Ideal Assault Rifle

issue I have with the HK roller delay blowback system that is that you have to have a much more massive bolt carrier than you really need
I am speaking from experiance as a former HK91 owner. Its also finiky enough that it needs flutes in the chamber to aid with extraction...not good.

It would appear that the answer is a little more complex than "do this and that to get the perfect combination".
While a bullpup would be a benefit due to the longer barrel, it introduces a few issue, some of which have already been mentioned. First is the ability to switch from right to left hand versions.
As have potential solutions--ejection out the bottom or (as demonstrated to virtually unanimous acclaim in the FS2000) forward.
Second issue is that to design a universal weapons system such as the Chinese recently attempted to do with their 5.8mm chambered weapons, would require a conventional AR design - as it is dang near impossible to design a proper LMG on a bullpup design.
Please elaborate. If you're talking about the ability to perform in the AR role as well (i.e. feed from both belts and magazines) I agree that it is a challenge; but a pure, belt-fed LMG may be the most readily convertible of all to bullpup configuration (if performance in the AR role is not required/desired) for two reasons. First, a belt gun is a low-profile top feeder that can (and in some cases does) eject ambidextrously out the bottom without the interference of a magazine (links are shuffled out gently and do not pose the same issues as ejected casings). Second, the other major challenge in bullpup AR design is crafting a fire-control mechanism that retains some semblance of feel and crispness over a long linkage between trigger and sear; in an open-bolt LMG, with its gas/recoil system under the barrel, simply placing a standard FCG forward of the ejection port, and machining a sear notch at the appropriate point on the op-rod, would eliminate such a linkage entirely. The RPD in particular is superbly suitable for such a project, having all the desirable characteristics described above in addition to robust simplicity, light weight, and a proven (and Grendel-compatible) chambering. Perhaps most importantly, it has a narrow/unobtrusive feed mechanism wanting only a rubberized cheekpiece to allow cartridges in and links out under the gunner's chin (as much as I love the MG-42, its feed cover for the fatter 8mm and 7.62X51 cartridges is almost twice as wide). I have a parts kit and would love to do a semi-build when time permits, although I'd obviously have to forgo Advantage II for legal reasons.

Take care,
Mike

While a bullpup would be a benefit due to the longer barrel, it introduces a few issue, some of which have already been mentioned. First is the ability to switch from right to left hand versions. Second issue is that to design a universal weapons system such as the Chinese recently attempted to do with their 5.8mm chambered weapons, would require a conventional AR design - as it is dang near impossible to design a proper LMG on a bullpup design.
How about going in between the two extremes and have a "semi-bullpup" weapon system?

The FG42 rifle and M60 machine gun are examples of semi-bullpup configurations that combine shorter overall length than conventional designs, without the ejection difficulties of bullpups.

How about going in between the two extremes and have a "semi-bullpup" weapon system?

The FG42 rifle and M60 machine gun are examples of semi-bullpup configurations that combine shorter overall length than conventional designs, without the ejection difficulties of bullpups.

Bullpups don't have "ejection difficulties" per se; they have ambidexterity difficulties--magazine, ejection port, and a left-handed shooter's face trying to occupy a finite amount of space around the weapon's receiver :eek:. The FG42, with a massive magazine protruding from its right side, is far from ambidextrous :p; while I've never shot an M-60 left handed, I don't believe it has a brass deflector, and don't intend to try ;). A better example might be the MG-42, a bottom ejector with a stubby buttstock like the M-60's.

In all of these three cases, longer-than-average recoiling masses reciprocate through part of the area normally occupied by the buttstock; the same might be said of an AR-15. None of these weapons are appreciably shorter than conventional rifles firing similar cartridges, where length is determined by the sum of barrel length, magazine depth fore and aft, length of pull, plus another couple inches for the barrel extension/trunnion, magazine release, and shooter's finger.

The closest thing to a successful (ambidextrous ejection with a short overall length to barrel length dimension versus similar-caliber weapons) "semi-bullpup" I can think of off the top of my head is the Calico carbine/SMG. Of course (as I believe others on this thread have mentioned earlier), a helical magazine feeding front to rear would make for a successful true bullpup design (although with any helical magazine, capacity would be limited with full-length rifle cartridges).

Happy New Year,
Mike

Bullpups don't have "ejection difficulties" per se; they have ambidexterity difficulties--magazine, ejection port, and a left-handed shooter's face trying to occupy a finite amount of space around the weapon's receiver :eek:. The FG42, with a massive magazine protruding from its right side, is far from ambidextrous :p; while I've never shot an M-60 left handed, I don't believe it has a brass deflector, and don't intend to try ;). A better example might be the MG-42, a bottom ejector with a stubby buttstock like the M-60's.

In all of these three cases, longer-than-average recoiling masses reciprocate through part of the area normally occupied by the buttstock; the same might be said of an AR-15. None of these weapons are appreciably shorter than conventional rifles firing similar cartridges, where length is determined by the sum of barrel length, magazine depth fore and aft, length of pull, plus another couple inches for the barrel extension/trunnion, magazine release, and shooter's finger.

The closest thing to a successful (ambidextrous ejection with a short overall length to barrel length dimension versus similar-caliber weapons) "semi-bullpup" I can think of off the top of my head is the Calico carbine/SMG. Of course (as I believe others on this thread have mentioned earlier), a helical magazine feeding front to rear would make for a successful true bullpup design (although with any helical magazine, capacity would be limited with full-length rifle cartridges).

Happy New Year,
Mike

The FG42 has its magazine protruding from the left side...

Also, there is another possibility, something I sketched up a long time ago (and it may be mentioned earlier in this thread):

http://i32.photobucket.com/albums/d19/dobrodan/drawing2.jpg

Bullpups don't have "ejection difficulties" per se; they have ambidexterity difficulties--magazine, ejection port, and a left-handed shooter's face trying to occupy a finite amount of space around the weapon's receiver.
And those characteristics don't cause any ejection difficulties with bullpups? :rolleyes:
The FG42, with a massive magazine protruding from its right side, is far from ambidextrous...
Uhh, the FG42's magazine extends from its left side. Since the "massive magazine" poses no problem for right-handed shooters, I rather doubt that it'd trouble southpaws. :p
...while I've never shot an M-60 left handed, I don't believe it has a brass deflector, and don't intend to try.
That's okay. Plenty of others have shown that it's safe to fire M60s left-handed. A couple of examples attached below. The bottom one shows the most extreme rearward ejection angle I've seen. On most photos, cases eject at a 90-degree angle.
In all of these three cases, longer-than-average recoiling masses reciprocate through part of the area normally occupied by the buttstock; the same might be said of an AR-15.
Yes. So what?
None of these weapons are appreciably shorter than conventional rifles firing similar cartridges...
The M60 is almost 5 inches shorter than the M240B, slightly less than the difference between the lengths of the M16 rifle and M4 carbine (with stock extended).

None of these weapons are appreciably shorter than conventional rifles firing similar cartridges...

Even the M4 is at least 5.5" shorter than the M16, and even though on paper, the difference isnt big, in practice it is.

Also, there is another possibility, something I sketched up a long time ago:
Details of your drawing don't show up well on my monitor. Do you have the magazine inserted into the grip? Or is the mag well on the left side of the weapon, with a space between the grip and magazine?

Details of your drawing don't show up well on my monitor. Do you have the magazine inserted into the grip? Or is the mag well on the left side of the weapon, with a space between the grip and magazine?

It is inserted into the grip. This will require an unorthodox way of holding the gun, but with a knob for the thumb (to countergrip), it should be quite pleasant to use.

Also, it should have a push-safety on the thumbgrip, and the selector built into the trigger like the AUG (push a little bit for single shots, and push more for auto)

I see. That 's similar to the Interdynamics MKS, which had its... ...box magazine serving as a pistol grip. This layout resulted in shorter overall length when compared to conventional rifles with the same barrel lengths, but seriously compromised ergonomics. Because the standard 5.56mm magazine is significantly deeper (front to back) than a typical pistol grip, the firing hand's hold and a trigger reach were far from being comfortable.
http://www.world.guns.ru/assault/as62-e.htm

I first saw a photo of the MKS some years ago. Initially I thought the design had promise, but then I tried holding an M16 magazine as if it were an MKS pistol grip. I have to concur with Max Popenker's comments about this configuration, and doubt that it'd ever gain acceptance among either civilian shooters or military personnel.

Except for cartridges of short overall length, like pistol ammo, it looks as though the bottom-feed magazine is not really compatible with this approach. It's unfortunate, since your use of a semi-bullpup layout overcomes some of the more significant drawbacks of the bullpup configuration.

Perhaps top-feed would work better? Maybe a longitudinal box mag, a la FN P90? Or an inverted C-Mag?

I see. That 's similar to the Interdynamics MKS, which had its...
http://www.world.guns.ru/assault/as62-e.htm

I first saw a photo of the MKS some years ago. Initially I thought the design had promise, but then I tried holding an M16 magazine as if it were an MKS pistol grip. I have to concur with Max Popenker's comments about this configuration, and doubt that it'd ever gain acceptance among either civilian shooters or military personnel.

Except for cartridges of short overall length, like pistol ammo, it looks as though the bottom-feed magazine is not really compatible with this approach. It's unfortunate, since your use of a semi-bullpup layout overcomes some of the more significant drawbacks of the bullpup configuration.

Perhaps top-feed would work better? Maybe a longitudinal box mag, a la FN P90? Or an inverted C-Mag?

What made it feel uncomfortable? Was it not the angle of your wrist?

I feel that the gun would be a bit more comfortable with "my" angled handgrip... Notice that I did not intend that the thumb should be wrapped behind the magazine, but rather that it should rest against a knob on the side of the gun.

Another point of having the angled hangrip is that it moves the hand closer to the center of gravity, improving one-handed handling of the gun.

It's been a number of years, so I don't recall all of my impressions. Since I was trying to emulate the MKS grip, I think I just tried to hold the magazine in the same manner as a conventional pistol grip.

I was basing my remarks on mentally envisioning what your grip design might feel like. To properly evaluate your concept would require handling an actual mockup of a rifle so-configured.

Weight & Balance:
Conventional (Lightest/Good) -- Semi-bullpup (Intermediate/Fair) -- Bullpup (Heaviest/Poor)

Overall Length:
Bullpup (Shortest) -- Semi-bullpup (Intermediate) -- Conventional (Longest)

Length of Pull:
Conventional (Nominal/Adjustable) -- Semi-bullpup (Nominal/Adjustable) -- Bullpup (Excessive/Fixed)

Uhh, the FG42's magazine extends from its left side. Since the "massive magazine" poses no problem for right-handed shooters, I rather doubt that it'd trouble southpaws. :p ).
Congratulations on "catching" that a mere six hours after Dobrodan had already pointed it out :p. I stand corrected regarding the M-60, although the shooter in the picture where you can see the ejection port does seem to be shying back a bit further than I would position my head naturally (shooting right handed), and with the empties where they are I bet he's grateful for that eye protection ;). I'd be interested if you had a picture of someone shooting the FG42 left-handed, since its ejection port seems well aft of the 60's.

The M60 is almost 5 inches shorter than the M240B, slightly less than the difference between the lengths of the M16 rifle and M4 carbine (with stock extended).

That's true, although 2 3/4" of that is barrel length; the Mk48 is a conventional design (feed chute fully forward of the trigger guard), and is 2" shorter than the 60 (1" discounting barrel length). My point was simply that a conventional rifle layout, while advantageous in many respects, imposes a minimum-length constraint on the designer (barrel length plus 19-20" or so for a 7.62 NATO). If one can overcome that limitation by going to a semi-bullpup layout, the tradeoff may be worthwhile; otherwise it seems pointless to forgo some of those advantages--particularly as regards belt-fed machine guns, which (as I mentioned earlier) are ideal platforms for bullpup configuration.

Take care,
Mike

Congratulations on "catching" that a mere six hours after Dobrodan had already pointed it out :p.
I may not be fast, but at least I'm not half-fast. Do you expect me to be in the forum 24 hours per day, so as to immediately read a posting from halfway around the world? :p right back at ya.
I stand corrected regarding the M-60, although...with the empties where they are I bet he's grateful for that eye protection.
No doubt. As I said, that's the most extreme rearward ejection shown in photos I've come across on DoD web sites. Most show a more southpaw-friendly, 90-degree ejection.
I'd be interested if you had a picture of someone shooting the FG42 left-handed, since its ejection port seems well aft of the 60's.
Only shooting pics I've seen are of a "righty" -- one pic of shooting from the hip appears to show the empty case going out roughly 90 degrees; the other is fired offhand, and the case ejects forward about 45 degrees. These are on pp. 88 and 100 in Robert Bruce's German Automatic Weapons of World War II.

The FG42 ejection port looks to be about an inch more rearward than on the M60. I wouldn't classify that as "well aft" even if you do.
That's true, although 2 3/4" of that is barrel length; the Mk48 is a conventional design (feed chute fully forward of the trigger guard), and is 2" shorter than the 60 (1" discounting barrel length).
I think you're overlooking the difference in flash suppressor lengths. Put the short M240B/Mk48 suppressor on a "sixty" and it'd add to the length differential. I also think you're in error regarding Mk48 barrel length, but I don't have time to research it right now.

In any case, you're getting us hung up on the specifics of the FG42 and M60. I was not advocating either, only citing them as examples of the semi-bullpup configuration, to illustrate that it offers reduced length without some of the more serious drawbacks of the bullpup layout.
My point was simply that a conventional rifle layout, while advantageous in many respects, imposes a minimum-length constraint on the designer (barrel length plus 19-20" or so for a 7.62 NATO).
There's no disagreement on that.
If one can overcome that limitation by going to a semi-bullpup layout, the tradeoff may be worthwhile; otherwise it seems pointless to forgo some of those advantages--particularly as regards belt-fed machine guns, which (as I mentioned earlier) are ideal platforms for bullpup configuration.
How do you conclude that? To me, it looks like belt feed is pretty much incompatible with the bullpup configuration. How do you get the belt into the feed chute, without interference from the gunners face? Can you cite any examples of practical, belt-fed bullpups that have actually been built?

P.S. Although I shouldn't have taken the time, curiosity compelled me to check on lengths of the M60 and Mk48. I found the following:

Mk48 - oal: 39.75" w/ 16" bbl (I don't know if this includes flash suppressor)
www.fnhusa.com/contents/mg_mk48.htm

M60E4 - oal 38.0" w/ 19" bbl (approx 20" w/ flash suppressor)
www.usord.com/M60E4Comm_USORD.html

Even with a barrel that's 3-4 inches longer, the M60 is still two inches shorter than the Mk48.

Here's another semi-bullpup. (http://world.guns.ru/assault/as78-e.htm) The TRW Low Maintenance Rifle developed in the '60s and '70s.

http://world.guns.ru/assault/trw_lmr1.jpg

http://world.guns.ru/assault/trw_lmr2.jpg

From http://world.guns.ru/assault/as78-e.htm

34" OAL, 19.3" barrel, 8 pounds loaded.

FWIW, I don't think bullpups have to be heavier than a conventional layout. After all, you eliminate the "dead weight" of a conventional buttstock. See, E.G. http://www.bullpup22.50megs.com/index.html (popup warning) and http://www.dixieconsolidated.com/.

http://www.bullpup22.50megs.com/images/dc3.jpg

The Dixied Consolidated 10/22 stock is just an aluminum dust cover/stock that clamps to the barreled action. It's lighter than a conventional wood stock and many conventional synthetic stocks for the 10/22. If it were fabricated out of a high-tech composite or synthetic like carbon fiber or Xenoy, it would probably be right down there with the lightest synthetic stocks.

BTW, I'm thinking about building one of these with a sleeved barrel (Volquartsen THM or Green Mountain Aero) to isolate the barrel from the clamping forces of the stock. I want to see just how accurate I can make a 10/22 bullpup.

Here's another semi-bullpup. The TRW Low Maintenance Rifle developed in the '60s and '70s.
I've always thought the TRW rifle looked pretty neat, although I don't care much for the side magazine. Although I've lost touch with him, I know the guy who developed it. He also created an unusual little, full-auto "arm gun" that fired .22 Magnum ammo; the rounds fed via a metal "tape" that coiled in a plastic drum.
FWIW, I don't think bullpups have to be heavier than a conventional layout. After all, you eliminate the "dead weight" of a conventional buttstock.
I don't know of anything that says bullpups have to be heavier than conventional designs, but as a rule they typically are heavier. They also have poor balance, with most of their weight being behind the pistol grip.

I disagree that it eliminates the dead weight of a stock, because bullpups generally have even more buttstock and fore end material as a conventional rifles. For perhaps the most extreme example, compare the large stock area of the FN F2000 to the amount of material on an FAL or M16.

Also, I don't know of any military bullpup that doesn't have a long length of pull. Worse, the length of pull cannot be adjusted shorter, to accommodate individuals of smaller stature or troops wearing body armor.

Don't get me wrong. I've always been fond of the bullpup concept. In the past I've owned a Steyr AUG and a Hi-Standard Model 10B shotgun, and thoroughly enjoyed both. Nobody would be happier than I if a bullpup were to be created that is lightweight, well-balanced, fully-ambidextrous, and has optimum (preferably adjustable) length of pull.

P.S. I'm still waiting for Spartiate (or anyone else) to show me how a bullpup is compatible with belt feed...

...a pure, belt-fed LMG may be the most readily convertible of all to bullpup configuration... The RPD in particular is superbly suitable for such a project...
Are you sure, Mike? I was looking at my copy of Small Arms of the World, and according to the disassembly photo and sectional drawing, the RPD has a steel tube that houses a driving spring. This tube, somewhat similar to the M16 buffer tube, appears to extend nearly the entire length of the buttstock, which would seem to make it impossible to shorten the tail end of an RPD to convert the gun to a bullpup configuration.

I've always thought the TRW rifle looked pretty neat, although I don't care much for the side magazine. Although I've lost touch with him, I know the guy who developed it. He also created an unusual little, full-auto "arm gun" that fired .22 Magnum ammo; the rounds fed via a metal "tape" that coiled in a plastic drum.

I don't know of anything that says bullpups have to be heavier than conventional designs, but as a rule they typically are heavier. They also have poor balance, with most of their weight being behind the pistol grip.

I disagree that it eliminates the dead weight of a stock, because bullpups generally have even more buttstock and fore end material as a conventional rifles. For perhaps the most extreme example, compare the large stock area of the FN F2000 to the amount of material on an FAL or M16.

Also, I don't know of any military bullpup that doesn't have a long length of pull. Worse, the length of pull cannot be adjusted shorter, to accommodate individuals of smaller stature or troops wearing body armor.

Don't get me wrong. I've always been fond of the bullpup concept. In the past I've owned a Steyr AUG and a Hi-Standard Model 10B shotgun, and thoroughly enjoyed both. Nobody would be happier than I if a bullpup were to be created that is lightweight, well-balanced, fully-ambidextrous, and has optimum (preferably adjustable) length of pull.

P.S. I'm still waiting for Spartiate (or anyone else) to show me how a bullpup is compatible with belt feed...

The easiest way to improve the balance of a bullpup is to add an UGL... It gets a little bit heavier, but will then have much better balance than a conventional rifle/carbine with an UGL... It will also be easier to handle and carry because of the smaller length.

...He also created an unusual little, full-auto "arm gun" that fired .22 Magnum ammo; the rounds fed via a metal "tape" that coiled in a plastic drum.

I remember that! I saw a write up years (decades?) ago in a gun rag. That looked like a cool little gun.

I disagree that it eliminates the dead weight of a stock, because bullpups generally have even more buttstock and fore end material as a conventional rifles.

Good point - especially if you compare the amount of comparable materials. For example an AR built on a Cavalry Arms Mk. II polymer lower receiver/stock assembly and something like the AUG or F2000

Also, I don't know of any military bullpup that doesn't have a long length of pull. Worse, the length of pull cannot be adjusted shorter, to accommodate individuals of smaller stature or troops wearing body armor.

I agree - this is an issue. Addressing it requires a short action and ambidexterous ejection. Years ago I spend some time playing with tracing paper and a diagram of a Mini 14 barreled action and came to the conclusion that a bullpup with a pull of 13" or less would be possible if upi could address the ejection issue.

I'm still waiting for Spartiate (or anyone else) to show me how a bullpup is compatible with belt feed...

Me too. I think you'd be limited to a semi-bullpup (M60), two different versions of the same platform sharing most of the components (sort of like the experimental US caseless design that could be configured as a bullpup or as a conventional rifle) or maybe a side-mounted feed cover that would pull the belt up out of a feed box or bag. Picture an MG3 turned on its side, with a shorter butt. It would feed from the bottom. Ejection is still an issue.

EDIT: I should add "given current cartridge technology". A system pushing a caseless or case telescoped cartridge from a belt into a rising or revolving chamber from the front could shave the length of the cartridge off a semi-bullpup design like the M60. The belt would be in the same place, but the breach could be farther to the rear.

Now that I think about it, the PKM is sort of like that, because it pulls the rimmed cartridges out of the belt. A cross between an M60 and a PKM would put the belt over the pistol grip, but the breach would be behind it. Technically, that would make it a bullpup.

I agree - [length of pull] is an issue. Addressing it requires a short action and ambidexterous ejection. Years ago I spend some time playing with tracing paper and a diagram of a Mini 14 barreled action and came to the conclusion that a bullpup with a pull of 13" or less would be possible...
It's a tough -- maybe even impossible -- problem to solve, at least with the conventional, bottom-feed (box magazine) configuration. It's necessary to allow about 2.5 inches from front of the trigger to rear of the grip, 3.0-4.0 inches from grip rear to magazine front, 2.5 inches for the mag, 2.5-3.0 inches for bolt travel behind the mag, and 0.5-1.0 inch for the butt plate assembly.

It appears possible to get length of pull down to the 12-13" range typical of conventional rifles like the M16, but I sure don't see any way to make a bullpup stock adjustable for shorter pull lengths (a la the M4 carbine). I thought if perhaps a top-feed, longitudinal magazine (similar to that of the P90) could be employed, then there'd be no need for the pistol grip to be placed so far forward on the gun, which would make an adjustable length of pull possible. However, that would necessitate use of a straight magazine, and I don't know if such a mag configuration could hold much more than 20 rounds of cartridges with significant case taper.
[For belt feed] I think you'd be limited to a semi-bullpup (M60), two different versions of the same platform sharing most of the components (sort of like the experimental US caseless design that could be configured as a bullpup or as a conventional rifle) or maybe a side-mounted feed cover that would pull the belt up out of a feed box or bag.
Concur.
EDIT: I should add "given current cartridge technology".
That goes almost without saying, given that this forum is devoted primarily to 6.5 Grendel, and that none of us have the means to experiment with unconventional cartridge technologies like caseless ammo. :)

The easiest way to improve the balance of a bullpup is to add an UGL... It gets a little bit heavier, but will then have much better balance than a conventional rifle/carbine with an UGL... It will also be easier to handle and carry because of the smaller length.
Very true. Unfortunately, that characteristic of bullpups only improves weapon balance for the grenadier. The riflemen are still stuck with crappy balance.

Of course, if they made every man a grenadier... ;) :D

Very true. Unfortunately, that characteristic of bullpups only improves weapon balance for the grenadier. The riflemen are still stuck with crappy balance.

Of course, if they made every man a grenadier... ;) :D

If the rifle were made with a grenade-launcher as part of the design... 30mm instead of 40mm, it could probably be possible to make the combo much lighter than it is today...

Of course, people will start to get angry if we replace the 40mm GL with a 30mm GL, but people are always like that... People would probably get angry if we replaced 7.62 with 6.5 Grendel too... That is because we replace something they have great confidence in with something new, which may not be better in their eyes...

If the rifle were made with a grenade-launcher as part of the design... 30mm instead of 40mm, it could probably be possible to make the combo much lighter than it is today...

Of course, people will start to get angry if we replace the 40mm GL with a 30mm GL, but people are always like that... People would probably get angry if we replaced 7.62 with 6.5 Grendel too... That is because we replace something they have great confidence in with something new, which may not be better in their eyes...

The Army had been trying prototypes with a 20mm gun and the 5.56 a secondary weapon underneath for CQB. Heavy and expensive.

The Army had been trying prototypes with a 20mm gun and the 5.56 a secondary weapon underneath for CQB. Heavy and expensive.

I know... But that was the IOCW... Which I could never imagine how could be practical...

Besides, If you want to have the same payload as a 40mm, you have to increase the length of the 30mm grenade by at least 1,8 times, while the 20mm will need to be increased by at least 4 times... (based on external diametre, which will not be totally) correct

Also, the GL I thought of would not be selfloading... Then it would not only be light, it would be cheap too...

What happened to the old grenade launched from the end of the rifle barrel?

Personally, I think stand alone grenade launchers are better. Never liked combining multiple weapons in a heavier package. The South African one that holds multiple rounds in a big cylinder like a revolver/rifle seems like a good concept that could be lightened up a bit.

http://world.guns.ru/grenade/gl14-e.htm
http://world.guns.ru/grenade/milkor_mgl_fire.JPG

What happened to the old grenade launched from the end of the rifle barrel?
There are safety issues with the old type, which required use of a special blank cartridge to launch the grenade. Also with "bullet-trap" grenades, which can be fired with Ball rounds, but are not safe to use with AP or Tracer ammo. "Bullet-thru" grenades overcome these problems, but I haven't heard any reason why the US military does not adopt them.

One drawback to all rifle grenades is that you can't fire a bullet, without also firing the mounted grenade. With an UGL, the grenade is always ready to launch, but bullets can be fired separately.
Personally, I think stand alone grenade launchers are better. Never liked combining multiple weapons in a heavier package. The South African one that holds multiple rounds in a big cylinder like a revolver/rifle seems like a good concept...
The Marines apparently agree. http://www.usmc.mil/marinelink/image1.nsf/Lookup/200631024050

The Army, as usual, seems to be lagging behind. :(

What happened to the old grenade launched from the end of the rifle barrel?

Personally, I think stand alone grenade launchers are better. Never liked combining multiple weapons in a heavier package. The South African one that holds multiple rounds in a big cylinder like a revolver/rifle seems like a good concept that could be lightened up a bit.

http://world.guns.ru/grenade/gl14-e.htm
http://world.guns.ru/grenade/milkor_mgl_fire.JPG

I agree... But to improve the handling characteristics of a bullpup weapon it could be the easiest and lightest solution...

And even for a conventional weapon, it could be preferrable to make two different versions... One with integrated UGL, and one without...

As have potential solutions--ejection out the bottom or (as demonstrated to virtually unanimous acclaim in the FS2000) forward.


Very true, bottom ejection is always an option.

Please elaborate. If you're talking about the ability to perform in the AR role as well (i.e. feed from both belts and magazines) I agree that it is a challenge; but a pure, belt-fed LMG may be the most readily convertible of all to bullpup configuration (if performance in the AR role is not required/desired) for two reasons.

The LMG has to be able to use both magazines and belts. The reason for this is to allow the user to use magazines when belts run out. This may not be seen as much of a needed feature in todays' military with it's far superior logistics, but it happens in combat that your LMG/SAW runs out faster because of more sustained fire. Being able to use magazines from comrades would allow the extra "lead hose" to stay in action.
The best compromise is the semi-bullpup design along the lines of the FG42.
If it could be made to the point where magazines can be inserted from either side or a belt could be fed from either side (selector switch that is manually operated or operated by magazine or belt links), it would solve the issue of southpaws using the weapon and feeling endangered.
A quick change barrel would be a must as well.

Personally, I'm with the crowd that calls for a no belt situation where Beta magazines are used.

Do you expect me to be in the forum 24 hours per day, so as to immediately read a posting from halfway around the world? :p right back at ya.It would certainly be unreasonable to expect you to make the first counter-point to every post--but I fail to see how repeating another's observation (or your own three times, as on the RPD-bullpup issue, before another poster has had the chance to respond) advances the discussion.
Mk48 - oal: 39.75" w/ 16" bbl (I don't know if this includes flash suppressor)
www.fnhusa.com/contents/mg_mk48.htm

M60E4 - oal 38.0" w/ 19" bbl (approx 20" w/ flash suppressor)
www.usord.com/M60E4Comm_USORD.html

Even with a barrel that's 3-4 inches longer, the M60 is still two inches shorter than the Mk48.
Your Mk48 link doesn't take me anywhere, but FNH's Mk48 page (http://www.fnhusa.com/products/firearms/model.asp?fid=FNF015&gid=FNG008&mid=FNM0042) doesn't list the barrel length; nor does USORD's (http://www.usord.com/M60E4Comm_USORD.html). Wikipedia lists the Mk48's barrel length as 19.75, and it's clear from any picture of the gun (to the naked eye, verified by micrometer) that (while it's obviously impossible to find the exact location of the breech-face on screen) the barrel is much closer to half than to two-fifths the length of the gun. I'm sure that includes the flash suppressor (as is generally the case with semi- or permanent muzzle devices), but there's no way it's 3 3/4". I'm not intimately familiar with the M-60E4, but the version we squids are stuck with is variously described as 42-43" long with a 22" barrel.
In any case, you're getting us hung up on the specifics of the FG42 and M60.
Our discussion has certainly wavered between these examples on one hand and objective design principles on the other, but I've tried to stay with the latter as much as possible. Regarding the principle that a conventional weapon in 7.62 can be as short as barrel length plus 19-20", you responded,
There's no disagreement on that.
From this common ground, we part ways, with you
. . . citing the[FG42 and M60] as examples of the semi-bullpup configuration, to illustrate that it offers reduced length without some of the more serious drawbacks of the bullpup layout. while I contend, on the contrary, that a semi-bullpup layout (moving the magazine or feed chute above or beside the grip) offers the designer an extremely-narrow window in which to place the ejection port before incurring the same ambidexterity penalty as a full bullpup--a window which has still, AFAIK, not produced a demonstrably-ambidextrous 7.62, significantly shorter than barrel + 19-20". I remain "hung up on" the examples you've offered to prove your point only because they favor mine :cool:.

Mike

To me, it looks like belt feed is pretty much incompatible with the bullpup configuration.
P.S. I'm still waiting for Spartiate (or anyone else) to show me how a bullpup is compatible with belt feed...
Are you sure, Mike? I was looking at my copy of Small Arms of the World, and according to the disassembly photo and sectional drawing, the RPD has a steel tube that houses a driving spring. This tube, somewhat similar to the M16 buffer tube, appears to extend nearly the entire length of the buttstock, which would seem to make it impossible to shorten the tail end of an RPD to convert the gun to a bullpup configuration.
This feature would certainly require redesign. I tend to regard any weapon--especially one of the RPD's generation, most especially when it comes with its receiver chopped into pieces--as more of a conceptual starting point to be re-engineered along modern lines, than a ready-made kit requiring simple reassembly with minor mods. Obviously difficult-to-manufacture (belt feed mechanism) or strength-critical (bolt) components would be retained, but as with the M16/AR design, there are a variety of ways to redesign the recoil assembly without a rear spring tube:
-Spring inside receiver (SKS)
-Extension spring (Beardmore-Farquhar, IIRC?)
-Spring within tube behind piston (AK) or,
-Around piston rod (SU-16). These would require moving the spring and tube or guide rod to one side, or both, of the ejection port. I like this idea, and seeing the new Kel-Tec bullpup has given me an idea how I might actually be able to build this as a closed-bolt semi.
How do you get the belt into the feed chute, without interference from the gunners face? The RPD feeds almost vertically from belt drum to feed tray. As previously mentioned, it also has a trim feed mechanism that, even if housed within a wider, U-shaped shroud/cheekpiece to keep the gunner's face out of the links on either side, would still be no wider than an M-60's 4.8". I'd prefer Hogue Over-Molded, personally. In the real world, particularly under the stress of combat, people will make mistakes, and not deploy a weapon exactly the way it's designed. After seeing your photo of the M-60 fired left-handed, I could easily see myself (as a right-handed shooter), if forced under fire to shoot left handed, forgetting to shy rearward of the ejection port, and placing my face squarely in the path of hot, high-speed empties. I'd much prefer to take my chances with cool links advancing or ejecting at 5fps or so.
Can you cite any examples of practical, belt-fed bullpups that have actually been built? I can think of numerous examples where a knowledgeable individual could inspect a weapon or feature of a weapon, and think of how it could be done better (or has, on another weapon). As you well know, most of the design principles implemented in today's "cutting edge" weapons were well-known by WWII. Was any single feature of the Grendel cartridge beyond the grasp of handloaders in the 20s? How many WWI rifles mounted "1913" Picatinny rails? Why do so many rifles and MGs optimized for simplicity of manufacture incorporate so many elaborate parts and superfluous machining steps? The answers to most of these questions are case-specific rather than matters of general principle. The best answer I have to your question is that most nations favoring bullpup rifles prefer heavy-barrel derivatives thereof in the LMG role. I freely admit(ted in a previous post) that a GPMG feed tray is too wide for the modification I described.

Sorry to keep you waiting,
Mike

Can you cite any examples of practical, belt-fed bullpups that have actually been built?The best answer I have to your question is that most nations favoring bullpup rifles prefer heavy-barrel derivatives thereof in the LMG role.
I'll take that as a "No." :D

However, after reading your post, and upon further contemplation, it looks to me as though a belt-fed bullpup might be feasible.
It would certainly be unreasonable to expect you to make the first counter-point to every post--but I fail to see how repeating another's observation advances the discussion.
He only corrected your statement about location of the FG42 mag. I wanted to expand on that, so it seemed appropriate to restate it.
Your Mk48 link doesn't take me anywhere, but...Wikipedia lists the Mk48's barrel length as 19.75
I don't know why you can't access the link I provided. Try www.fnhusa.com/contents
or www.fnhusa.com and go from there to the Mk48 page. At the bottom, under "overall length" it shows 39.75" (16"). I read that to mean 39.75" is OAL with a 16" barrel. I figure FNHUSA is a more authoritative source than Wikipedia...
I contend...that a semi-bullpup layout (moving the magazine or feed chute above or beside the grip) offers the designer an extremely-narrow window in which to place the ejection port before incurring the same ambidexterity penalty as a full bullpup...
I agree. I have never said otherwise. My point from the beginning is only that, with barrels of the same length, a semi-bullpup offers a shorter overall length than a conventional configuration, without some of the disadvantages of a bullpup. Each configuration has both good points and bad.

It does not seem possible to design an "ideal assault rifle," because no matter which configuration is chosen, it will have some undesirable characteristics that make it less than ideal. You just have to decide which good traits are most important to you, and which bad traits you're willing to live with.

The LMG has to be able to use both magazines and belts. Most militaries seem to disagree, since the M-249 is fairly rare in incorporating that feature; even the 249 offers that "capability" in a very loose sense of the term, being highly unreliable with box mags, and FNH has discontinued the feature in the follow-on Mk46 and Mk48.

A notable exception to this general trend is Sweden. I had the pleasure of working with a highly professional naval-infantry security company there; their rifles seemed to be an even mix of AK5s (Swede FNC variant) and mag-fed Minimi Paras.
Personally, I'm with the crowd that calls for a no belt situation where Beta magazines are used. I like the idea as far as SAWs are concerned, since the capacity is the same as the belt bag, and reloading is faster. I see the advantages and disadvantages on both sides. With (as discussed numerous times on these boards) the primary limitation on ammo carry being, not weight, but the number of feeding devices that can be carried ready to hand, the primary drawback of any drum is its irregular shape when compared to either box magazines or belt boxes.
The best compromise is the semi-bullpup design along the lines of the FG42. If it could be made to the point where magazines can be inserted from either side . . .As per my discussion with Stan above, I don't see much potential in the semi-bullpup, since conventional-layout rifles have their ejection ports about as far to the rear as can be safely fired left-handed. However, I like this idea overall--magwells on either side (maybe with M-16 ejection-port-type dust covers) would allow a bottom ejecting, true bullpup to function safely and reliably from either shoulder. M-16 magwells would probably be too bulky, but a receiver configured to fire AK mags should not be too bad.
A quick change barrel would be a must as well.I concur wholeheartedly, and regard this feature as integral to any design, quite apart from any requirement or desire to change barrels in the field. In this day and age in general--and with the simple, compact fixed-headspace AR breech in particular--it is ludicrous for this basic component (a part with more varieties available than almost any other) not to interchange readily without punches, presses, vises, and wrenches. Some have pointed to the added bulk and weight of changing handles as undesirable on non-LMG barrels, and I agree--but there's no reason a simple, separate spanner (like a 1911 bushing wrench) couldn't substitute where AR, PDW, and DMR barrels are concerned.

Take care,
Mike

Stan,
Seeing our posts sliding toward an exchange of snipes and one-upmanship as well as ideas, I tried to moderate the tone of my last post, only to find you outdid me in courtesy--touche'. ;)
I'll take that as a "No." :D

However, after reading your post, and upon further contemplation, it looks to me as though a belt-fed bullpup might be feasible.Such a concession from a man of your acerbic wit is a compliment indeed, for which I thank you--of course, we'll only really know until and unless I start cutting and folding steel. :D
I don't know why you can't access the link I provided. Try www.fnhusa.com/contents
or www.fnhusa.com and go from there to the Mk48 page. At the bottom, under "overall length" it shows 39.75" (16"). I read that to mean 39.75" is OAL with a 16" barrel. I figure FNHUSA is a more authoritative source than Wikipedia... I followed the fnhusa link, to "Machine Guns", "M-240 Series", "Mk48 Mod0", and still see no reference to barrel length, nor the number 16 anywhere--maybe it's on the super-triple-classified page available only to the Secret Brotherhood of Gunwriters. I'm afraid we'll have to agree to disagree on this one--the 48 looks to be as perfect a real-world implementation of the aforementioned ideal conventional layout formula as I've ever seen, and (unless it has a ridiculously-long length of pull) I can't see any conceivable way for it to be 23.75" behind the breech.
It does not seem possible to design an "ideal assault rifle," because no matter which configuration is chosen, it will have some undesirable characteristics that make it less than ideal. You just have to decide which good traits are most important to you, and which bad traits you're willing to live with.
I certainly agree that it's impossible to please all of the people all of the time, but see numerous consumer products and military hardware alike that contain no inherently "bad" traits, and incorporate enough desirable features to satisfy the majority of rational, realistic customers. It seems as though the state of small-arms development has reached a point where the attainment of such a goal can be reached through synthesis rather than earth-shattering innovation.

In some cases, this is as much a matter of overcoming prejudices and (much as I hate the word) paradigms as of actual material improvements. I am referring specifically to this assessment:
Weight & Balance:
Conventional (Lightest/Good) -- Semi-bullpup (Intermediate/Fair) -- Bullpup (Heaviest/Poor)
A wingshooting gun should have a "between the hands" or forward balance to swing through a lead, and a bolt, falling-block, or lever gun (and numerous semi-autos, due to the designer's choice of op-rod or cocking-handle location) is held in the weak hand while being cycled with the strong. Consequently, a gun that balances this way feels "right" or "good" to most people on first inspection. In practice, an assault rifle--or home-defense longarm, brush-country deer rifle, dangerous-game or rabbit/squirrel gun--in short, any weapon meant to be held at the ready, or rapidly deployed from a tac-sling position, with one hand sweeping aside briars and branches, hauling oneself over minor obstacles, opening doors, cycling the weapon, performing countless other tasks, or injured, is a "hand and a half" weapon that should balance in the strong hand (or be light enough not to matter) without fatigue for an extended period of time. Even if a bullpup's balance starts slightly aft, the tactical operator or amateur enthusiast alike will quickly accessorize any rail-configured gun until it balances in the middle or slightly forward, even without a UGL.

Take care,
Mike

Stan,
Seeing our posts sliding toward an exchange of snipes and one-upmanship as well as ideas, I tried to moderate the tone of my last post, only to find you outdid me in courtesy--touche'.
I have my moments. :D
Such a concession from a man of your acerbic wit is a compliment indeed, for which I thank you--of course, we'll only really know until and unless I start cutting and folding steel.
I'll admit that I can be hard to convince, but when presented with sufficient facts or logical argument, I have no problem changing my stand on a subject.

I sincerely hope that you do tackle the project, as I'd find a belt-fed bullpup very interesting.
I followed the fnhusa link, to "Machine Guns", "M-240 Series", "Mk48 Mod0", and still see no reference to barrel length, nor the number 16 anywhere--maybe it's on the super-triple-classified page available only to the Secret Brotherhood of Gunwriters.
Oh, you're not a member of the brotherhood? No wonder you couldn't access the page. ;)

Actually, I just tried it (the link I originally posted, that is), only to find that I couldn't access it, either. So I then took the route that I suggested to you, and began on the FNHUSA main page...where I got a bit of a SURPRISE! With incredibly inconvenient timing for this discussion, FNHUSA revamped their web site sometime after I posted that link on 3 January, and before you attempted to access it. :eek: Every page that I looked at today is different than it was 12 days ago. There is no way I can now prove that the Mk48 page showed 16" as barrel length. :(
I certainly agree that it's impossible to please all of the people all of the time, but see numerous consumer products and military hardware alike that contain no inherently "bad" traits, and incorporate enough desirable features to satisfy the majority of rational, realistic customers.
You're taking my use of "bad" too literally. I meant it as a synonym for "undesirable"; one such aspect of bullpups is the length of pull, which is longer than optimum for most people, and cannot be adjusted shorter for smaller individuals or troops wearing body armor.
In some cases, this is as much a matter of overcoming prejudices and (much as I hate the word) paradigms as of actual material improvements.
Concur.
...any weapon meant to be held at the ready, or rapidly deployed from a tac-sling position, with one hand sweeping aside briars and branches, hauling oneself over minor obstacles, opening doors, cycling the weapon, performing countless other tasks, or injured, is a "hand and a half" weapon that should balance in the strong hand (or be light enough not to matter) without fatigue for an extended period of time.
Sounds logical.
Even if a bullpup's balance starts slightly aft, the tactical operator or amateur enthusiast alike will quickly accessorize any rail-configured gun until it balances in the middle or slightly forward, even without a UGL.
Not having tried it with any of the bullpups I've owned (the rail gadget fad came too late for me to adopt it), I can't verify how much forward weight would shift with typical accessories, but balance should certainly benefit.

Judging from pictures on guns.ru, I believe the Mk48mod0 has a 18" barrel, as it looks very similar in length to the 18" 5.56 Minimi.

Mk48mod0 (http://world.guns.ru/machine/mg38-e.htm)
5.56 minimi/M249 (http://world.guns.ru/machine/mg17-e.htm)

About a beltfed bullpup with downwards ejection, one problem which will arise is where the hot brass is going... From experience, I know how hot MG-brass against bare arms feel...

About semi-bullpup ejection, I believe this is only a problem for certain designs... The G-3 normally ejects brass 45degrees forwards...

Also, about length of pull, I dont know exactly, as I have very little experience with bullpups, but I suspect the length of pull to be less of an issue there than in an orthodox gun...

I have at least experienced one thing: I never have problems reaching the pistolgrip on the G3... But getting a good grip on the fore-end is more difficult... With a bullpup, you would not have those problems, and neither would you with a semi-bullpup... So, one possibility could be to move the magazine/pistolgrip a little more forwards than what would be preferrable on an orthodox rifle (you can do that with an adjustable stock)...

FNMI's webpage lists the barrel length of the new Mk 48 Mod 1 as 19.75".

http://www.fnmfg.com/products/m249fam/mk48mod1.htm

About semi-bullpup ejection, I believe this is only a problem for certain designs... The G-3 normally ejects brass 45degrees forwards...
Yes, it would depend on the particular design. For an extreme example, one need only look at the SAR-21, which has right-side only ejection. Since it is a true bullpup, yet appears to be safe for left-handed shooters, then there is no obvious reason that a semi-bullpup could not also have a safe-for-lefties ejection pattern. That's why I was trying to get Spartiate to part with his fixation on the ejection pattern in that one M60 picture. Instead of that photo, I guess I should've posted the picture below, which shows empties being ejected at approx 90 degrees. :D
Also, about length of pull, I dont know exactly, as I have very little experience with bullpups, but I suspect the length of pull to be less of an issue there than in an orthodox gun...
I just don't see why this would possibly be so. Can you offer more basis for this idea than just suspicion?
I have at least experienced one thing: I never have problems reaching the pistolgrip on the G3... But getting a good grip on the fore-end is more difficult... With a bullpup, you would not have those problems, and neither would you with a semi-bullpup... So, one possibility could be to move the magazine/pistolgrip a little more forwards than what would be preferrable on an orthodox rifle (you can do that with an adjustable stock)...
Moving the grip forward would increase length of pull. That doesn't seem very desirable for a configuration where pull length is already very long to begin with. :confused:

I just don't see why this would possibly be so. Can you offer more basis for this idea than just suspicion?

Moving the grip forward would increase length of pull. That doesn't seem very desirable for a configuration where pull length is already very long to begin with. :confused:

I shoot righthanded... In the standing position, I have no problem shooting the G-3, as my left hand easily can reach the fore-end of the rifle... In the prone position however, I have problems reaching the fore-end, and end up with a grip around the front of the magwell... It is okay to shoot with support, but very heavy to shoot without...

If I could move my left hand closer to my body (because there is no magwell in the way), I dont think I would have any problems with my right hand being a bit further from my body...

Also, about length of pull, I dont know exactly, as I have very little experience with bullpups, but I suspect the length of pull to be less of an issue there than in an orthodox gun... Thank you for bringing up this important aspect of bullpup design--a belief I share, but forgot to mention when discussing bullpup balance with Stan.
I just don't see why this would possibly be so. Can you offer more basis for this idea than just suspicion? "Length of Pull" is certainly the standard term, but a bit misleading, since it seems to imply an issue with trigger reach. I'm only 5'10", but my fully-extended arm measures 24" from shoulder to the pad of an index figure curled as though touching a trigger. Of course, no one would never hold a rifle at arm's length, unless forced to do so for disciplinary purposes by a drill instructor--a memory (not too painful, I hope ;)) you two vets might share, and find illuminating for the discussion at hand. The sensation of discomfort in both cases (varying only in degree) is the body's perception of a moment--the weight of a rifle (acting downward from its balance point) multiplied by that point's distance from the shoulder muscles supporting the weight. When I shoot a rifle with an excessive LOP (like my FAL with a recoil pad, particularly before I exchanged a medium-heavy 20" barrel for a light 17-incher), its forward balance tends to rotate downward in my firing hand, creating a feeling that the hand is "too far" from my shoulder; it doesn't help that my support hand, when resting on my chest, is also an inch or so farther forward than feels natural because the magazine's in the way. On the other hand, my bullpup Ithaca 37, which has a heavy machined-steel receiver, and consequently a pronounced rearward balance (it would probably be more centered with the full-length tube magazine topped up) tends to rotate into my shoulder when gripped in one hand. It won't win any skeet matches, but I can carry it that way without discomfort while opening doors, sweeping aside obstacles, etc.--a boast I could never make regarding my "better balanced" over/under. In practice, therefore, a these two bullpup "disadvantages" (really just differences from long-held norms) tend to mitigate each other's effects--leaving the designer to solve the real problems of trigger feel and ejection. Speaking of which:
For an extreme example, one need only look at the SAR-21, which has right-side only ejection. Since it is a true bullpup, yet appears to be safe for left-handed shooters . . . I'd love to hear how they do it!

Take care,
Mike

Also, about length of pull, I dont know exactly, as I have very little experience with bullpups, but I suspect the length of pull to be less of an issue there than in an orthodox gun...Thank you for bringing up this important aspect of bullpup design--a belief I share...
Since length of pull has been an issue mainly in regard to interface with body armor, I just don't see how this aspect would be any different for bullpups than for conventional rifles.
"Length of Pull" is certainly the standard term, but a bit misleading, since it seems to imply an issue with trigger reach.
Since the term is a measurement of trigger reach, how can it be misleading? :confused:
Of course, no one would never hold a rifle at arm's length, unless forced to do so for disciplinary purposes by a drill instructor--a memory (not too painful, I hope) you two vets might share...
I think that memory was blocked by my subconscious. ;)
When I shoot a rifle with an excessive LOP (like my FAL with a recoil pad, particularly before I exchanged a medium-heavy 20" barrel for a light 17-incher), its forward balance tends to rotate downward in my firing hand, creating a feeling that the hand is "too far" from my shoulder; it doesn't help that my support hand, when resting on my chest, is also an inch or so farther forward than feels natural because the magazine's in the way.
As a counterpoint, I can offer the examples of the M1A and AR15A2 that I once owned. The AR15A2 was over 1 pound lighter, with a length of pull approx 1 inch longer, than the M1A with its M14A1 stock. At 6 feet tall, my arms are not short, but I found the fit, feel, and handling of the M1A much superior to the AR15A2. This was despite the heavier overall weight, the greater weight concentration forward of the pistol grip, and the longer distance from the grip to the front of the magazine.

I regret that I don't have a good recollection on this aspect of the bullpups I've owned.
On the other hand, my bullpup Ithaca 37, which has a heavy machined-steel receiver, and consequently a pronounced rearward balance tends to rotate into my shoulder when gripped in one hand. It won't win any skeet matches, but I can carry it that way without discomfort while opening doors, sweeping aside obstacles, etc.--a boast I could never make regarding my "better balanced" over/under.
Yes, that is definitely a good point in favor of bullpups, although it doesn't address the matter of body armor interface.
In practice, therefore, a these two bullpup "disadvantages" (really just differences from long-held norms) tend to mitigate each other's effects--leaving the designer to solve the real problems of trigger feel and ejection. Speaking of which:
I'd love to hear how they do it [with the SAR-21]!
Very simply. Molded into the synthetic stock, to the rear of the ejection port, is a case deflector similar to that on post-M16A1 variants. The ejected case gets bounced forward off the deflector.

Since the term ["length of pull"] is a measurement of trigger reach, how can it be misleading? :confused:.
Not deliberately or inherently misleading, just not very descriptive of the ergonomic issues involved. The dimension is a measure of trigger reach, but no one but a midget would actually have a problem reaching the trigger of any existing rifle, bullpup or otherwise. "Excessive LOP" is a sensation of over-extending the (still quite bent) arm while holding a particular gun.
As a counterpoint, I can offer the examples of the M1A and AR15A2 that I once owned. The AR15A2 was over 1 pound lighter, with a length of pull approx 1 inch longer, than the M1A with its M14A1 stock. At 6 feet tall, my arms are not short, but I found the fit, feel, and handling of the M1A much superior to the AR15A2. This was despite the heavier overall weight, the greater weight concentration forward of the pistol grip, and the longer distance from the grip to the front of the magazine.Really? The 14 is definitely heavier, but (as issued) pencil-barreled, with most of its weight in a massive forged receiver and barn-beam stock (vs. a heavy barrel, minimal-dimensioned unstressed aluminum receiver, and hollow plastic stock for the A2 AR). Was your M1A an HB variant? I guess a loaded magazine would make the difference.
Yes, that is definitely a good point in favor of bullpups, although it doesn't address the matter of body armor interface.I know body armor (and web gear) aggravate excessive LOP by adding 1/2-1" of pull, but I'm not sure if you mean something more by "body armor interface".
Very simply. Molded into the synthetic stock, to the rear of the ejection port, is a case deflector similar to that on post-M16A1 variants. The ejected case gets bounced forward off the deflector.I'd be interested in shooting one to try it out, since I can't work out the physics in my head. An M-16's deflector works because it's between a lefty's face (behind the ejection port) and the case. It seems as though a SAR-21 case mouth would be hitting the shooter's cheek or ear while, or before, the rim hit the deflector. If such a simple solution does work, though, it would seem to be more popular, and obviate not only the intense debate about this most-severe drawback of bullpups, but also elaborate solutions like the FS2000's forward ejection.

I'll probably never get a shot, though. One would think an entrepreneurial nation like Singapore would market its robust line of small arms aggressively, but they hardly seem available at all. I still regret missing out on the small shipment of Ultimax kits available a year or two ago.

Take care,
Mike

I found the fit, feel, and handling of the M1A much superior to the AR15A2. This was despite the heavier overall weight, the greater weight concentration forward of the pistol grip, and the longer distance from the grip to the front of the magazine.Really? The 14 is definitely heavier, but (as issued) pencil-barreled, with most of its weight in a massive forged receiver and barn-beam stock (vs. a heavy barrel, minimal-dimensioned unstressed aluminum receiver, and hollow plastic stock for the A2 AR). Was your M1A an HB variant? I guess a loaded magazine would make the difference.
Yup, really...I wouldn't lie to you. :D It's true the AR15A2/M16A2 has a lighter receiver, but the barrel is only heavy for about 6 inches at the front end; that portion of the barrel hidden by the front handguard is, iirc, smaller -- about the same diameter as the M16A1. Also, the M14/M1A has a barrel 2 inches longer (mine was not a HB), and a flash suppressor that's also about 2 inches longer. Figure in the longer overall length, and the fact that the steel receiver is entirely forward of the pistol grip, and it can't help but have more weight ahead of the pistol grip. (See attached photo) Naturally, loaded mags would exacerbate the difference.
I know body armor (and web gear) aggravate excessive LOP by adding 1/2-1" of pull, but I'm not sure if you mean something more by "body armor interface".
That's what I meant.
I'd be interested in shooting one to try it out, since I can't work out the physics in my head. An M-16's deflector works because it's between a lefty's face (behind the ejection port) and the case. It seems as though a SAR-21 case mouth would be hitting the shooter's cheek or ear while, or before, the rim hit the deflector.
Okay, now you're making me question my memory. It was 6-7 years ago that I got the chance to shoot a SAR-21, so it's quite possible that my recall is faulty insofar as the mechanics are concerned. I cannot now say for certain that the ejected cases are bounced forward off the case deflector, or if the ejector itself is somehow designed to throw the cases forward. All I can now report for sure is that I fired a SAR-21 from the left shoulder, without having any cases ejected into my face. :cool:
I still regret missing out on the small shipment of Ultimax kits available a year or two ago.
I have a friend who knows somebody who has an Ultimax. He says it's a really sweet-shooting "sheen" gun. I'm hoping that maybe one of these years I'll be lucky enough to get to get some trigger time on it myself. :)

Anyone thought about Magpuls new Masada rifle in 6.5. The bolt already exists (7.62x39 ?)and just put thier barrel nut and piston assembly on a 6.5 barrel and install. Or even a redesign of the upper for belt feed for an LMG. Use plastic links .Same material other non metal parts are made of ? Same could apply to other manufacturers weapons .Scar , HK . Just a thought .

There is a thread dedicated specifically to the Masada and talk of Grendel options somewhere else on this forum.

Actually, there is another way of making a semi-bullpup...

The PKM is a good example of that...

It feeds from the feed-tray which is placed above the chamber, from where the rounds are pulled out backwards to a position where the bolt can pick it up and insert it into the chamber...

It could be interesting to see this done with an assault-rifle, even though I fear it may be a bit bulky... A top-fed auto-rifle in this configuration might actually work quite well, even though it may not use the same magazines as a "old-fashioned" assaultrifle...

I guess I'll stick these links to Kel-Tec's RFB here. Very interesting development. Judging from the diagram of the trigger, however, I don't know if/how well it would lend itself to select fire.

http://www.kel-tec.com/news.html (Kel-Tec News, including the RFB)

http://www.kel-tec.com/images/downloads/RFB_Flyer_SHOT_2007_web.pdf (.pdf brochure - 2 MB)

http://www.kel-tec.com/download.html (video - Looks like it kicks pretty hard. 6.5 Grendel - or even .260 Remington or .243 - anyone?)

Assuming it offers comparable accuracy and reliability (a big assumption at this point) it would offer a more compact alternative to SLRs like the FAL, CETME/G3 and FAL...

Actually, there is another way of making a semi-bullpup...

The PKM is a good example of that...

It feeds from the feed-tray which is placed above the chamber, from where the rounds are pulled out backwards to a position where the bolt can pick it up and insert it into the chamber...

It could be interesting to see this done with an assault-rifle, even though I fear it may be a bit bulky... A top-fed auto-rifle in this configuration might actually work quite well, even though it may not use the same magazines as a "old-fashioned" assaultrifle...

Agree :) See post #520 above ;)

Now that I think about it, the PKM is sort of like that, because it pulls the rimmed cartridges out of the belt. A cross between an M60 and a PKM would put the belt over the pistol grip, but the breach would be behind it. Technically, that would make it a bullpup.

An AR converted to fire from p90 magazines. I wonder if its possible to feed larger ammo into a top feed 90 degree rotation magazines like the p90 and not have it protrude off the sides too much.


http://photos1.blogger.com/img/227/6119/640/ar57prototype2.jpg

I played with different angles to slim it down some. I think somewhere between 45 and 60 degrees worked because it kept the ammo capacity high, while slimming it down some so the gun didn't have the profile of a two by four lying flat.

I kindof abandoned my project because I have no time or money to prototype the damn thing. Initial goal was to do what the Masada does (very close internally too) in using existing AR components, but flip it into an inverted bullpup config like a P90. Sigh...too bad I just don't have the time or money or the desire to play footsie with the BATF when they want thier cut for manufacturing firearms.

I wonder if its possible to feed larger ammo into a top feed 90 degree rotation magazines like the p90 and not have it protrude off the sides too much.
I suppose that would depend on how much you'd consider to be "too much." :D

I gave some thought to this configuration awhile back. One question arose: Since the 5.7 cartridge case has almost no taper, it is well suited for use in such a large-capacity, straight magazine. Would it work with rounds (such as 5.56 NATO, 7.62 NATO, 6.5 Grendel) that have significant case taper?

The original straight mag made for the prototype AR15 had a capacity of 25 rounds, and the production mag capacity was cut to 20 rounds. Higher capacity mags have all been curved. If a straight mag must be limited to 20-25 rounds for reliable feeding, that'd seem to make the P90-type longitudinal mag a bit pointless, no?

From what I can tell the 5.7mm has a similar profile to the 6.5mm Grendel, of course I dont have either one on hand to comapre either, but I think the way the p90 mag is designed the rounds stay straight. I could be wrong of course.

Why not have the magazine load from the side and lay flat against the weapon like the p90 magazines with the 90 twist, this would allow faster magazine changes than reaching under the shooting arm, yet still keep the height of the weapon at a reasonable level. The height of your previous designs bother me just a bit, comfotably speaking, I dont like alot of height between my sights and my cheekweld.

My perfect Assault rifle would be bullpup, fed from the right side with p90 style mags, have an OAL of around 22 inches, a height of no more than 6 inches loaded with a width of no more than 4 inches at the magazine. It would have a top mounted "full length" rail starting @ 8 inches from the buttplate going forward to the 18" mark, it would have 3 6" rails at the 3,6, and 9 o'clock positions starting at the 12" mark from the buttstock, I also really like the DuoStock stock design.

That would be really, really awkward to change magazines quickly.

I disagree but I dont see how I can explain it to you very easily.

Ok, so you want it to feed from p90 style magazines or p90 size magazines? If most people are right handed, then how are you going to reload it quickly without taking your right hand off the grip? That's kind of how the AK series charging handle is on the right, when it should be on the left because the majority of people of earth are right handed. Although if you put the magazine of the left side in your design, then you wouldn't be able to shoulder it properly. Please explain the best you can, thats what this long-winded thread is for!

Using a p90 style magazine that should not be more than 3/4" wide. Even use the same style locking mechanisim as the p90 (slide "bottom" of magazine into pocket, then press flat to lock). To load a mag on the right side of the weapon you would lower the weapon to point at the ground, across your body, holding magazine in the left hand with the "bottom" away from your thumb, insert unto pocket then press flat.

If the magazine release were located near the thumb of the firing hand you could release and drop the magazine just by tilting the weapon slightly to the right. while readying a new mag with the left.

If a left hand feed were more desired the procedure would be the exact opposite. If the weapon was made modularly you could have a unit armorer switch between left and right feed depending on the user.

Ok that makes some more sense, but now I can't decide if it would be better loaded left or right side... I guess it would be smart to let the armorer switch it like you said. Great idea, its always good to have innovative and new thoughts!

Some company converted a ar-15 to 5.7mm that feeds from the P90 mags. Basically the mag on top of the forend and feeds downwards into the chamber. If someone can find a pic it would be great

Look earlier in the thread. I proposed one that instead of being inserted from the top, or using a side mounted design like you suggested, the magazine slips in from the side and is mounted on top. If you were a righty, you would insert it similar to how you described, except it would slip out the other side of the gun during reload OR you could pull it towards you with a magpul type lanyard before inserting the new magazine. There is an illustration somewhere earlier in this thread. Basically the sights would be mounted on a roll bar that acts as part of the frame around the magazine.

Check about Page 10 of this thread for some concept cutaway's of the mag and weapon I was designing at the time. It explains it better than I can...not to mention gives an idea of scale, compared to an M4 for fun.

the reason I suggested a feed from the side is to reduce profile, the issue I see with fitting a 2.5" wide .75-1" thick magazine(approx size of 5.56 magazine on top of the weapon is the width of your magazine is now the width of your rifle. with the magazine being mounted along the side of the weapon you now have a 2.5" minimum high weapon, which is much more comfortable IMHO.

on a side note:
I had an epiphany last night that would allow a bullpup rifle to only require about 150% of the cartridge length between the rearmost part of the magazine and the end of the buttstock, as well as removing any issues with trigger pull. To use the P90 for example you could increase the barrel length about 3" without increasing the overall external dimensions.

Well don't leave us in the dark, tell us about it.

Also, I had an epiphany last night, if your magazine feeds from the right side, then where is it going to eject? Into the guys face or what?

In regards to my bullpup epiphany, I want to keep it a bit quiet for a bit, I'd like to work it out a bit more to make sure it would work the way I want, without spreading something all over a public forum. I don't expect to make any money off the idea but I would rather not just let some random company use my idea. I do have some standards :p. The funny thing is, I wasn't even thinking about firearms, I was thinking about an engine.

as for the round ejection for my idea, thats simple, Eject it straight down, heck send the stuff out the front of the rifle, ejection direction is a matter of having a clear hole and setting up the ejector.

as for the round ejection for my idea, thats simple, Eject it straight down, heck send the stuff out the front of the rifle, ejection direction is a matter of having a clear hole and setting up the ejector.

They have developed forward ejection for a reason despite it being somewhat complex, because downward ejection doesnt work!!! especially when you are firing prone where you can back up the ejection port with rounds or even worse dirt and crud. Besides the P90 do you see any other rifle type weapons with downward ejection

I guess I can leave you alone to figure out your bullpup... for a while :D
However, I agree with Vicious, downward ejection is not very smart, although the new Keltec RFB has an innovative bolt system that kicks the cases out the front of the weapon.

Besides the P90 do you see any other rifle type weapons with downward ejection

FN MAG/M240 GPMG

My concern with downward ejection in a bullpup (with a top or side mounted helical or P90 style magazine) would be hot brass burning the operator's forearm.

Well, I worked out the ejection and the trigger group as well as the Safe/fire and Semi/Auto aspects.

For ejection it would actually eject forwards from beneath the barrel.

On a side note, what does everyone think of two seperate selectors, one for Safe/Fire and one for Semi/auto. The way the trigger interacts with the hammer would have required something alot more complicated to have a single Safe/Semi/Auto switch.

The Safe/Semi switch would be actuated by the trigger finger, and the Semi/Auto would be actuated by the thumb of the firing hand.


One more thing, does anyone have a diagram how the P90 feed system works?

FN MAG/M240 GPMG

My concern with downward ejection in a bullpup (with a top or side mounted helical or P90 style magazine) would be hot brass burning the operator's forearm.

thats why I said rifle type weapons not MGs. I dont see a problem with weapons like the m240 because the gun is usually raised up on a bipod and the casings have space to pile up, but like you said hot brass and the fact that the weapon is alot closer to the ground can cause some problems

Vicious, other downward-eject, rifle-type weapons that come to mind are the Calico 9mm SMG and carbine. Calico also had a prototype 12-ga shotgun that was shown to me when I visited the company years ago.

I don't see downward ejection in a rifle as having the problems some here think it has.

Burning the shooter's arm? Have there been any complaints about this happening with the P90 or Calico?

Piling up/clogging the ejection port when firing prone? I doubt it is likely with a bullpup, although with a conventional configuration (like the M240 machine gun, which has the ejection port ahead of the trigger guard), it could certainly happen if the ejection port were rested on a sand bag, wall, etc. That problem is easily neutralized via training.

No, the primary issue with downward ejection in bullpup rifles is that nearly all bullpups made to date are bottom-fed, with a box magazine which occupies the region of the weapon where the ejection port would need to be located. If the ejection port were to be put behind the magazine, then length of pull becomes so great that only someone with the long arms of a gorilla could reach the trigger.

One more thing, does anyone have a diagram how the P90 feed system works?
This question comes a day late. I just threw out a line drawing that might've been what you are looking for.

However, the P90 feed system is basically the same as other mag-fed guns. The mag spring pushes the cartridges rearward, where the "top" round is rotated 90 degrees by a camming surface molded into the magazine, and positioned into the mag lips. The bolt then strips the round from the mag, and pushes it into the chamber.

Hey Stan, what is your opinion of the "side loading ammo casette" Idea I had. Just curious, and would like some input on it. Its a P90 style mag, but instead of going butt forward and slapping it down (and having to reverse the process to pull it) you slap it in from the side (again, butt forward first) but when you eject, the magazine you can either pull it towards you for mag retention, or push it out the other side if you are in a hurry (while you are in the process of inserting the new mag; kinda like how the G11 was supposed to push any unburnt residue or unfired cartridges out of the chamber by pushing the fresh round into the chamber). I also intended it to be able to take AR pattern, or AK pattern magazines, "Bren" style in a pinch, by adding a mag latch and cutout in the top rail over the feed port. It obscures the main sights, but P90 style offset irons would be cut into the rail for emergencies and in an emergency like that, chances are, you arn't going to be "sharp shooting" anyway.

Cool, your idea seems like it could work. I like the idea of being able to top load AK mags. If the bullpup were chambered for 6.5 Grendel, it'd have the correct bolt face for 7.62x39, giving the potential for using battlefield pickup mags with only a barrel change.

One thing still bothers me about straight, P90-type mags and cartridges with tapered cases:
Are high-capacity (> 20 rds) mags feasible?

Thats why my initial design was based on the grendel. Carry a spare barrel in the indiginous caliber...

I think the P90 style mag can be made to work with larger rounds and tapered rounds, but instead of a full 90 degree turn, you have to get the rounds to stack more like .22s in a semi auto pistol. Because of the rim, you have to angle them about 15 to 30 degrees or the rims lock on each other. Look at a Ruger Mk1 pistol for an example. This not only avoids rim locking, but makes it possible to stack more tapered cartridges like the 7.62x39. With the grendel, its not as pronounced a taper, so if you design the guts of the mag right, with guides for the shoulders and tip of the round as well as the main barrel of the case, it should work. The 5.7x28 has a similar, small taper to the case IIRC.

The standard mags I designed were 30 or 40 rounders. For High volume of fire apps, like an IAR, you would just use a beta mag and sight over the flat of the mag. Either that, or your co-gunner/loader would be in charge of swapping the sticks durring bursts. With a translucent mag, he could watch the round count, and then in between bursts, swap the mag. This would also allow for cooling, minimizing the need for swapping out barrels. For barrel swapping I was thinking of something similar to the "Masada" with the adjustable front sight mounted directly to the barrel, so that you could preset the sights on each barrel, therby maintaining zero during barrel swaps. Either that or mount a rail on each barrel and have it mounted with its own EOtech HUD.

Soooo many possibilities
Maybe its time to restart my design progress.

Oh, another added bennifit of the top mounted mag...you can watch your round count without having to move your rifle from firing position, nor do you have to take your strong hand off the grip for mag changes if I design this puppy right. I was looking at trying to keep it so you can keep full or Partial cheek weld during a mag change.

Okay, enough of my ranting, I guess its time to revamp the design again.

Perhaps a little off topic but does anyone have or know where I can get a blueprint or contour drawing of the 16" barrel for an M-4 Carbine? I would like to make a 6.5 Grendel with this form but haven't been able to find a barrel contour drawing. Dimensions, please... Thanks in advance.

Hi!

My dream rifle for my dreamland's army is a XM8 rifle with combined a balanced action dual gas-piston system like in the Kalashnikov AK-107 and AK-108 assault rifle:
http://modernfirearms.net/assault/balanced_action.gif
[find out in this page how this stuff works...] (http://modernfirearms.net/assault/as07-e.htm)
I think the 6.5 Grendel is a perfect cartridge for assault rifles but the only drawback is the large recoil (http://en.wikipedia.org/wiki/Recoil) that it causes when fired. The 6.5 Grendel has a significantly larger recoil than in the AK-107 and AK-108, so the perfect XM8 based weapon needs a massive balanced action dual gas-piston system to negligate this effect not only in the two (AN–94 "Abakan") of three (M16A2) burst mode but in the automatic mode too.

My search for the ideal military ammo led to the following idea of a cartridge system:

The CARTRIDGE:

-The case is similar to the Russian SP-5 and SP-6 subsonic assault rifle ammunition, the 7.62x39 necked up to 9 mm.
http://2.bp.blogspot.com/_qflUzEZHwes/S1wz0NI3syI/AAAAAAAAAD8/G6xJnwBY8oo/s1600-h/9x39.JPG
-This case is not very bottle-shaped but has straight walls, which led to excellent accuracy.
-In this case with a SABOT we can put a lot of type of bullets from 6.5 mm calibre 9.3 g (143 grain) Lapua bullet for long range sniping down to a 4.7 mm calibre 3.2 g (49 grain) bullet from the 4.73x33 for G11 (the last one is my personal favorite for average soldiers) been made with spoon tip bullets).
-Even it is possible the case and the SABOT must be made from biodegradable very light plastic, fed by lacquering that prevents it from degradation in the storage period, and let it degrade after it shot from a rifle.
-Of course the loading can be varied from 1.5g (23 grain) to 2.07g (32 grain) depending on the purpose of the cartridge.
-Without a SABOT a 9 mm Beowulf-style subsonic round can be put into the case like in the original Russian SP-5 and SP-6 rounds.


The RIFLE SYSTEM:
-A 9 mm calibre rifle system must be made for this cartridge. With this calibre we won't have any capillarity problems and with the sabot type rounds the burning will be very effective and the burning gases will push the saboted bullet out of the barrel with greater force exerted to it. Possibly the sabots could be designed so that they help keep the rifle's bore clean.
-The base is a common receiver on which several parts can be installed creating a wide variety of weapons from short barreled CQB weapons to sniper rifle.
-The common receiver must be based on today's most advanced assault rifles: the FN SCAR or the HK 416/417.
-It must be combined a balanced action dual gas-piston system like in the Kalashnikov AK-107 and AK-108 assault rifles.
http://1.bp.blogspot.com/_qflUzEZHwes/S1w4p3j32GI/AAAAAAAAAEU/BD9fpNSw99g/s1600-h/balanced_action.gif
-The magazine of the rifle system must be available to accept classic 7.62x39 rounds and let it fire from the rifle with only a barrel change needed. I think this last feature is very necessary because our troops often makes operations in areas where lots of AK-s and M43 7.62 (as the world most common) cartridge can be found.
-Other solution is an interchangeable magazine receiver that every soldier can take with himself with an 7.62 barrel, this allows the use of the original AK47 mags and bullets.
-This system allows to shoot a lot of type of bullets from the same cartridges from the low recoil micro-calibers (without any capillarity problems!) to the heavy sniping and subsonic rounds creating a one-caliber system.
-The SABOT system reduces the importance of the barrel length.

You can see a summary graphics here: (http://1.bp.blogspot.com/_qflUzEZHwes/S1w2cG5aJUI/AAAAAAAAAEM/vrfJ5vIT6-E/s1600-h/Unified+Rifle+System+URS.jpg)
http://1.bp.blogspot.com/_qflUzEZHwes/S1w2cG5aJUI/AAAAAAAAAEM/vrfJ5vIT6-E/s1600-h/Unified+Rifle+System+URS.jpg

Base idea came from:
-http://www.angelfire.com/art/enchanter/bullet.html
-http://guns.connect.fi/gow/2030.html


So what do you think?
http://arjunakunti.blogspot.com/