). You'd just be adding the bushing/gas cylinder to the front.

The method of breech locking and unlocking would be very similar to a standarm M16. The difference would be the way momentum is imparted to the bolt carrier. My idea is to let the barrel and barrel extension travel rearward a short distance into the upper receiver to impart that momentum. I'm sure it wouldn't be as simple as shortening the threaded barrel extension area at the front of a standard upper to permit the barrel to move rearward - you'd probably have to fabricate a new upper - but that's the general idea.

The barrel, bolt and carrier would move rearward together until the barrel flange struck the front of the upper receiver and stopped. The bolt carrier would continue rearward, unlocking the bolt. When the bolt and carrier came back, they would close and lock the bolt and push the barrel to it's forward position.

Now that I think about it some more, it might not be workable as an AR conversion, because the way I have described it, the barrel extension would be too far to the rear in the barrel's rearmost position to permit feeding. A recoil operated upper would need to position the barrel extension in it's normal position for feeding and permit the bolt carrier to push the barrel farther forward from there...

I'm sure you are right about the barrel length issue. I'm new to this recoil operation stuff - just put the gas port on the longer barrels then.

I don't have much info on the AK53, except that it's one of two blowforward designs I know of (the other was a Steyr pistol). From what I've read, it sounds like it had both a reciprocating bolt and a reciprocating barrel. The powder charge was ignited when the barrel was still moving rearward.

It occurred to me that using a blowforward design with a heavy barrel might permit you to use more powerful cartridges than you could with a blowback design. A blow-forward weapon designed around a low impulse cartridge might be workable. If not you could retard the forward movement of the barrel (gas retarded blowback comes to mind) or use a locking mechanism (I have an idea here that would permit primary extraction).

Spartiate

My barrel retention method for a recoil operated AR is based on my experience with one-piece carbon-fiber free float tubes (e.g., Clark Custom Guns, DPMS, Hiperform). You'd just be adding the bushing/gas cylinder to the front.

The method of breech locking and unlocking would be very similar to a standarm M16. The difference would be the way momentum is imparted to the bolt carrier. My idea is to let the barrel and barrel extension travel rearward a short distance into the upper receiver to impart that momentum. I'm sure it wouldn't be as simple as shortening the threaded barrel extension area at the front of a standard upper to permit the barrel to move rearward - you'd probably have to fabricate a new upper - but that's the general idea.

The barrel, bolt and carrier would move rearward together until the barrel flange struck the front of the upper receiver and stopped. The bolt carrier would continue rearward, unlocking the bolt. When the bolt and carrier came back, they would close and lock the bolt and push the barrel to it's forward position.

I see now how this idea ties in to your earlier inertia-recoil posts. As a Benelli fan, I'd love to see the principle applied to a service rifle.

"Now that I think about it some more, it might not be workable as an AR conversion, because the way I have described it, the barrel extension would be too far to the rear in the barrel's rearmost position to permit feeding. A recoil operated upper would need to position the barrel extension in it's normal position for feeding and permit the bolt carrier to push the barrel farther forward from there..."

I think it might well be workable; it just might involve a few more new parts than originally envisioned. A new upper with a longer sleeve for the barrel, threaded for the retention-system you describe; maybe a longer extension to give more rear bearing surface . . .

"I don't have much info on the AK53, except that it's one of two blowforward designs I know of (the other was a Steyr pistol). From what I've read, it sounds like it had both a reciprocating bolt and a reciprocating barrel. The powder charge was ignited when the barrel was still moving rearward."
I Googled it and found some info here (http://www.swissrifles.com/pe57/index.html) . Not too descriptive, I'm afraid.

Take care,
Mike

Essayons

I think it might well be workable; it just might involve a few more new parts than originally envisioned. A new upper with a longer sleeve for the barrel, threaded for the retention-system you describe; maybe a longer extension to give more rear bearing surface . . .

Yep, you'd need to lengthen the upper ahead of the mag well. Normal uppers are already threaded for the barrel nut.

I have a vague recollection of reading about the AK53 in Small Arms of The World or something similar. I remembered it was Swiss and Googled "Swiss" and "blow-forward" to find the nomenclature and other info.

Coolhand77

Spartiate

Okay, this may sound really stupid later, but here it goes anyway.
One of the main gripes against a piston system is that with the rod attached to the bolt carrier, you have alot of mass along the length of the gun moving a little over the length of a cartridge, each time the weapon cycles. The Direct impingement gets rid of this by just jetting the gas back into the reciever area. I know this seems counter intuative, but why not go back to the SKS system? It basically uses a long tappet, which only moves a fraction of an inch, to hit the bolt carrier to unlock it and lets the residual blowback/recoil cycle the action after unlocking. Yes you have the additional weight of the tappet rod, but it does not connect directly to the bolt so it only moves a short distance, and you arn't blowing hot gasses, ccarbon, and powder fouling back into your reciever and face. Also you don't have a small tube with a tendancy for water to get into it and cause a rupture under pressure (gas tubes on ARs have been known to do this IIRC) or get clogged so easily. In addition, I belive the Simenov system had an adjustable porting system.
I'm probably telling yall something you already know, but it just seemed to click more than once while I was thinking about it.

As I've already mentioned (Post 377 on the "6.8-6.5" thread) I'm not convinced of the accuracy-spoiling effects of the off-bore-axis attached piston, which would be especially easy to mitigate in a bullpup design (by locating the vertical center of the recoil axis, a few millimeters above the bore axis, and placing the center of the buttplate/recoil pad directly behind it). It is also worth mentioning that a considerable advantage of the gas-piston action is the recoil-mitigating effects of the recoiling countermass (whereas the recoil action counteracts kick by being, essentially, its own shock absorber).

Nevertheless, I don't regard your idea as stupid at all--in fact, (since you have already explained your desire to use a tappet system) it seems like a natural progression of your design. To tell you the truth (and to return momentarily to the "historical design deconstruction" podium), I'd be happy to see you jettison the external op-rod--which I always regarded as a bit anachronistically first-generationish in the Garand, following as it did the modern-piston BAR and Lewis; odder still when retained in the M-14 (an otherwise superb design still in general Naval issue, with which I have had nothing but good experiences), a contemporary of the FAL, AK, and (!) AR-10; and IMHO much more trouble than it's worth for a 21st-century AR designer.

Take care,
Mike

Coolhand77

Spartiate

Oh, I had already done that, the op rod bending around to the side was for a different reason. In fact, with the epiphany about the SKS tappet, it simplifies the design even more.
My initial reason for using and "underbarrel to side of reciever" op rod (internal, with no external op rod sections) was to allow for the mechanism to feed from the top and eject out the bottom. The only issue now is how to link the charging handle since in my original design, the non reciprocating handle (which could be locked in recip mode for use as a bolt assist or bolt action mode) was to inpinge or lock on the forward section of the operating rod near the tappet/piston. My inspiration was the M1 Carbine and how without the stock, if the tappet werent there, the op rod could be used like a pump action.

That's a tough one, if you're dead-set against a linked gas/recoil system. In my opinion an op-rod, being horizontally asymmetric about the bore axis, is more likely to induce disruptive harmonics than an overbarrel gas system (off bore axis vertically), whether the piston's attached to it or not. How much recoiling mass is really saved by "cutting" the M-14's piston off? Personally, if my aim was an underbarrel piston gas action with top feed and bottom eject, I'd go with a hole in the piston/rod, like the BREN or M-60. I would locate the cocking handle around the junction with the piston (or where the tappet strikes the front of the op rod, if you'd like) and let it reciprocate (being far enough forward to clear both hands), allowing forward assist with no additional parts.

Take care,
Mike

Coolhand77

Spartiate

I will have to study the M60 and Bren diagrams a little, because I am not sure what you mean. Theoretically I can take a stock SKS action, cut off the charging handle, fabricate a new one that runs on either side of the tappet rod back to the bolt carrier, and then invert the whole system. Then all I have to do is see how short I can make the tappet to shorten the PDW/specops version. Since it is a top mounted piston/tube system as it exists now, inverting it would fit into my concept quite well.

Actually, come to think of it, I was wrong about the '60--it's a side-ejector.

Check out Essayons' Post 403 on the "Ideal Assault Rifle" thread, including a diagram of the M-240/FN MAG internals. It is a top (brass-to-the-grass belt) feed, bottom-eject gas-op gun, with a hole in the op-rod just forward of the bolt face for ejected casings. Although it is a piston gun, you could easily end the rod/carrier just forward of the opening, harden the forward face, and set it up to be struck by a tappet. Of course, both the SKS and the 240 use tipping bolts, meaning fully-stressed receivers, meaning a challenge to make barrels interchangeable (still not sure how it works on the 240). I'd use a similar concept, but with a rotating bolt/forward lugs.

Hope this helps,
Mike

Coolhand77

Thats why I was looking at the sks (stripper clip and ejects through the top so the op rod can't be in the way) and I think I figured out how do redesign the bolt for a two or three lug rotary.

Spartiate

Thats why I was looking at the sks (stripper clip and ejects through the top so the op rod can't be in the way) and I think I figured out how do redesign the bolt for a two or three lug rotary.
Aha--outstanding. Does the SKS eject straight out the top, or top-right (it's been a while since I shot mine)? I guess it really doesn't matter in a bullpup, since the stock should funnel spent casings more or less straight down.

Take care,
Mike

Coolhand77

Spartiate

exactly. I don't have an SKS...my current aquisition is a Vepr, but its on hold till June (Molot isn't shipping any civvie orders till then.). I might be able to scrape together enough for an SKS to study. It would be interesting to design a rifle around the an AK, but with the SKS tappet system. As for ejection, thats just a minor redesign of the ejector postion and extractor position on the bolt. Since we are redesigning from scratch, it doesn't matter.

"Scrape together enough for an SKS"? If you can afford your heating bill, an SKS should be a pittance ;)--yet another advantage of the rifle. About the only disadvantage it has, aside from the aforementioned fact that its tipping-bolt design stresses the whole receiver, is that its recoil spring--being behind the bolt rather than in the gas system as in the AK--requires a somewhat lengthy action. If you're willing to contend with that long of a receiver (not really a problem if you're looking at a bullpup), I think you may be on to something by working from the AK side toward an SKS tappet, rather than trying to re-engineer an SKS to use a rotating bolt. I don't know about your situation, but for me the prospect of "redesigning from scratch" would be daunting, if not impossible. I've looked at inverting an AK before (thinking in terms of belt feed), but shelved the project because I thought it would be too difficult; I was looking at how to work the recoil spring(s) around a slot for downward ejection (as discussed above) and decided it would be too difficult--but I think you're on a more viable track. If you take the AK carrier and lop off the recoil spring tube forward of the carrier proper, figure out how much spring-space you've lost in so doing (it looks like about 4") and lengthen the rear of the receiver accordingly, then tap the carrier for a hardened set-screw to take the impact of the tappet--voila, you're nearly there.

Take care,
Mike

Coolhand77

you know, considering the renewed interest in the Ultimax byt the USMC, I wish I could get my hands on one to see if I might just be able to adapt it to a Bullpupped AR.

Coolhand77

okay, quick luch post of an inverted Ultimax (I'll figure out how to solve ejection later) with a 50 rd P90 mag scaled up to 6.5 grendel size and bullpupped. Has A regular Ultimax with a 20 inch barrel below it for comparison. Also, the mech and barrel are taken directly so no length cheats with barrel shortening.

Spartiate

There were parts kits available a few months ago--and believe me, as a huge fan of constant-recoil in general and this design in particular, I'm kicking myself for my failure to acquire one in time. I haven't seen any for sale lately, and would bet that they've all been gobbled up by the company mentioned in the SW article. :(

Take care,
Mike

Coolhand77

Speaking of existing weapons systems that would be good for a Grendel conversion, I noticed in some shot show pictures that there was a Steyr AUG there, A3 variant I blieve. One of the shots was a close up of the manufacturers mark on the reciever and the address was a company out of West Point, MS. Does that mean we are going to have US manufactured AUGs available (or USRs for us non class 3 guys) in the near future? I belive that with a few minor tweeks the AUG would make a perfect platform for the 6.5G and even the .50 Beo. I wish I had one handy to reverse engineer since the design works already and could be adapted to my "oversized P90" concept quite easily.

Spartiate

Sadly, I have never handled an AUG, but (also sadly) I do have a "Speaking of existing weapons systems that would be good for a Grendel conversion" experience to relate. I had mentioned in the past (not sure which thread) that I'd like to try tinkering with an RPD. Except for dated ergonomics/construction and the lack of a quick-change barrel, I think it has many of the qualities desirable in a light machine gun--reasonably light weight and a feed setup that combines belt-fed capacity with a compact, unobtrusive drum that does not allow the ammunition to trip up the gunner or pick up grit. Its replacement, the RPK (also offering dated ergonomics/construction and the lack of a quick-change barrel), seems to have been adopted strictly for economic/logistical reasons rather than any tactical superiority over the older gun.

Being familiar (in principle) with the RPD design, I purchased a Centerfire Systems parts kit, unsure of where exactly the locking recesses were and hoping that enough of the receiver might be left to build an AKM-type trunnion-and-channel receiver. Unfortunately, while the kit is otherwise in superb condition, the bolt locks at the rear, and the recesses are behind the forward torch cut. I'm not sure whether it's worth shelling out for a semi receiver, sending the kit back, or keeping the parts for experimentation. Since it has a bolt-carrier like I mentioned in previous posts (with a slot for bottom ejection) I'm wondering whether there's any possibility of building some sort of Frankengun with a combination of AK and RPD parts. I've even considered the possibility of having a barrel-extension made and converting to recoil operation. Any suggestions you gentlemen might have would be greatly appreciated.

Thanks,
Mike

Coolhand77

I have a Vepr on order myself. Its based off the RPK reciever, and dimensions in an AK format, same ammo as the AK (easy conversion to Grendel probably), and they run around $600 (instead of 800 or more for an AR). I DO know someone with a preban AUG (not a USR), and I might ask him if I can strip it down and take measurements.

Essayons

Hey there - I've been thinking KISS - Blowback (or forward). After a little surfing I came accross the Oerlikon SSG36 - a blowback antitank cannon with a bolt extension that followed the rebated rim case (e.g. .50 Beowulf) into the chamber. In a blow-forward design, the barrel could cock a striker (a la Glock) when it returned to it's rearmost position. A blow forward design would use the mass of the whole barrel instead of a very massive bolt...

Coolhand, you should take a closer look at BAR and M240 diagrams. The receiver is stressed, which would increase weight compared to a rotating bolt in a barrel extension, but they were VERY reliable operating systems and interchangeable barrels were offered for both. As Spartiate points out, both systems are compatible with a tappet system...

Coolhand77

Spartiate

I've actually been considering that, though with a slight modification. The entire receiver need not be stressed, just the lock up parts and the rails that accomidate the movement of the bolt carrier. theoretically you could manufacture a "skeletonized" reciever and fill in the "holes" by moulding it into a polymer reciever

That shouldn't be very difficult. Since the placement of the locking shoulders on the RPD, and the total uselessness of the demilled receiver scraps supplied therewith, makes the possibility of reconstructing a historically-accurate replica a laborious proposition at best, I've been considering my alternatives. The Degtyarev design, like the M-240/MAG, uses tilting locking pieces (two, horizontally-opposed; the 240 uses a single vertically-deflecting lever) separate from the bolt, as opposed to an actual tilting bolt on the BAR, FAL, and SKS. One possibility is shortening the flaps to lock into a relatively-compact (say, AK-size, about 1.5") trunnion to permit quick-change, pre-headspaced barrel/extension assemblies. [In fact, as an aside, I'm considering whether substituting this feature for the MG-42's rollers could rectify one of that design's few deficiencies--the rollers require an extremely wide barrel extension, trunnion, and consequently receiver in order to function, leading to a great deal of extra weight.]

Back on topic, though, I can't think of any reason why a single, top- or bottom-locking shoulder couldn't be moved further forward on the bolt either, with a corresponding reduction in barrel-extension length, weight, and complexity--provided the extension is designed in such a way as to fully support the bolt head.

Take care,
Mike

Bill

Coolhand77

Personally I would love to start from scratch and develop a rifle, but I am also limited by a lack of resources. I don't however think we are going to get away from "slug throwers". "Beam weapons" need too much dwell time to cause significant damage. In fact rifles are a very efficiant "kinetic energy" delivery system. Bullets use a current aerodynamic projectile (of relitively simple construction) and spinstabilizing for accuracy and a chemical reaction for propulsion. You can change the peramiters of the cartridge (propulsion, mass, aerodynamics) but for it to be effective as a weapon you have to meet certain criteria. a smaller projectile needs a higher velocity to have the same energy potential, but then you run into the issues involved with an easily deflected projectile. By the same token, you can only go so large before recoil and cartridge weight become an issue.

Of course this all depends on what you want to do with the projectile. If all you want to do is take down a squirrel, then a light, fast projectile is enough, assuming good atmospheric conditions.

I personally think the 6.5 projectile envelope is close to perfect for a smallarm. At this point I would recommend instead of trying something totally new with the projectile (which we know works) improve the propulsion

I personally would start looking at caseless ammunition. Scaling up the G11s 4.7mm round to 6.5 (keeping the same proportions) would be my first suggetsion. In fact why not ressurect the whole concept of the G11, including the rotary chamber idea. since it was gas operated barrel length could also be variable for configuration and the bulk of your ammo load would be reduced to the total length of the bullet sitting on top of the primer (two stage ignition). In addition, extraction would no longer be an issue as the residue of the previous load is pushed out by the new round being pushed into the chamber. Also, the rotating chamber should imprve accuracy dince you don't have a pistoning action moving a great deal of mass back and forth.

Well, thats my thoughts on the subject. Wish I was in the industry so I could be in on the colaboration, but at this point I am only a broke enthusiastic computer aided drafter.

Oh, and by the way guys, keep up the good work.

Essayons

I am of the opinion that if we are to remain with systems that use kenetic energy to produce damage these should be optimized well beyond a spin stabilized hunk of lead before the weapon is considered.

Good point, Bill. Someone brought up the relative reliability of modern tools and appliances in another thread. If someone came up with a better KE solution than launching bullets out of a metalic cartridge through a rifled tube, I'd like to believe a reliable launcher would follow. Necessity is the mother of invention after all.

I can think of a few possibilities - saboted projectiles from a smooth-bore tube (borrowing from tank gun technology) and explosively formed projectiles spring immediately to mind. It would be really interesting to see if Metal Storm's stacked ammo concept could be combined with small ultra high velocity explosively formed projectiles to produce an effective burst fire weapon. Then there's the DREAD centrifuge weapon (http://www.google.com/search?hl=en&lr=&q=DREAD+centrifuge+weapon). Interesting concept.

Coolhand77

one issue that will slow the development of advanced projectile launchers is the reloading industry. With no case there is no way to "tailor loads" unless reloading becomes tinkering with the "powder block charges" and the bullets. I doubt Dynamit-Nobel and company are going to let just everyone have the secret of thier nytramine ammo bricks.

On that note, I can see the case being improved/changed to a polymer with brass or steel base. Also, improved powders and an improved chamber dynamics might allow for the same performance with smaller cases. some day we might actually be able to squeeze grendel ballistics out of a case the same diameter as the 5.56x45 (though the length would have to change due to bullet length). I have been wondering if that might not be possible with an acceptable pressure load in some other platform than the AR15.

Essayons

some day we might actually be able to squeeze grendel ballistics out of a case the same diameter as the 5.56x45 (though the length would have to change due to bullet length). I have been wondering if that might not be possible with an acceptable pressure load in some other platform than the AR15.

That's an interesting idea, Coolhand. I understand shorter cartridges tend to be more accurate (one of Grendels' strengths), but a skinnier cartridge would reduce bolt thrust and you could fit more rounds in a magazine of a given height and width. With the proper taper, they would probably made to feed and extract well.

Another unorthodox idea that has long interested me is Benjamin Flatau's tubular bullet technology. I came accross it first reading about research into ring airfoil grenades, which provided a flatter trajectory than conventional ones. IIRC, Flatau also came up with a tubulat .45 ACP round to "save" the 1911. Allegedly, in one test a goat wearing a kevlar helment was shot and the round penetrated both sided of the kevlar. For a while PMC marketed tubular copper UltraMag rounds, and tubular rounds are aleged to have been used by BATFE agents at Waco.

The cool thing about tubular projectiles is their performance against both hard and soft targets. They're supposed to cut out a tube through soft targets and bite and penetrate hard targets well.

Imagine something like a super-Beowulf that could shoot light, cheap high-velocity tubular rounds against point targets or miniature HE or HEDP rounds against area targets or materiel.

I think Bill was trying to get us to thing even further outside the box, though.

Essayons

Oh yea, one possible solution to the reloading technology hurdle would be to separate the projectile and propellant.

Liquid propellant has been discussed before, but you'd have to miniturize concepts that are at the bleeding edge of artillery technology.

Blocks of solid propellant would be another option. It would complicate feeding, but would provide a lot of flexibility.

A "diesel gun" is one idea that has occurred to me. With the bullet seated in the "neck" of the chamber, a piston would enter the chamber compressing the air therein. When the air was compressed, fuel would be injected and compression ignited in the chamber. How to do this in another matter - maybe revolving chambers with bullets fed from the front and the piston entering from the rear?

Coolhand77

My only issues with that would be seal leakage and an over complicated feeding system. That was the beauty of the G11. The feed system was relitively simple compared to some of the other "salvo fire" ideas. Not to mention, it was self cleaning as the next cartridge would scrape any residue out of the chamber.

Luso

A "diesel gun" is one idea that has occurred to me. With the bullet seated in the "neck" of the chamber, a piston would enter the chamber compressing the air therein. When the air was compressed, fuel would be injected and compression ignited in the chamber. How to do this in another matter - maybe revolving chambers with bullets fed from the front and the piston entering from the rear?

There is an old italian patent for this...
I guess its open source now... ;)

Essayons

It's also a well known phenomena among high-powered air gun shooters. It would be really cool if you could make it run on JP8 like everything else in the military, but I'm sure the gun (cylinder, piston and fuel supply) would have to be prohibitively large.

I just through out the explosively formed projectile idea a few posts ago, but if you could get the dispersion within useful limits and the recoil was not too great there might be potential there.

By the way, I just got a book entitled Rapid Fire tonight. I forget the author's name (will try to post it later), but it's got some good stuff in it. It is about the history of rapid fire weaponry in the .50 cal to 57mm range, which has undergone a lot of technical development in the last 60 years (more than small arms). Good stuff...

Daniel Watters

By the way, I just got a book entitled Rapid Fire tonight. I forget the author's name (will try to post it later), but it's got some good stuff in it. It is about the history of rapid fire weaponry in the .50 cal to 57mm range, which has undergone a lot of technical development in the last 60 years (more than small arms). Good stuff...

The author is Anthony G. Williams. He is the co-editor of Jane's Ammunition Handbook and the co-author of the Flying Guns trilogy and Assault Rifle. To be honest, I wouldn't be surprised that he lurks here from time to time.

Spartiate

Read this thread through twice before I thought I should post, there is some very good stuff here, but beware the very demons you seek to oust.

The premise of the thread (if I read it correctly) was that the field of small arms is constrained by its lack of interaction between scientific disciplines. This together with the political view of the subject has somewhat stagnated new and novel advances so here we all sit in this little backwater.

Bill Alexander

I'm honored to have the Man Himself on our humble thread, and grateful as well--having previously fallen to a certain degree under the sway of the "no single cookie-cutter cartridge" school of thought (http://www.geocities.com/equipmentshop/21stcenturyrifle.htm) and even designed a universal lower to take AR-15 and -10 uppers/mags interchangeably, I've been convinced by the members of this forum that the Grendel cartridge does in fact fulfill the present 5.56 and 7.62 roles quite admirably. Don't sell yourself short! I am especially grateful, because my idea for an optimized rifle design requires a short case in order to ensure reliable functioning.

I'm afraid, however, that I must respectfully disagree with your synopsis of this thread. While the point of view that "the field of small arms is constrained by its lack of interaction between scientific disciplines" and "here we all sit in this little backwater" may certainly have been articulated in this pages, those are neither my views nor the underlying premises of the Deconstructionist approach. Far from deploring a moribund state of the art and decrying a lack of revolutionary advances in small arms, I began the thread by expressing my skepticism that radical change in firearms development is even possible, stating that no such leaps have taken place in fifty years or more.

On the contrary, I believe (as I wrote in Post 8, to Essayons) that we are at roughly a 90% solution when it comes to small arms; that most sensible, experienced operators simply want certain improvements in their present weapons, or in other existing weapons; that nearly all those improvements have already been invented, or could be developed through minor alterations of existing designs; that it was in many cases a fondness for "new and novel advances"/change-for-change's-sake that led to the abandonment of certain weapons or features of weapons intrinsically superior (though perhaps less well-executed or refined) than their successors; and that, consequently, the present situation consists of a handful of OK operating systems optimized to their fullest potential, and a great many others--varying from barely-acceptable to damn-near-perfect--sidelined by outdated or wartime-emergency production values, but suitable for exploitation and development given a bit of thought and effort. The essential tone of this thread, therefore, is essentially conservative and historically-oriented, dedicated to the application of a capabilities-based approach to firearms development through the analysis, refinement, and synthesis of existing design features.

The Grendel cartridge by any consideration is a still an archeic design and while it may offer a certain level of refinement it is not in my view the best starting point for a new venture in small arms design. I am of the opinion that if we are to remain with systems that use kenetic energy to produce damage these should be optimized well beyond a spin stabilized hunk of lead before the weapon is considered.

An outstanding reductio ad absurdum of the gun; allow me to reduce it one step further: a firearm is no more than a device for holding a pipe bomb in such a way as to direct a single fragment in a (more or less) predictable direction; a more recent (historically speaking) development being to engineer the other fragment (the cartridge case) so as to seal the container and its user from blast effects. Nevertheless, I'll defer to one of Murphy's Laws of Combat, that "A stupid plan that works isn't a stupid plan." Grendelizer did an excellent job of defining the fundamental requirements for an Ideal Assault Rifle, but lets leave aside for a moment any preconceived notions of what the platform should be, and attempt to define what any primary individual weapon must offer. Its ability to engage point targets under field conditions must be at least on a par with the operator's (a function of human performance averages together with the time and resources available for weapons training). It ought to offer at least intermittent volume or burst capability for area targets, distant point targets, and suppressive fire. Most importantly, it must work the first time, every time (requiring both functional reliability and ergonomic fit with the typical operator). It cannot be too heavy for the operator (who, given today's diverse force, may be female and/or a member of a generally small-statured ethnic group) to carry all day in both hands; nor can it, together with all associated support equipment required for a mission, weigh more than its allotted share of the operator's overall carrying capacity (in pouches, packs, etc.). It must be sufficiently modular to accommodate (without exceeding the above weight parameters) whatever accessories are required to perform the above functions under all forseeable conditions; bonus points if a common chassis can interchangeably function as a fire support weapon, a precision long-range instrument for marksmen of greater skill and training, and/or a light, unobtrusive PDW/sidearm replacement for downed aviators, security, and second-echelon support troops.

Conceding the feasibility of producing our favorite science-fiction toys, but assuming that not only the laws of physics, but the range of human abilities and spectrum of materials within our forseeable/plausible productive capacity, remain in effect, what have fantasy's most brilliant minds conceived (in the realm of individual, man-portable weapons; leaving aside the debate on planet-vaporizing beam weapons for another day) that truly surpasses "a spin stabilized hunk of lead" vis-a-vis the above parameters? A lightsaber can deflect the single brief bursts of a laser blaster (all, even if such a weapon could be built, that any energy source could fuel), but what good would it be against the hail of death spewed by an MG-42 or Minigun, much less a belt of .303 fired indirectly from a Vickers sited a mile or two away, circa 1913? What would the best personal deflector shield avail the wearer against the sheer kinetic energy of a .50 cal, M-203 grenade, or RPG? Some of the futuristic-weapons posts attempting to address the questions you raised prove the point admirably: a comment on the DREAD gun article to which Essayons provided a link deduced that it would require a 600-horsepower electric motor, and no liquid fueled gun could produce solid-propellant power without liquid oxidizers--which I, for one, would not volunteer to carry into combat! I believe that, just as pre-hybrid electric car experimenters consistently failed to find any feasibly-refinable portable energy source comparable to primitive 19th-century internal-combustion engines burning icky old fossil fuels, weapons designers will be hard-pressed to exceed (or more importantly, to contain, since explosives far more powerful than smokeless powder have been available for over a century) the energy density of current small arms. Consider this lowest-common-denominator analysis, from a slightly-different perspective: the oldest, weakest cartridge still in common use--the .22 rimfire--puts a quarter-ounce of death into man's hands, for about two cents.

In conclusion, our present-day weapons measure up to individual-weapon standards quite admirably indeed, bringing the discussion back to the relatively-simple terms Grendelizer proposed. We want a weapon with the accuracy, feel, controllability, and ammunition weight of the M-16 with the long-range killing power of the M-14: Done, thanks to you and Arne. It needs to be more reliable: many believe this an unjust criticism, many others are working on quite-feasible solutions. ABS carbonfiber barrels seem to offer tremendous potential for increasing sustained fire, and modular systems are improving every day. There is one remaining problem in firearms design that remains a problem: some medieval genius strapped his handcannon to a two-by-four to keep the match out of his face and facilitate its use as a pike; ever since then, we've been unable to field a weapon that fits in a truck without punching out the window, fires rifle ammunition at advertised velocity, and shoots safely from both shoulders. Coolhand has his solution; I have mine, and many others have theirs. Whoever wins, we all win as long as shooters continue to consider the full range of firearms designs past and present with a view to optimize the weapons of the future.

Take care,
Mike