Kurz Wildcat?

In a Deconstructionist frame of mind (historical weapon ideas suboptimally implemented for political/economic reasons, then forgotten in favor of sometimes less-effective equipment, deserving a second look) it occurred to me that--had the Germans not been constrained to use 8mm barrel-making machinery in the StG-44, but had instead adopted the same cartridge in the 6-7mm window now regarded as optimum for intermediate rifle rounds--the first assault-rifle cartridge might possibly have been the last. I have often thought about the potential for such a cartridge (originally based on .45 Winchester Magnum brass, but actual Kurz brass is available, reasonably-priced, and constructed for rifle pressures), but rejected the idea based on magazine capacity considerations; however, as Stan pointed out during a discussion of the 6.5 OCC, the base area of a .445 case is only 12% less than that of a .473 case. If a .445", 7.62X39-based case has "the maximum dimensions that allow a double column feed" in a 5.56 magazine, might a .473" case be the upper limit for a magazine originally designed for the M43 cartridge? The Kurz case's taper might certainly be an advantage in this regard. If that's true (.45 ACP cartridges seem to stack up OK, though the wobbliness of the last seems to indicate follower mods might be in order--it's difficult to judge without the longer, tapered Kurz cases themselves, so I've ordered a few), the cartridge might offer superb, Grendelesque performance, subject to the following limitations:

-Somewhat-reduced capacity (26 rounds in a 30-round AK mag; 35 in a 40).
-Less versatility than Grendel (short, light varmint bullets firmly seated in the neck won't reach magazine length).

However, the following advantages might be possible:

-Ability to use the highest SD/BC bullets in a given caliber with zero intrusion into powder space, within the AR/AK magazine length limitation.
-A short, fat, efficient and accurate powder column.
-The slick, AK-like feed reliability of a tapered case.
-Compatibility, possibly requiring minor modifications, with cheap, ubiquitous AK magazines.
-Complete, unmodified compatibility with standard- and medium-length sporting rifle bolt faces, and with probably the most-common reloading shellholder (.308/.30-06/.45 ACP). This would offer the potential for buying a Savage or other caliber-convertible system as a "first deer rifle", then moving up later to a .308 or '06.
-The ability to use .45 ACP in an SMG variant with the same bolt.
-The ability to step up--using an MGI or other modular lower--to .308-based cartridges with the same bolt.
-The ability to use .45 Win Mag, loaded long with .45-70 or .458 Win Mag bullets, as the .50 Beo/.458 SOCOM-type bigbore twin for silenced work, brushbusting boars, penetrating engine blocks, etc. with minimal part-swapping.

I am developing a rifle action in which the shortest possible case is desirable for reliable ejection, and this seems like it might be just the ticket. Your expert commentary/questions/advice is wholeheartedly desired.

Thanks in advance,
Mike

That's an interesting idea, Spar.

I've had similar "what if" thoughts about the experimental .22 carbine developed by Ordnance. If we'd been willing to replace the BAR, Garand, Carbine and Grease Gun with the .22 Carbine and the M14, instead of trying to make the M14 do it all, would the Air Force have wanted M16s to replace their Carbines? (Of course the .22 carbine wouldn't have done anything for the 14's FA performance ;) )

There's really nothing new under the sun. In Popenker & Williams Assault Rifle there is a 1936 quoteation of a Russian designer proposing a 6.5mm intermediate round as optimal. He mentions the .25 Savage as an off-the-shelf option.

It would be interesting to see what would have been if logistical and political concerns hadn't derailed various attempts to optimize small arms ammo...

IIRC, you're a "recoil dinosaur." Can you tell us any more about this short action of yours withoug compromising your IP?

...it occurred to me that--had the Germans not been constrained to use 8mm barrel-making machinery in the StG-44, but had instead adopted the same cartridge in the 6-7mm window now regarded as optimum for intermediate rifle rounds--the first assault-rifle cartridge might possibly have been the last. I have often thought about the potential for such a cartridge...
An intriguing idea. If you're not already aware of it, according to Cartridges of the World, in the 1960s the 7.92 Kurz was wildcatted to .30 caliber. Obviously, this isn't as great a reduction in caliber as you propose, but it was a step in that direction.

One thing to consider: the 7.92 Kurz case has a rather short neck. To neck it down to the 6-7mm range without changing shoulder angle considerably will result in an extremely short neck. :(
If a .445", 7.62X39-based case has "the maximum dimensions that allow a double column feed" in a 5.56 magazine, might a .473" case be the upper limit for a magazine originally designed for the M43 cartridge?
Perhaps. However, I don't have an AK mag available, so can't offer a better opinion.
the cartridge might offer superb, Grendelesque performance...[and] the following advantages might be possible:

-Ability to use the highest SD/BC bullets in a given caliber with zero intrusion into powder space...
-A short, fat, efficient and accurate powder column.
-The slick, AK-like feed reliability of a tapered case.
-Compatibility, possibly requiring minor modifications, with cheap, ubiquitous AK magazines.
-Complete, unmodified compatibility with standard- and medium-length sporting rifle bolt faces...
-The ability to use .45 ACP in an SMG variant with the same bolt.
-The ability to step up--using an MGI or other modular lower--to .308-based cartridges with the same bolt.
-The ability to use .45 Win Mag, loaded long with .45-70 or .458 Win Mag bullets, as the .50 Beo/.458 SOCOM-type bigbore twin...
All but two of these points sound plausible. I'm somewhat doubtful that you can have "complete, unmodified compatibility with standard- and medium-length sporting rifle bolt faces" due to probable feeding difficulties in receivers designed for substantially longer cartridge cases. Also, standard AK mags may not prove usable. As with 6.5 Grendel and 6.8 SPC, your Kurz wildcat would more likely require a new magazine designed specifically for it.
I am developing a rifle action in which the shortest possible case is desirable for reliable ejection, and this seems like it might be just the ticket. Your expert commentary/questions/advice is wholeheartedly desired.
Oh...you wanted expert opinion? Never mind. ;) :D

If we'd been willing to replace the BAR, Garand, Carbine and Grease Gun with the .22 Carbine and the M14, instead of trying to make the M14 do it all, would the Air Force have wanted M16s to replace their Carbines?
I don't recall the timeline of events, but if the .22 Carbine came along at the right time, I'd say the Air Force would've been delighted to adopt it. They liked the minimal weight of the M1 Carbine, but needed a newer weapon and didn't want to replace it with the Army's not-nearly-as-lightweight "light rifle" (the M14). That's one reason why it was easy to sell the Air Force on the AR15 -- in its original form, it was almost the same weight as the M1 Carbine.

In a Deconstructionist frame of mind (historical weapon ideas suboptimally implemented for political/economic reasons, then forgotten in favor of sometimes less-effective equipment, deserving a second look) it occurred to me that--had the Germans not been constrained to use 8mm barrel-making machinery in the StG-44, but had instead adopted the same cartridge in the 6-7mm window now regarded as optimum for intermediate rifle rounds--the first assault-rifle cartridge might possibly have been the last. I have often thought about the potential for such a cartridge (originally based on .45 Winchester Magnum brass, but actual Kurz brass is available, reasonably-priced, and constructed for rifle pressures), but rejected the idea based on magazine capacity considerations; however, as Stan pointed out during a discussion of the 6.5 OCC, the base area of a .445 case is only 12% less than that of a .473 case. If a .445", 7.62X39-based case has "the maximum dimensions that allow a double column feed" in a 5.56 magazine, might a .473" case be the upper limit for a magazine originally designed for the M43 cartridge? The Kurz case's taper might certainly be an advantage in this regard. If that's true (.45 ACP cartridges seem to stack up OK, though the wobbliness of the last seems to indicate follower mods might be in order--it's difficult to judge without the longer, tapered Kurz cases themselves, so I've ordered a few), the cartridge might offer superb, Grendelesque performance, subject to the following limitations:

-Somewhat-reduced capacity (26 rounds in a 30-round AK mag; 35 in a 40).
-Less versatility than Grendel (short, light varmint bullets firmly seated in the neck won't reach magazine length).

However, the following advantages might be possible:

-Ability to use the highest SD/BC bullets in a given caliber with zero intrusion into powder space, within the AR/AK magazine length limitation.
-A short, fat, efficient and accurate powder column.
-The slick, AK-like feed reliability of a tapered case.
-Compatibility, possibly requiring minor modifications, with cheap, ubiquitous AK magazines.
-Complete, unmodified compatibility with standard- and medium-length sporting rifle bolt faces, and with probably the most-common reloading shellholder (.308/.30-06/.45 ACP). This would offer the potential for buying a Savage or other caliber-convertible system as a "first deer rifle", then moving up later to a .308 or '06.
-The ability to use .45 ACP in an SMG variant with the same bolt.
-The ability to step up--using an MGI or other modular lower--to .308-based cartridges with the same bolt.
-The ability to use .45 Win Mag, loaded long with .45-70 or .458 Win Mag bullets, as the .50 Beo/.458 SOCOM-type bigbore twin for silenced work, brushbusting boars, penetrating engine blocks, etc. with minimal part-swapping.

I am developing a rifle action in which the shortest possible case is desirable for reliable ejection, and this seems like it might be just the ticket. Your expert commentary/questions/advice is wholeheartedly desired.

Thanks in advance,
Mike


Could you post a pic/s of the Kurtz, M43, Grendel & WSSM?

In a Deconstructionist frame of mind (historical weapon ideas suboptimally implemented for political/economic reasons, then forgotten in favor of sometimes less-effective equipment, deserving a second look) it occurred to me that--had the Germans not been constrained to use 8mm barrel-making machinery in the StG-44, but had instead adopted the same cartridge in the 6-7mm window now regarded as optimum for intermediate rifle rounds--the first assault-rifle cartridge might possibly have been the last. I have often thought about the potential for such a cartridge (originally based on .45 Winchester Magnum brass, but actual Kurz brass is available, reasonably-priced, and constructed for rifle pressures), but rejected the idea based on magazine capacity considerations; however, as Stan pointed out during a discussion of the 6.5 OCC, the base area of a .445 case is only 12% less than that of a .473 case. If a .445", 7.62X39-based case has "the maximum dimensions that allow a double column feed" in a 5.56 magazine, might a .473" case be the upper limit for a magazine originally designed for the M43 cartridge? The Kurz case's taper might certainly be an advantage in this regard. If that's true (.45 ACP cartridges seem to stack up OK, though the wobbliness of the last seems to indicate follower mods might be in order--it's difficult to judge without the longer, tapered Kurz cases themselves, so I've ordered a few), the cartridge might offer superb, Grendelesque performance, subject to the following limitations:

-Somewhat-reduced capacity (26 rounds in a 30-round AK mag; 35 in a 40).
-Less versatility than Grendel (short, light varmint bullets firmly seated in the neck won't reach magazine length).

However, the following advantages might be possible:

-Ability to use the highest SD/BC bullets in a given caliber with zero intrusion into powder space, within the AR/AK magazine length limitation.
-A short, fat, efficient and accurate powder column.
-The slick, AK-like feed reliability of a tapered case.
-Compatibility, possibly requiring minor modifications, with cheap, ubiquitous AK magazines.
-Complete, unmodified compatibility with standard- and medium-length sporting rifle bolt faces, and with probably the most-common reloading shellholder (.308/.30-06/.45 ACP). This would offer the potential for buying a Savage or other caliber-convertible system as a "first deer rifle", then moving up later to a .308 or '06.
-The ability to use .45 ACP in an SMG variant with the same bolt.
-The ability to step up--using an MGI or other modular lower--to .308-based cartridges with the same bolt.
-The ability to use .45 Win Mag, loaded long with .45-70 or .458 Win Mag bullets, as the .50 Beo/.458 SOCOM-type bigbore twin for silenced work, brushbusting boars, penetrating engine blocks, etc. with minimal part-swapping.

I am developing a rifle action in which the shortest possible case is desirable for reliable ejection, and this seems like it might be just the ticket. Your expert commentary/questions/advice is wholeheartedly desired.

Thanks in advance,
Mike


Well, your wildcat cartridge already exists in the Improved version (30° shoulder) it's the .115-.120 short 22,6& 6.5BR. A 22-250 case aka 250 Savage case would have a similar amount of body taper, close to a Kurz if used with the same 19° shoulder angle. Also if a Savage styled case was used you could make the neck as long as you wanted.

Mike

Originally posted by Essayons

There's really nothing new under the sun. In Popenker & Williams Assault Rifle there is a 1936 quoteation of a Russian designer proposing a 6.5mm intermediate round as optimal. He mentions the .25 Savage as an off-the-shelf option.


Essayons, are you referring to Fedorov's Avtomat of 1916 ? - I know that was chambered for the 6.5mm Arisaka, but I thought Fedorov favoured the .25 Remington as an off the shelf option ?

There was the AVS-36 by Simonov, but I was sure that was chambered for 7.62 X 54 R mm . . .

http://www.gunsworld.com/reload/792kurz.html

That 7mm cartridge on the far left sure looks Grendelesque. Perhaps the British should be given credit more for the bullpup design than the 7mm cartridge.

Essayons, are you referring to Fedorov's Avtomat of 1916 ? - I know that was chambered for the 6.5mm Arisaka, but I thought Fedorov favoured the .25 Remington as an off the shelf option ?

There was the AVS-36 by Simonov, but I was sure that was chambered for 7.62 X 54 R mm . . .


No - Although IIRC Popenker and Williams also discuss the Federov in Chapter 1. I will try to remember to post the quote when I get home (unless someone else has a copy closer to their computer ;) )

I found this on pp. 11-12:
In 1930, the noted Russian gun historian, V.E. Markevich...suggested to the Army weapons command that:

The new "pistol carbines" should not be built around pistol cartridges, because of range limitations; instead such carbines should use a cartridge intermediate in power between the pistol and rifle cartridges. It is ridiculous to simply shorten the current rifle cartridge case and use the current (7.62mm) bullet for such cartridge, because of the rainbow-shaped trajectory and increased recoil. A true intermediate cartridge should be of 6.5mm calibre, and such a cartridge is already available in the form of American commercial .25 Remington cartridge.
Is this what you were thinking of?

Yep. That's it :)

I might try to find more info by/about Markevich. It would be interesting to know what he meant by 6.5mm. Did he mean .25, .264 or just "around 6.5 mm."

IIRC I read that Soviet research, like subsequent research by the Germans (to get back on topic), Brits and US, also concluded that a caliber smaller than 7.62 would be ideal, but went with 7.62 for logistical reason. I don't recall where I read it.

Well, I got the round right :p

I didn't know who said what or when they said it :o

Oh well, live and learn :D

An intriguing idea. If you're not already aware of it, according to Cartridges of the World, in the 1960s the 7.92 Kurz was wildcatted to .30 caliber. Obviously, this isn't as great a reduction in caliber as you propose, but it was a step in that direction.

Concur. I would guess that the modification was more a matter of taking advantage of the wider variety of .308 bullets in the US than of any perceived ballistic advantage for a .3mm reduction in caliber.

One thing to consider: the 7.92 Kurz case has a rather short neck. To neck it down to the 6-7mm range without changing shoulder angle considerably will result in an extremely short neck. :(

Thanks for the great advice. I'd have to push the shoulder back a bit to allow for more neck, although (theoretically, at least) a smaller-diameter bullet should not require quite as long a neck to seat firmly in the case.

I'm somewhat doubtful that you can have "complete, unmodified compatibility with standard- and medium-length sporting rifle bolt faces" due to probable feeding difficulties in receivers designed for substantially longer cartridge cases. Well, I did specify "bolt faces". Obviously, 2.25" cartridges would float around aimlessly under recoil in a .308 or 30-06 length magazine, and would require modification or blocking of the magazine to feed reliably, but that's a simpler proposition than bushing or machining out a bolt face for an uncommon rim diameter.

An additional bonus not mentioned in the first post is the possibility of trimming and forming cases from many of the most commonly-available parent cases on the market (.308, 30-06, Savage, etc. etc.) in a pinch.

Perhaps. However, I don't have an AK mag available, so can't offer a better opinion. . . standard AK mags may not prove usable. As with 6.5 Grendel and 6.8 SPC, your Kurz wildcat would more likely require a new magazine designed specifically for it. I won't be able to test the theory myself until Tuesday (when my cases are due to arrive). While it would certainly be beneficial (and a major selling point) if the cartridge could function from un- or minimally-modified AK mags, it is not absolutely critical. At this point (the "Basement R&D" phase), I am able to modify just about any existing component, but not of course to stamp or mold new magazines. The Grendel development process is a perfect example of how innovators were able to modify COTS equipment to work "well enough" to prove concepts that could be optimized for commercial, military, LE etc. sales once they had secured the backing and/or resources. I could test the overall feasability of a design even if I could only get a few rounds to feed from the AK mag (as opposed to, say, beginning with a completely-incompatible .492 diameter case head, or a 2.4" OAL).

Thanks,
Mike

Concur. I would guess that the modification was more a matter of taking advantage of the wider variety of .308 bullets in the US than of any perceived ballistic advantage for a .3mm reduction in caliber.
No significant ballistic advantage, to be sure. COTW says that .30 Kurz was developed for a modified M1 Carbine.
Thanks for the great advice. I'd have to push the shoulder back a bit to allow for more neck, although (theoretically, at least) a smaller-diameter bullet should not require quite as long a neck to seat firmly in the case.
Yeah, it's hard to say in advance of trial just how much neck it'd have, or how much would be needed for adequate support of the bullet. The Armourer's 6.5x39 has a very short neck, but apparently works okay.
http://www.65grendel.com/forum/showpost.php?p=333&postcount=1
I won't be able to test the theory myself until Tuesday (when my cases are due to arrive).
Oh...then you're serious about this project? Cool. I figured this was another one of those "fun-to-discuss-but-will-never-actually-be-done" projects. I look forward to seeing how it works out. :cool:

That's an interesting idea, Spar.

. . .

IIRC, you're a "recoil dinosaur." Can you tell us any more about this short action of yours withoug compromising your IP?

Essay,
Sorry it's taken me so long to respond. I'm actually split between short-recoil and gas-piston operation for a number of reasons (more on that in a moment). In either case, the basic platform is a bullpup chassis with upper and lower Picatinny rails (I don't see a reason for the bulk and weight of four) connected at the breech and muzzle ends. The factor dictating short cartridge cases is the ejection geometry, designed to facilitate full-time ambidexterity. That's all I'll say on that point for the moment, as it's the principal original feature of the design, and relatively easy to duplicate with existing technology (or even existing components).

While I prefer recoil operation, particularly of the MG-42 variety, it poses more challenges for a modular design, particularly when it comes to barrel interchangeability. Ideally my platform would accept barrels from PDW to DMR/LMG length, which would probably require adjustment to the unlocking dynamics in order to ensure safe, but reliable operation in a recoil design. I've speculated on a previous thread that the effect of a shorter pressure curve might counterbalance that of a lighter recoiling mass in a shorter barrel of equal diameter, but I have no means to test the theory. On the other hand, a modular gas-piston platform practically designs itself when I consider the areas for improvement in an AK, and the variety of components available today.

Take care,
Mike

Oh...then you're serious about this project? Cool. I figured this was another one of those "fun-to-discuss-but-will-never-actually-be-done" projects. I look forward to seeing how it works out. :cool:

W e l l . . . I'm serious about my modular weapon system project, although due to operational commitments I will have to wait at least a few more months to actually start making chips. On the plus side, that means I'll have a few more months to refine the details.

Regarding the wildcat, though, right now I can only offer a firm "that depends" ;) I'm obviously a Grendel fan, and there's no reason my design won't work in 6.5G. In fact, the only reason I devoted so much thought to the Kurz idea beyond the "historical what-might-have-been" stage was the fact that it crossed my mind during a bout of insomnia after a 0130 phone call. Right now, given the extremely basic nature of my shop and extremely limited amount of tinkering time at my disposal, the only way I'd add another variable / potential failure point to the project (not to mention the cost of custom reamers, dies, etc.) would be if AK mags seem compatible with few/no modifications. For my $16 investment in brass to date, and five minutes thumbing cases in and out of a magazine, that seems like a prospect worth investigating.

Thanks again,
Mike

Essay,
...snip...

While I prefer recoil operation, particularly of the MG-42 variety, it poses more challenges for a modular design, particularly when it comes to barrel interchangeability. Ideally my platform would accept barrels from PDW to DMR/LMG length, which would probably require adjustment to the unlocking dynamics in order to ensure safe, but reliable operation in a recoil design. I've speculated on a previous thread that the effect of a shorter pressure curve might counterbalance that of a lighter recoiling mass in a shorter barrel of equal diameter, but I have no means to test the theory. On the other hand, a modular gas-piston platform practically designs itself when I consider the areas for improvement in an AK, and the variety of components available today.

Take care,
Mike

Good to see someone tilling this ground. When I first examined the Grendel cartridge about 3 years ago now I immediately thought of the MG-42 short-recoil action. The short Grendel case should allow a very high ROF and softer recoil as less energy needs to be harnessed on a log scale as the distance the barrel & bolt assembly must travel is shortened. I think it might be possible to unlock the bolt while there is still some pressure in the barrel to help the spent shell casing break free of any barrel weld. Also, since both the barrel and the bolt are traveling backwards at the same speed before they unlock there should be few extraction or extractor failures as the relative speed between them is significantly less than with gas operation. I wish you the best of luck on this project. If I had a facility to work from I'd offer to help but as it is I don't. I was focused on a Grendel MMG, but your project sounds very promising. Best of luck.

Roy

Good to see someone tilling this ground. When I first examined the Grendel cartridge about 3 years ago now I immediately thought of the MG-42 short-recoil action. The short Grendel case should allow a very high ROF and softer recoil as less energy needs to be harnessed on a log scale as the distance the barrel & bolt assembly must travel is shortened. I think it might be possible to unlock the bolt while there is still some pressure in the barrel to help the spent shell casing break free of any barrel weld. Also, since both the barrel and the bolt are traveling backwards at the same speed before they unlock there should be few extraction or extractor failures as the relative speed between them is significantly less than with gas operation. I wish you the best of luck on this project. If I had a facility to work from I'd offer to help but as it is I don't. I was focused on a Grendel MMG, but your project sounds very promising. Best of luck.

Roy

Thanks for the words of encouragement, Roy. I find the MG-42/MG-3, as designed, to be equal to any weapon in its class and superior to most. The only real problem with the current variant is mass and bulk: the receiver is the size and weight of a signpost; of course, it's made from the same mild steel as a signpost--a limitation imposed by materials shortages by which WWII Germany was constrained, and we are not--and simply specifying modern materials would help a great deal in this regard, as would Grendelization (or Kurz-ization, for that matter, which would allow the use of the standard bolt head). That much is self-evident, and has been discussed several times in the past.

I'd go a few steps further, given the time and resources. The basic action of the 42 is conducive to bullpupping, being a bottom-ejector already; the 42 itself (or a Kurz derivative thereof) less so, due to the bulky feed cover dictated by its relatively-fat case head. A Grendel, by contrast, could use a feed cover the size of an RPD's, which is trim and--if made of polymer and Hogue OverMolded--would be quite serviceable as a cheekpiece, given the addition of a guide to prevent unwelcome belt-to-chin friction :( . Replacing the slotted-tube barrel shroud with two or three Picatinny rails would make the weapon amenable to most modern optics and accessories, and take the 42's bipod versatility (forward mounting for precision or aft to facilitate traverse) one step further. If employed solely as an open-bolt LMG, it could also be modified to use the grip/trigger assembly for cocking, eliminating the bulky handle while retaining positive control of the bolt despite gloved or wet hands. Rather than boost the ROF further, I'd utilize constant recoil to permit extremely controllable fire despite the weapon's light weight.

The MG-42 is known for superb initial extraction for the reasons you mentioned, as well as the gentle camming effect of the unlocking rollers. I have given a great deal of thought to improving the recoil dynamics further by employing eccentric roller(s), imparting a gradual-to-sharp energy transfer from barrel to bolt, similar to the effects of a toggle (i.e. Maxim, Vickers, Furrer) or accelerator (BMG). The challenge is making it all fit in a relatively-compact package--as much a machining problem as an engineering problem.

Take care,
Mike

Mike,

A couple of things I wanted to add here. First, for making large monolithic parts out of Ti Google around and check out superplastic forming. In essence it allows many metals to be formed like plastic without detempering them. Ti is a very special case as it is extremely abrasive and kills machine tools in short order. Because of this making Ti parts out of billets and them machining them is very expensive. I'm not sure about the roller guides for an MG-42, but from what I know of the M240 I am almost certain the entire receiver could be made using this process with little or no backend machining required. (there might need to be a steel barrel plug which accepts the QCB inside and has a coarse threaded outer surface that screws into the Ti receiver to reduce machining to a relatively coarse thread clean-up)

Diffuse bonding is a process where the outside and the inside of the part can each have “machined” finishes and in-between there is a metal mesh. In broad strokes it works like taking two pieces of warm taffy, pressing them against each other through a wax-paper pattern and them pulling them slowly apart. What you are left with is a 3-D object with two finished sides and a porous metal sandwich in-between. I don’t know what state-of-the-art is currently, but I can tell you that my contacts considered a mono-hulled PAV (4’x4’x5’x9’ Ti armored hull) to be a piece of cake. They are making Ti turrets for the Stryker at the request of the Army (Rangers ??? – not sure now) as a mono-pour to take a ton or so out of the weight and make it tougher in the bargain so the PAV hull should be easy.

If you decide to pursue this and need a contact to help you mfg such a part give me a PM. I have a good contact in this industry.

The 2nd thing is you might want to investigate is electric damping of the recoil. If you embedded one or more rare-earth magnets in the bolt and had a copper or aluminum coil (aluminum with gold cladding would be my vote) wound under the bolt's line of travel you would produce an electrical charge. If you shorted that charge into a resister you would have a 1-2lb controllable recoil attenuator. You can demo the process to yourself by twisting a common electrical meter in your hand with and without a piece of wire shorting the terminals. The fact that a variable amount of energy can be sucked out of the bolt makes it able to compensate for temperature, a dirty recoil amplifier, different bullet weights and rates of fire. You might also decide to harness the electricity to recharge batteries or power optics.

[Y]ou might want to investigate . . . electric damping of the recoil. As a computer guru and sci-fi writer, you can be forgiven ;) your techie approach to firearms design. As a cutlass-and-boarding-pike sailor by disposition, a naval tactician and planner by professional choice, but more often than not a professional babysitter of finicky electronic gadgets in reality, I understand the indispensability of tron-heavy solutions against modern, complex threats (i.e. antisubmarine warfare, supersonic seaskimming missile defense), but default to KISS solutions wherever possible, and instinctively distrust most equipment dependent upon juice (particularly of the battery-operated variety--the bane of the Mk44). To paraphrase a great "fleet" saying, ". . . [T]echnological terror . . . is nothing beside the power of the Force" (where the Force in question is the chemical energy of gunpowder harnessed by simple, reliable, mechanical means, that is) :D

For making large monolithic parts out of Ti . . . IMHO, from a manufacturing standpoint one of the greatest advantages of the MG-42 (and AK, the other action I'm considering) is the absence of large, monolithic parts of any metal--except for the trunnion, which (owing to the fact that it dictates a bulky, cumbersome receiver and transmits part of the recoil force directly through the receiver walls) I'd like to engineer out by using unlocking piece(s) sprung rather than welded or riveted to the receiver.

If you decide to pursue this and need a contact to help you mfg such a part give me a PM. I have a good contact in this industry. I know from previous posts you share my interest in firearms applications of high-temperature carbon fiber composites. I've done a fair amount of CF work in the past, but only hand layup using standard low-temp resins for marine applications. I have a few ideas both for high-temp resins and for simplified benchtop injection molding, but if you have any contacts in this field, I'd appreciate that information.

Thanks again,
Mike

..but there's nothing electronic about an electric motor. Electric motors have been around as long as the gas-operated machine gun.

..but there's nothing electronic about an electric motor. Electric motors have been around as long as the gas-operated machine gun.

As mentioned in my previous post, I "instinctively distrust most equipment dependent upon juice", electric or electronic. There's little or nothing electronic about the Mk44, but it's still unreliable due to its dependency on batteries and battery chargers (why, when we always deploy it from the back of a floating powerplant, it hasn't yet been adapted to AC is beyond me). Juice + saltwater = bad; throw in the beating to which a firearm is subject (or any heavy machinery; just yesterday I had a run-in with a milling machine whose mechanical components give an Abrams tank a run for its money, but whose poorly-protected wiring didn't survive the trip from curb to basement), and I'll go for the solid reliability of bolts, levers, springs, etc. any day.

Mike

Spar, I spent some time daydreaming about the ideal assault rifle on a hike this Sunday. I was thinking the US trend toward short barrels (M4, XM8, etc.), suggests a short fat case and fast burning powder for a short "all burnt" distance (within pressure constraints). A bore larger than 5.56 would help, too (more volume). Experimentation would be required to determine the ideal caliber for a given set of requirements, so let's just call it 6.5 for now ;)

Then I started thinking about the action. It would have to be strong enough to handle a high pressure round. I've thought a lot about a gas-boosted recoil system like the MG34 and 42 with the gas boost moved to the rear. The barrel contour would incorporate an integral annular "piston" and the forward bushing would form the cylinder. That would permit barrels of various lengths and weights, because each barrel would have the appropriate size gas port(s).

I dismissed that system and most of the other recoil systems I've read or though about, due to the great reciprocating mass and because I think the standard infantry weapon needs a fixed barrel for a couple reasons (mounting bayonets and other accessories and to remove a possible source of malfunctions - physical interference with the movement of the barrel). I know a full-length barrel sleeve can address these concerns, but that means sleeves of various lengths for barrels of verious lengths).

I pretty quickly came back to gas operation and a bropped (BAR M240) or rotating a two-to-four lug bolt. I just got done reading US Army Weapons Command Technical Notes: Small Arms Design, which confirms my prejudice in favor of designs that incorporate primary or initial extraction. (Great book for the money, BTW.) Both propped and rotating bolt designs can provide primary extraction, but front locking rotating bolt designs tend to be lighter.

US Army Weapons Command Technical Notes: Small Arms Design confirms the lugs on rotating bolts are typically not cut at 90 degrees from the bolt's axis. They incorporate a helical angle of 4 degrees or less. As they unlock, the case is extracted a few thousandths before it was extracted all the way. That primary extraction loosens the casings in the chamber. You could do the same thing with a Johnson/Stoner bolt, but the rotation of the bolt is so small that the rearward movement of the casing would be insignificant. Johnson/Stoner bolts lack primary extration. (IMO that and a relatively straight case are bigger problems than direct gas impingement.)

I'd probably opt for a short stroke gas tappet system to minimize reciprocating mass. Based on what I've read, I'd probably go with a White gas cutoff and expansion system like the M14's or M60's, but with looser tolerances than the M14's system.

I could go on, but long story short, I think there are many reasons that so many small arms designers have arrives at a short fat case, gas-piston operation and front locking two lug bolts (three in the case of the XCR)...

Disclaimer: I am not an engineer, let alone a small arms designer. I'm just a CPA who is way too interested in this stuff and read as much as I can about it between work, raising three kids and building and shooting ARs and other hobbies ;)

As mentioned in my previous post, I "instinctively distrust most equipment dependent upon juice", electric or electronic. There's little or nothing electronic about the Mk44, but it's still unreliable due to its dependency on batteries and battery chargers (why, when we always deploy it from the back of a floating powerplant, it hasn't yet been adapted to AC is beyond me). Juice + saltwater = bad; throw in the beating to which a firearm is subject (or any heavy machinery; just yesterday I had a run-in with a milling machine whose mechanical components give an Abrams tank a run for its money, but whose poorly-protected wiring didn't survive the trip from curb to basement), and I'll go for the solid reliability of bolts, levers, springs, etc. any day.

Mike

Yeah, I owned a nice boat once and watched those sacrificial zinc anodes like a hawk. This actually was helpful in the design of the PAV because like you I don't think electric wheel motors and salt water are ever going to be a good idea. This is one of several reasons I chose hydraulic wheel motors for the PAV. The 3-5,000psi pressure against the seals pushes salt water, dust, mud, etc out away from machined surfaces. The seals weep a very tiny amount so you have to add a pint a year to a backhoe's 14 gallon reservoir but its a small price to pay for the reliability you get.

The recoil anntenuator I described is actually a linear generator but only generates power when the bolt is moving. About the only thing in physics more basic than generating electricity by cutting magnetic flux lines with wire windings is gravity. It is totally reliable. This design has no moving parts and the coil would be embedded in the receiver and normally is baked into a ceramic insulator in commerical applications. This leaves only the potential of the magnet to fail under extreme heat. I just wanted to let you know I was being a bit sloppy before in my description. That said, I respect your choices and will be interested to follow the development and modernization of my favorite machine gun. Best of luck!