lack of recoil-operated semi rifles?... why?

[Slamfire]

As far as bolt hold opens go, if the Soviets (AK47), German Army (G3), and Brits (L1A1) had wanted a BHO they would have designed one in. The Brits had to delete the automatic BHO on the L1A1 because they didn't want it. BHOs are not without demerits, they allow more garbage into the gun and are yet one more control that needs to be trained on.

Whereas the Americans have a tradition of BHO devices, primarily there, in my opinion, so they could play the XTC game, the British Lee Enfield never had one, so there was not any core advocacy within the requirements group.

And this, more than anything else, is why features differ between National Armies. The members of the Joint Requirements Oversight Council (JROC) and the group that creates the Operational Requirements Document (ORD) directly decide the functional features (among many other functional characteristics) that must be in the weapon system. No particular feature gets into a requirements document without strong internal advocacy, and for every feature that someone claims is essential, there is someone else who is very skeptical of the need, particularly if it has cost associated with it. There is no Guerrilla larger than the Finance Guerrilla, and no ceiling taller than the Budget Line Item. While this turns out to be very frustrating to some end users, for example the guys who wanted a coffee grinder in the buttstock (Sharps rifle), not everyone gets everything they want in life.

I have been promised that the next life is much better, so maybe in Paradise I will get my coffee grinder back.

 

[barnbwt]

The "coffee grinder" was a generic grain grinder so poorly supplied troops could make their own milled starches from produce found in the farmland they fought through. Not quite as sillyas we always make it out to be

"Not adopting the AK was truly an example of not invented here."
Though not related, the AK and Garand share an eerie amount of commonality in the gas, bolt, and trigger systems

"I think the real reason some of the rifle designs since the 1940s omitted BHO was because the designs could not have an attached detachable box magazine reloaded with stripper clips"
Probably, but lots of designs also used clips themselves as the hold open for loading. What designs besides the AK, G3, and M16 couldn't take clips, though?

TCB

 

[Nom de Forum]

Whereas the Americans have a tradition of BHO devices, primarily there, in my opinion, so they could play the XTC game, the British Lee Enfield never had one, so there was not any core advocacy within the requirements group.

And this, more than anything else, is why features differ between National Armies. The members of the Joint Requirements Oversight Council (JROC) and the group that creates the Operational Requirements Document (ORD) directly decide the functional features (among many other functional characteristics) that must be in the weapon system. No particular feature gets into a requirements document without strong internal advocacy, and for every feature that someone claims is essential, there is someone else who is very skeptical of the need, particularly if it has cost associated with it. There is no Guerrilla larger than the Finance Guerrilla, and no ceiling taller than the Budget Line Item. While this turns out to be very frustrating to some end users, for example the guys who wanted a coffee grinder in the buttstock (Sharps rifle), not everyone gets everything they want in life.

American use of bolt hold open devices has nothing to do with "XTC games". The 1903 Springfield has a BHO device (mag follower), the M1 Garand had to have one to ensure clearance of the enbloc clip during ejection and to make reloading practical, the M14 had one, and so does the M16. Only the M16 has one for reasons other than reloading without removal and replacement of the magazine. They all have one partially for the reason of letting the soldier know his rifle is empty and to speed reloading.

As I mentioned in other words in a previous post, the British have apparently decided that a BHO device is an advantage since their current rifle has one. I am sure the cost of adding such a device is so trivial in comparison to other items of consideration that cost alone has very little to do with the decision. The problem preventing earlier adoption was most likely “if it was good enough for our (fill in the appropriate title of an ancestor) to not have them then we don’t need them”.

The "Coffee Grinder Sharps" was intentional not given to all soldiers because one was expected grind food for several soldiers. A wise cost cutting measure that in no way reduced combat effectiveness like the lack of a BHO device could in certain situations.

 

[Nom de Forum]

"I think the real reason some of the rifle designs since the 1940s omitted BHO was because the designs could not have an attached detachable box magazine reloaded with stripper clips"

Probably, but lots of designs also used clips themselves as the hold open for loading. What designs besides the AK, G3, and M16 couldn't take clips, though? TCB

I consider a detachable box magazine with a follower that holds the bolt back after the last shot to be a type (poor type) of BHO device.

Clips? I assume you mean stripper clips a.k.a. charging clips, not detachable box magazines. If so the answer to your question is any design that has an upper receiver or receiver cover that blocks the vertical insertion of a clip to refill a box magazine. Besides the three you listed can be added the FAL, CAL, FNC, AUG, SA-80, FAMAS, AR70, SIG 510, and several others. Some of them though have BHO devices that are obviously not there to permit reloading of the magazine with stripper clips but to speed-up the reloading of the rifle with a detachable box magazine.

 

[Willie Sutton]

Hey Willie does that Mig you jockey around still have the 37mm installed?

Yes, one NR- 37 and two NS-23's, both designs being recoil operated as well.

Sadly all three are (of course) BATFE spec demils, with the rear of the receivers removed, but the remaining components are still installed in the jet for weight and balance reasons. I was going to mention that the Russian autocannons are all recoil operated. I've handled live ones in Poland, and you ought to see the recoil spring on a 37mm recoil operated cannon. The tooling needed to safely disassemble and assemble one is pretty impressive.

Willie

.

 

[barnbwt]

Besides the three you listed can be added the FAL, CAL, FNC, AUG, SA-80, FAMAS, AR70, SIG 510, and several others. Some of them though have BHO devices that are obviously not there to permit reloading of the magazine with stripper clips but to speed-up the reloading of the rifle with a detachable box magazine.

For some reason I'd thought the FAL had an open receiver, but I was just thinking of the FN49 (that was one of the things they changed for the upgrade, obviously). But mainly I was noting that none of the designs that saw wide adoption --nor the majority of designs coming out at the time, were even clip-capable in the first place. I agree that BHO's help speed reloading, especially when the charging handle is far away from the magazine or opposite the weak hand, but I'm not sure about the aspect of them notifying the shooter the mag is empty. I mean, I guess a locked-back bolt implies you didn't just have a misfire when you pull the trigger and nothing happens, but issue arms are (supposed to be) so reliable that a dud-strike would be a true rarity. But getting back to speed of reload issue, I'm quite positive the need for a locked bolt to speed up reloading is extremely dependent upon where/how the charging handle is located, which might explain why it seems kind of random which guns have/don't have the device. Might simply be a procurement officer's personal preference that makes the decision.

Grossly off topic, though

Sadly all three are (of course) BATFE spec demils, with the rear of the receivers removed, but the remaining components are still installed in the jet for weight and balance reasons.

Yeah. That's why. . As big as those things are, being recoil operated, I imagine they've gotta be built like CAT rock hammers. True heavy machinery. If you ever feel like buying a lot of jet fuel, I'm sure there's a market for a demilled 37mm parts kit (esp. if your barrel was from before the import ban) . I'm sure there'd be enough left over for some lead ballast

TCB

 

[Nom de Forum]

For some reason I'd thought the FAL had an open receiver, but I was just thinking of the FN49 (that was one of the things they changed for the upgrade, obviously).

Upgrade? Perhaps a matter of opinion depending on what side of the pond you live on. The Brits adopted a FAL (L1A1) without, in Brit nomenclature, charging clip capability. On the other side of the pond the Americans tested the FAL (T-48) with an open top receiver that, in American nomenclature, was stripper clip capable. More interesting is the Canadians adopted a FAL (C1) with an open top receiver that is stripper/charging clip capable.

I agree that BHO's help speed reloading, especially when the charging handle is far away from the magazine or opposite the weak hand, but I'm not sure about the aspect of them notifying the shooter the mag is empty. I mean, I guess a locked-back bolt implies you didn't just have a misfire when you pull the trigger and nothing happens, but issue arms are (supposed to be) so reliable that a dud-strike would be a true rarity. But getting back to speed of reload issue, I'm quite positive the need for a locked bolt to speed up reloading is extremely dependent upon where/how the charging handle is located, which might explain why it seems kind of random which guns have/don't have the device. Might simply be a procurement officer's personal preference that makes the decision.

I usually feel the physical difference of the bolt locking back after the last round before seeing it and that cues me to reload. A "misfire" would cue SPORTS.

 

[Slamfire]

For some reason I'd thought the FAL had an open receiver, but I was just thinking of the FN49 (that was one of the things they changed for the upgrade, obviously). But mainly I was noting that none of the designs that saw wide adoption --nor the majority of designs coming out at the time, were even clip-capable in the first place

Maybe you could list more examples that did not have bolt open devices? I am aware, for really old rifles, the Mosin Nagant, the Krag, (US and Norwegian), the M1 Carbine, grease gun, AK 47, Sten gun, Schmeisser , SH41, all of the German Sturmgewehr ’s of WW2. Some of these I don’t have actual experience of handling, I don’t see a bolt release in pictures for the SH41, the Schimeisser, Bren, I see recesses cut into the receiver where the shooter pulls the bolt handle back to cock. I fired the Carl Gustav m/45, it does not have a bolt hold back device. I would be interesting in knowing what other submachine guns did not have bolt hold open devices. I looked at web accounts of the latest Chinese service rifles, they have bull pup designs that don’t have bolt hold open, then some models that do, it is obvious that a bolt hold open device is not a must have, simply a nice to have.

Cost is real, and those who ignore part cost only show their lack of a logistical background. Additional parts cost real money, no matter how much smoke is created to make it vanish, the real cost of even tiny parts is real and substantive. Let’s say a sell price for a bolt release is $10.00. Over a procurement of 6 million rifles, that is $60,000,000 in direct cost. The direct cost is actually a tiny fraction of the logistical burden of stocking the thing, accounting for the thing, subcontracting for it, storing it, maintenance procedures, gages, etc. Something that would cost $60,000,000 in direct cost would easily have a $100,000,000 life cycle cost, and I don’t see $200,000,000 of reasons for why a bolt hold open device is an absolute necessary.

Bolt hold open devices will cause malfunctions on their own. I have had a couple of lock backs on M1911’s when the magazine was not empty. I have had slide closures when the magazine was empty. I also have had bolt over rides on my AR15’s. If the AR bolt is accelerated a bit too much it will over ride the magazine follower. As such, as nice as a bolt hold open device is, it could give false positives, you think the chamber is loaded, but it is not, or it can cause a failure to fire just when you need the thunderstick to go bang. Relying on a bolt hold device can get you killed. I suspect that is why there are a number of fielded weapon systems that don’t have a bolt hold open device.

Using a bolt hold open device as a reason to reject a design appears to me, to be a phenomena of “Not An AR” (NAAR). Prior to NAARism there was “Not a Musket”, (NAM) which is why the 1873 Trapdoor came into inventory. It is the closest you can get to an 1861 Musket and still use a cartridge. The user does not like change. The user wants something better, only a little different, and totally rejects revolutionary change. Adopting a Martini Henry but loosing the side hammer, was a leap too far for the user. While the Remington rolling block had a hammer, baby does not want just any rattle, it wants its rattle, and only its rattle. Given a chance, the user will create definitions, excuses, must haves that lead to only one solution: same old, same old. You can see this in every US weapon evaluation. I read the troop evaluations on the M1911’s. At the end of each report is a recommendation that this new fangled pistol be rejected and the Colt SAA retained. Or a double action revolver, it all depended on what the user was familiar with. Pointy sticks had to be wrestled from the hands of troglodyte infantry before they would grasp stone tipped spears, and well into their retirement troglodyte NCO’s claimed that nothing was as ever good as their old pointy sticks. As can be seen from the historical record, Neanderthal tool technical was virtually unchanged for 200,000 years or more. Knuckle draggers, then and now, are not comfortable with change.


In so far as NAARism, would I trade off a bolt hold open device for simplicity and reliability. I don’t think the AR is the end of history, (for me, history ended with the M14) and even though the AR design provides an extremely fast magazine change capability, I would rather have a rifle that did not have so many magazine jams. This is one, while officiating an XTC match, I was able to take a picture of this jam:






Magazines are the greatest source of un reliability in the AR design, and it is all due to baby wanting only its rattle. You can read the historical record in the book, “US Rifle M14”. The infantry school did not want magazines, they wanted in block clips but would settle for stipper clips. They were used to a Garand and Garands were fed from incabloc clip. The infantry school claimed, that magazines were expensive, magazines were heavy, and that high capacity magazines lead to too much shooting. It was called "ammunition wastage". Shooting too many rounds at the enemy is considered wastage. Because of this the M14 has a stripper clip guide on top, the CONOPS of the day was that you were supposed to load the magazine from the top, while it was in the rifle, and if you search, you will find the term “semi detectable" magazine being used.



The FAL experiments of the time, loading from the top with ten round clipper strips, were an absolute failure, would have been a greater failure in the field, and no one adopted it. It was just an experiment to see if that would make the user happy. Stoner created lightweight, cheap, magazines thinking that would make them happy. It was not what the user wanted either, but it is what they got along with jams and misfeeds.

Sometimes the worst thing that can happen is to get what you think you want.

 

[Ar180shooter]

There have been a few successful recoil operated designs; however, they are usually more sensitive to dirt, heavier, and more complex to make than gas operated rifles. The reason you don't see more is that better systems have been developed. Gas pistons with rotating bolts have proven themselves as the best combination for lightweight and reliable autoloading rifles.

 

[briansmithwins]

Gas pistons with rotating bolts have proven themselves as the best combination for lightweight and reliable autoloading rifles.

Don't forget cheap. By locking a rotating bolt into a barrel extension you eliminate the need for a receiver that can take the firing stress.

BSW

 

[Ar180shooter]

Don't forget cheap. By locking a rotating bolt into a barrel extension you eliminate the need for a receiver that can take the firing stress.

BSW

True! I forgot to mention cheap. When you use a barrel extension, you can manufacture the rest of the receiver out of stamped steel (like the Sig 550) or an aluminum forging milled to final shape (like an Ar-15).

 

[briansmithwins]

When you use a barrel extension, you can manufacture the rest of the receiver out of stamped steel (like the Sig 550) or an aluminum forging milled to final shape (like an Ar-15).

Or plastic, like the ARX.

BSW

 

[barnbwt]

"The reason you don't see more is that better systems have been developed. Gas pistons with rotating bolts have proven themselves as the best combination for lightweight and reliable autoloading rifles."
Nah, I prefer to think of gas operation as merely a path we've chosen to follow for the time being; there is undoubtedly always something better out there. I think it remains to be seen whether or not recoil operation can be competitive, since we've only had a scant handful of attempts, themselves fairly primitive, and one 'modern' design, the Johnson, that was arguably an equal to any contemporary but for a few meager differences (note I said differences; a bayonet can cause failure to feed, but hot ammo won't exactly break a Johnson's not-an-op-rod, either). Given what has been learned about recoil systems, combined with what we've found is good, bad, and useful regarding gas systems and service/commercial rifles in general, it stands to reason a modern recoil operated gun could be designed that has many advantages of its own.

I think even rotating bolts won't stay around forever (I think falling-block automatics will eventually be developed, at which point a gun's length will be limited to the barrel plus the cartridge length)

The barrel extension concept is here to stay; it's physically impossible short of some alien-tech solution like magnetic or ionic bonding to hold the breech shut using a smaller/shorter means. What's beautiful about this concept, though, is practically any design there is can use a barrel extension in some fashion, so long as the bolt locks at or near the front. The structural receiver was only ever needed in designs locked at the tail of long bolt bodies (BREN) or for more modern designs being manufactured with antiquated techniques (Garand).

But back to recoil operation;
I've done some more research/asking around, and I think I've found a very compelling idea; basically it's a 1/2 scale Barrett M82. The Barrett uses leverage to throw the lighter bolt back faster than the barrel, so that heavy mass does not need to bounce nearly so much in order for the action to cycle reliably. Normally, that's why these guns kick so hard; the bolt plus barrel have to be going at the "escape velocity" when they unlock in order for the bolt to cycle completely. If leverage dumps some barrel momentum into the bolt as it parts ways, less recoil energy is needed to run the gun in the first place.

This is why gas-op guns have been so prominent; very efficient use of operating force to run the action. Early gas-ops had huge pistons, and were enormously overgassed. The gas port in the Hotchkiss Portative was like 2/3 the bore diameter. The piston was more than the barrel diameter, if memory serves, all for a LMG cartridge . If it wasn't so gawdawful heavy, the operating recoil had to have been insane. But, designers rapidly learned they could easily regulate and efficiently exploit the gas pressure, and designs have used and less and less of the total energy available to operate the gun since. The result is the lightest parts traveling the smallest distances at the slowest speeds, culminating (for now) with the H&K MP7, which is a teeny tiny AR-180 action powered by the meager gas volume of a PDW cartridge (albeit a hot-rodded one).

My point is, if a recoil operated gun can be similarly efficient in how it uses the recoil of a shot to cycle the gun, I wager it can be similarly effective, while also offering distinct advantages, disadvantages, and differences that all add up to more options for a shooter to select from.

What I foresee is a tube-based aluminum receiver setup with hand guard-length barrel shroud, using off-the-shelf AR barrels/extensions/bolt head assembly, mags, and FCG (if not complete or modified lower). The muzzle-half of the barrel would be exposed just like any other AR design, and the overall profile of the main receiver ('upper' if you must) would not be unlike the current DI art. What is different is how much hugely simpler it would be to make with more primitive facilities.

The operation would borrow elements from the Barrett "bolt accelerator" concept, but instead of direct mechanical leverage linking the bolt/barrel, a spring would be differentially charged between them, unloading its stored energy (the bulk of the recoil experienced by the barrel) into the bolt body upon unlocking. Designed appropriately, recoil would be less than for an unbraked DI action. Initial recoil goes into a soft recoil spring and towards charging the accelerator spring instead of the shooter's shoulder. By the time the barrel hits its stops, the bullet is both long gone and the barrel has lost nearly all its momentum. At that point, the bolt would require the same inertia as an AR to complete its circuit. So, you have a softer-recoiling rifle that moves around slightly more (maybe) between shots owing to its larger, but slower moving, cyclic mass. It is entirely possible the setup would have an insanely high cyclic speed, too (that's fairly common for short recoil actions, but of course highly dependent on the unique dynamics of a given design)

Advantages would probably be similar to what they are in pistols; large degree of flexibility in both ammo and barrel lengths, so long as the reciprocating elements can be buffered (or braked) sufficiently. Suppression would likely be better over a gas system, so long as the system can be boosted sufficiently. Depending on how the spring accelerator is designed, it would actually cushion the bolt head as it returns to battery, which could only help both felt recoil and operating noise. Good chance it'd be cleaner than a DI, or possibly even long-stroke gas systems, too.

Disadvantage would be that, yes, if you rest the non-shrouded portion of the barrel on something, or attach a bayonet, you would affect the cycle. Charging the gun would likely be a bit odd; you can either draw the bolt straight back and drop the barrel partway during the pull, or initially unlock the bolt through some other movement before pulling it back. There would also likely be a longer lower limit on barrel length, since buffer spring stiffness would have to skyrocket to protect the action as the barrel got lighter and lighter. That, or you'd require more and more obnoxious muzzle brakes for an SBR build . The big disadvantage would be people calling the gun a "Stoner's Johnson"

TCB

 

[sawdeanz]

The Barrett uses leverage to throw the lighter bolt back faster than the barrel, so that heavy mass does not need to bounce nearly so much in order for the action to cycle reliably.

This just reminded me about the existence of the Russian AN-94, which I'm pretty sure is recoil operated. It has a smaller lighter bolt that reciprocates twice as fast as the barrel, enabling it (with some other gimmicks) to fire 2 shots before the recoil of the barrel hits the shooter.

Actually looking it back up it is actually gas operated for some reason, but it still shows that there is at least one military that is considering a rifle with reciprocating barrel. I don't know why a similar design couldn't be incorporated with pure recoil-operation, since the AN-94 is clearly to complicated for serious work, especially with both disadvantages of gas and recoil operations.

 

[Nom de Forum]

I looked at web accounts of the latest Chinese service rifles, they have bull pup designs that don’t have bolt hold open, then some models that do, it is obvious that a bolt hold open device is not a must have, simply a nice to have.

So as an example of deciding the value of paying for the inclusion of a Bolt Hold Open feature you choose rifles designed based on the values of the Chinese Army. The Chinese Army historically has little experience being outnumbered and needing to use every possible advantage to increase individual rate of fire to gain fire superiority. The Chinese Army historically does not share a concern for the lives of individual soldiers anything like that of the United States and other western democracies. The Chinese Army historically is willing to use massive numbers of soldiers in a charge to overwhelm opponents regardless of casualty percentages no western democracy could accept. The Chinese are not a good role model for emulation in combat rifle design or combat tactics for western democracies. Neither are the Russians. Both since the 1970s are emulating the design philosophy of the M16 (lighter weight, smaller caliber, better ergonomics) more than western designers are emulating Russian and Chinese design philosophy. The Chinese are apparently still sorting out the fact that just because Russians left off BHO it is not something to be copied or used to inspire new designs. The Czechs and Yugos figured that out long ago with the Vz58 and Yugo M64.

Let’s say a sell price for a bolt release is $10.00. Over a procurement of 6 million rifles, that is $60,000,000 in direct cost. The direct cost is actually a tiny fraction of the logistical burden of stocking the thing, accounting for the thing, subcontracting for it, storing it, maintenance procedures, gages, etc. Something that would cost $60,000,000 in direct cost would easily have a $100,000,000 life cycle cost, and I don’t see $200,000,000 of reasons for why a bolt hold open device is an absolute necessary.

Bolt hold open devices will cause malfunctions on their own. Relying on a bolt hold device can get you killed. I suspect that is why there are a number of fielded weapon systems that don’t have a bolt hold open device.

Bolt hold open devices are very reliable, very mechanically simple, and very inexpensive to manufacture and install on a rifle. So reliable that most modern semiautomatic pistols have them and that trend is evident in modern service rifle designs post 1950. Malfunctions are very rare. It is far more likely you will be killed in some combat situations because you are unaware your rifle is out of ammunition than because of a BHO device malfunction. The expense of adding a bolt hold open feature is probably less than 1% of the total cost of a large contract for rifles. In the U.S. Army the M16 bolt catch, pin, plunger and spring is almost never in need of replacement. The main problem with malfunctions is due to not taking bad magazines out of service soon enough. Bolt over-rides are not caused by BHO devices. Not using good quality, undamaged magazines is what causes over-rides. Over-rides can happen with any autoloading magazine fed firearm. You will get no argument from me defending the compromised design of M16 magazines but even an AK with its well designed magazine can experience an over-ride.

Using a bolt hold open device as a reason to reject a design appears to me, to be a phenomena of “Not An AR” (NAAR). Prior to NAARism there was “Not a Musket”, (NAM) which is why the 1873 Trapdoor came into inventory. It is the closest you can get to an 1861 Musket and still use a cartridge. The user does not like change. The user wants something better, only a little different, and totally rejects revolutionary change. Adopting a Martini Henry but loosing the side hammer, was a leap too far for the user. While the Remington rolling block had a hammer, baby does not want just any rattle, it wants its rattle, and only its rattle. Given a chance, the user will create definitions, excuses, must haves that lead to only one solution: same old, same old. You can see this in every US weapon evaluation. I read the troop evaluations on the M1911’s. At the end of each report is a recommendation that this new fangled pistol be rejected and the Colt SAA retained. Or a double action revolver, it all depended on what the user was familiar with.

Magazines are the greatest source of un reliability in the AR design, and it is all due to baby wanting only its rattle. You can read the historical record in the book, “US Rifle M14”. The infantry school did not want magazines, they wanted in block clips but would settle for stipper clips. They were used to a Garand and Garands were fed from incabloc clip. The infantry school claimed, that magazines were expensive, magazines were heavy, and that high capacity magazines lead to too much shooting. It was called "ammunition wastage". Shooting too many rounds at the enemy is considered wastage. Because of this the M14 has a stripper clip guide on top, the CONOPS of the day was that you were supposed to load the magazine from the top, while it was in the rifle, and if you search, you will find the term “semi detectable" magazine being used.

The FAL experiments of the time, loading from the top with ten round clipper strips, were an absolute failure, would have been a greater failure in the field, and no one adopted it. It was just an experiment to see if that would make the user happy. Stoner created lightweight, cheap, magazines thinking that would make them happy. It was not what the user wanted either, but it is what they got along with jams and misfeeds

.

Your origin story of the 1873 “Trapdoor” is all wrong. The Trapdoor system was adopted because it permitted initially cost efficient conversion of existing muzzle loading rifles after the Civil War. The British did the same thing prior to the adoption of the Martini-Henry. Your comments about the Trapdoor, Martini-Henry, Remington Rolling Block, 1911, M14, FAL, and M16 are out of context and inaccurate resulting in distortion of history. Frankly, there is so much distortion needing correction I just don’t have the desire to spend so much of my time correcting them. Slamfire1 you can post errors with a few words faster than I can make the necessarily long worded corrections. Your point of view on bolt hold open devices is on the wrong side of history. Whatever future designs are created they will more likely than not have some type of device, other than failure to fire after pulling the trigger, that notifies the user the rifle is empty.

 

[Slamfire]

Nah, I prefer to think of gas operation as merely a path we've chosen to follow for the time being;

I agree, Armies and design groups have biases. After reading enough on the early history of firearms, I found statements that lead me to conclude the Germans did not "like" gas operation and the historical evidence of their firearms makes me conclude they had a bias against gas operation. I recall reading a statement to the effect that gas operation caused erosion around the gas port, which it does. And so what. But, that was just one of the excuses used by the Germans. The majority of their machine guns and assault rifles were delayed blowback.

Paul Mauser's M1905 was a short recoil, his M1916 automatic rifle was a delayed blowback and it required greased cartridges to function. I suspect Mauser did not try to make a gas operated rifle because he knew it would not sell.

I think it remains to be seen whether or not recoil operation can be competitive, since we've only had a scant handful of attempts, themselves fairly primitive, and one 'modern' design, the Johnson, that was arguably an equal to any contemporary but for a few meager differences (note I said differences; a bayonet can cause failure to feed, but hot ammo won't exactly break a Johnson's not-an-op-rod, either). Given what has been learned about recoil systems, combined with what we've found is good, bad, and useful regarding gas systems and service/commercial rifles in general, it stands to reason a modern recoil operated gun could be designed that has many advantages of its own.

I agree, just don't know if other than same old/same old is the reason why everything has gone gas operated.

 

[Nom de Forum]

Given what has been learned about recoil systems, combined with what we've found is good, bad, and useful regarding gas systems and service/commercial rifles in general, it stands to reason a modern recoil operated gun could be designed that has many advantages of its own.

barnbwt,

I think there will continue to be much resistance to recoil operated combat rifles because of concerns about moving barrels, lack of need for flexibility to fire cartridges of greatly varying characteristics, user experienced shooting characteristics, and most importantly no significantly greater advantages prior to the adoption of radically new small arms technology. If a new combat rifle design used recoil for operation it would have to be incredibly better than existing gas designs to change the minds of procurement authorities.

 

[Ar180shooter]

"Nah, I prefer to think of gas operation as merely a path we've chosen to follow for the time being; there is undoubtedly always something better out there."

I feel this should be qualified. There is always something better out there when new technology is developed. I'm not convinced there is something that improves on gas operated, piston driven lightweight automatics. A new recoil driven design may improve on some aspects, but as long as we are using brass cased ammunition, I do not think any advantages will outweigh the disadvantages of adopting such a system.

"I think it remains to be seen whether or not recoil operation can be competitive, since we've only had a scant handful of attempts, themselves fairly primitive, and one 'modern' design, the Johnson, that was arguably an equal to any contemporary but for a few meager differences (note I said differences; a bayonet can cause failure to feed, but hot ammo won't exactly break a Johnson's not-an-op-rod, either)."

There were lots of attempts in the early days, few were successful in military firearms, most were unsuccessful. They were, quite simply, inferior to gas operated arms. The Johnson was an interesting design, but it was fragile, unreliable and expensive to produce compared to the Garand. It was not comparable, because you could arm multiple soldiers with the more reliable Garand for the same cost as 1 Johnson.

"Given what has been learned about recoil systems, combined with what we've found is good, bad, and useful regarding gas systems and service/commercial rifles in general, it stands to reason a modern recoil operated gun could be designed that has many advantages of its own."

The Beretta/Benelli inertia system is an example of this. It is appropriate for sporting arms. For military arms, it is not sufficiently robust and reliable.

"I think even rotating bolts won't stay around forever (I think falling-block automatics will eventually be developed, at which point a gun's length will be limited to the barrel plus the cartridge length)"

Possibly, but probably not. The big issue that I can see with a falling block automatic is the extraction and reloading cycle. You would need separate pieces to remove spent casings and insert new cartridges. By using caseless ammunition, you do remove the extraction cycle, but this still doesn't completely relieve the problem. Such a mechanism would have to be quite complex. This takes away from reliability, and adds to cost and weight. In addition, modern gas operated firearms are more than sufficiently compact. The biggest advances in the next 25 years will be in material technology, lightening already light designs.

"But back to recoil operation;
I've done some more research/asking around, and I think I've found a very compelling idea; basically it's a 1/2 scale Barrett M82. The Barrett uses leverage to throw the lighter bolt back faster than the barrel, so that heavy mass does not need to bounce nearly so much in order for the action to cycle reliably. Normally, that's why these guns kick so hard; the bolt plus barrel have to be going at the "escape velocity" when they unlock in order for the bolt to cycle completely. If leverage dumps some barrel momentum into the bolt as it parts ways, less recoil energy is needed to run the gun in the first place."

How is any of that an advantage over a gas operated firearm? Such a system is not any less expensive, lighter or more reliable than a gas operated system in conventional light arms.

"This is why gas-op guns have been so prominent; very efficient use of operating force to run the action."

They are efficient and modern ones are very light weight.

"My point is, if a recoil operated gun can be similarly efficient in how it uses the recoil of a shot to cycle the gun, I wager it can be similarly effective, while also offering distinct advantages, disadvantages, and differences that all add up to more options for a shooter to select from."

It's not just about being able to operate the gun. I'm quite sure one could develop a recoil operated small arm that can compete with the M16 in almost every way... except cost would be astronomical and there would be no practical advantage.

"What I foresee is a tube-based aluminum receiver setup with hand guard-length barrel shroud, using off-the-shelf AR barrels/extensions/bolt head assembly, mags, and FCG (if not complete or modified lower). The muzzle-half of the barrel would be exposed just like any other AR design, and the overall profile of the main receiver ('upper' if you must) would not be unlike the current DI art. What is different is how much hugely simpler it would be to make with more primitive facilities."

A DI system on something like a stamped Ar180 upper/lower would be much simpler.

"The operation would borrow elements from the Barrett "bolt accelerator" concept, but instead of direct mechanical leverage linking the bolt/barrel, a spring would be differentially charged between them, unloading its stored energy (the bulk of the recoil experienced by the barrel) into the bolt body upon unlocking. Designed appropriately, recoil would be less than for an unbraked DI action. Initial recoil goes into a soft recoil spring and towards charging the accelerator spring instead of the shooter's shoulder...."

The Barrett system is not inexpensive as it requires very precise tolerances to be reliable. Not exactly something you want in an inexpensive and easily produced arm. That's the thing about gas operated firearms... they can be reliable, even with loose tolerances. This is why I don't think any other system will replace them until radically new technologies are developed.

"Advantages would probably be similar to what they are in pistols; large degree of flexibility in both ammo and barrel lengths, so long as the reciprocating elements can be buffered (or braked) sufficiently. Suppression would likely be better over a gas system, so long as the system can be boosted sufficiently. Depending on how the spring accelerator is designed, it would actually cushion the bolt head as it returns to battery, which could only help both felt recoil and operating noise. Good chance it'd be cleaner than a DI, or possibly even long-stroke gas systems, too."

What are you basing any of that on? Seriously, you're just making most of that up without any real evidence to back it up.

"Disadvantage would be that, yes, if you rest the non-shrouded portion of the barrel on something, or attach a bayonet, you would affect the cycle. Charging the gun would likely be a bit odd; you can either draw the bolt straight back and drop the barrel partway during the pull, or initially unlock the bolt through some other movement before pulling it back."

So, why would anyone want to develop such an over-complicated and temperamental beast again?

 

[briansmithwins]

In theory recoil operation eliminates parts (gas piston, op rod) and doesn't have problems with gas port erosion or fouling in the action.

In practice, the extra parts that recoil actions require (barrel mount, buffering, heavier/more complex receiver) eliminate the weight advantage, the problems with gas port erosion aren't significant (before the barrel is shot out), and fouling hasn't been a bad problem since black powder and corrosive primers.

Gas operation isn't perfect, but the alternative is usually worse.

BSW

 

[barnbwt]

20,000 Character Limit, Baby!!!

Man, this is where I hate the "Forum" format in regards to technical discussion. Everybody dissects everyone's multiple arguments sentence by sentence, which they made in a single post in the first place because that's the only practical way to make a complex/multi-point statement about something like a firearm action with many technical details. The result is the number of points made by each poster is literally multiplied by the sum of all those that came before it, and the thread collapses under its own weight (I'm thinking of that thread about the dynamics of the 1911's operation, here. I think Nom was present for that Battle Royale )

:banghead::banghead::banghead:

Please try to bear with me, AR180; I'll try to answer/rebut a lot of your points, but there's no way we can all hit all of eachothers' and keep the thread usable

"There is always something better out there when new technology is developed"
I agree, but since I'm kind of talking about a new technology with regards to recoil operation (since obviously the current art is inferior), this is kind of a redundant statement. Maybe not "new" as in revolutionary, but at least more evolved than a 30-06 Johnson rifle. The Garand fails in practically the exact same ways in comparison to the M16 (or anything else), and it was really not much different in execution than the Johnson (meaning the materials, desired usage/features, overall layout, and "state of the art" that correlates all contemporary designs with the eras of their creation)

There also seems to be some misunderstanding about such a new concept making its way into an issued arm (or rather, our issued arm). There's no way some new technology is gonna overcome the internal bias, idiocy, and illogic infecting our --or any-- procurement process to 'win the day' solely based on its technical merits. It's fun to think about what would be the best for our boys, but it's a foregone conclusion that they won't be getting it, except by accident. So I'd much rather keep the 'practicality/realistic use' discussion centered more on the commercial side of things, which biased though it is, does seem to respond more readily to legitimatly good ideas. Most of the time. I'm aware all the modern competitive tactical shooters more or less desire the same feature set as soldiers, which is fine, but the procurement angle is a discussion area I simply can't comment on because of both ignorance and irrelevance to recoil operation itself.

"There were lots of attempts in the early days, few were successful in military firearms, most were unsuccessful. They were, quite simply, inferior to gas operated arms."
This was hardly the case prior to WWII, and not even necessarily the case by the end of WWII. The main thing the war proved to everyone, was that gas ports really don't amount to a hill of beans, and that gas operation is fine if you have non-corrosive ammo (or take appropriate provisions against corrosion). I'd argue that WWI was actually the war that proved bolt guns needed to go bye-bye, but the second war came too quickly for everyone to have upgraded fully. And l like I said before, I think gas systems are more easy to 'tune' during development than recoil operation, since their timing variables are independent of the geometry (weight) of the functional parts. That means you can delay or speed, lighten or embolden, and precisely meter exactly how the gun cycles from the gas block. Basically, if you design a straight-pull bolt action that works reliably, you are basically guaranteed a gas system can be fitted to it and run well.

Recoil operation is inherently dependent upon its particular set of components to cycle. Arbitrarily decide to make the barrel too heavy in the early design phase --won't work without a recoil booster that makes the gun kick hard. Make the bolt travel too short based on an initial guess early on, and the gun may cycle too fast for the magazine. These things are much easier to tune/time on a gas operated design, but require very significant changes to a recoil design. Changes that themselves have ramifications.

But simply because recoil operation may be harder to get right, does not necessarily mean that it yields inferior results. The end product is what matters, right? Let's at least assume that a properly tuned recoil action can be developed for whatever hypothetical scenarios we can conjure, just as I'll assume any supposed Stoner action is properly tuned (that one took a while to get right, as well)

"The Beretta/Benelli inertia system is an example of this. It is appropriate for sporting arms. For military arms, it is not sufficiently robust and reliable."
I had a Franchi I12 shotgun using this action. The only gun I sold, and for 2 reasons; 1, the gun did not fit me well at all; happens to everyone with every gun. 2, the gun jumped around like crazy as part of its necessary operating cycle. The problem with the inertia system, is that the shooter becomes a critical part of the recoil tuning balance equation. I tended to be either too heavy or too rigid for the gun to cycle properly (I plant myself firmer than I probably should when shooting clays), forcing me to actively loosen my shouldering of the gun; no bueno (ouch). It's bad enough that a long recoil system slams the bolt+barrel directly into the shooter through a frame and buffer; the inertia system slams the whole dang rifle into your shoulder. So you must either have a really squishy bad, or wimpy pectoral muscles, or stand with your feet somewhat close together so your upper body can rock around like a punching clown

"The big issue that I can see with a falling block automatic is the extraction and reloading cycle. You would need separate pieces to remove spent casings and insert new cartridges."
Technically, you need separate pieces for those functions in a reciprocating bolt design as well. They just move as a unit in that format, whereas in a FB, they don't. PM me if you are actually interested about this concept, since it's really outside the scope here (I shouldn't have brought it up as conjecture)

"How is any of that [Barrett accelerated-short-recoil] an advantage over a gas operated firearm? Such a system is not any less expensive, lighter or more reliable than a gas operated system in conventional light arms."
I'm no expert, but I suspect the Barrett is quite a bit lighter than some of the gas-operated 50cal rifles out there with same-class barrel lengths/profiles (granted, the Barrett is a bit of a pig, since that undoubtedly helps the gun cycle more efficiently, so perhaps not). It's hard to find whether posted weights are loaded or not (makes a big difference on a 50cal), but even the DI Serbu 50cal* is only about 5lbs lighter unloaded (I don't know if the Barrett weight online is w/ mag or not). At any rate, it doesn't appear to be a major difference at least for that type of rifle with such large barrelverall weight ratio.

As far as cost and reliability, I won't claim to know how much a non-existent hypothetical rifle would chart . Barrett seems to think they are the only player out there*, and that would possibly give a reason for the massive cost differential over the Serbu (Barrett-10000$; Serbu-7000$). But as far as simplicity, I'm working on a design similar to what I've described; it looks like the spring-loading function I describe can be effected with a single rotating collar about the chamber area and a single stiff spring to drive it (there would be no need to cushion the barrel assembly itself with another spring). Still a work in progress, I know, but theoretically you only need a single additional moving component over a typical short-recoil to make the concept work. More work is still needed on the particulars, though...

"They [gas-op guns] are efficient and modern ones are very light weight."
But lets keep in mind why they are both efficient and light. Early gas guns that managed to actually work well, like the Garand, were not exactly great in either area. Eventually, advances in materials (aluminum and sheet metal) and mechanical design (short stroke operation, the barrel extension concept, modularity as a design goal) yielded the AR180; arguably the dead end (or 'culmination' if that sounds better) of the piston-operated gun development path. Subsequent improvements in materials like polymer have not been nearly as marked an improvement (see again ARX-160), and very little as far as modularity or ergonomics/layout has changed much at all.

Apply the '50's love of large caliber, select-fire, LMGs to the Johnson rifle (along with some terrible Israeli execution ) and you get the ill-fated DROR light machine gun. Apply the same exact materials advances and design goals as the AR10/AR15 to something like the Johnson rifle, and you would obviously expect something far different to come out than what we've seen so far. I, personally, have not seen convincing proof/reasons/arguments for why such a result could not be an improvement. Partially because proving a negative is impossible P), partially because I'm a technological optimist when it comes to guns, and partially because what I do understand about recoil operation strongly suggests it carries a set of strengths and weaknesses just like gas operation, and none of them inherently precludes an effective design execution.

"I'm quite sure one could develop a recoil operated small arm that can compete with the M16 in almost every way... except cost would be astronomical and there would be no practical advantage."
Care to elaborate, specifically? Would the barrel bushings make it cost tons more, or the two return springs? Because that's basically all there is to a recoil action that isn't also in a gas-op action (they both need a receiver tube, bolt, and trigger group). What you'd lose is the gas block, gas port, gas tube, bolt carrier in its entirety, and the need for a complex CNC machined upper receiver. The lower would basically be unchanged, unless you opted to roll the buffer tube into the now completely tubular upper receiver for additional simplicity at the cost of reduced modularity.

I'm not saying I positively disagree with you --I can't since there's no recoil rifle design to actually compare to-- I just don't see the likelihood of enormous additional complexity or cost. Now, the rotating-breech H&K G11 with its caseless baloney, that carries some pretty obvious intrinsic costs over pretty much every action type that's been tried.

"A DI system on something like a stamped Ar180 upper/lower would be much simpler."
Putting aside the honest question of why no one's tried that yet (seriously; why hasn't anyone? That's a legitimately good concept to pursue, and a pretty obvious one, to boot. All the new short stroke piston guns blatantly crib off the AR180, so why not DI?), stamped receivers and are actually pretty hard to make without tooling. Anything more complicated than the AK's two straight bends basically needs to be farmed out to a full-on press house. For an industrial undertaking, that's not a big deal, but I like to be able to build my guns (I know, not a concern to most, but a real one to me). If 80% builders and build parties are any clue, there is actually a real demand out there for a quality, home-buildable rifle platform that doesn't rely upon foreign-sourced parts that are both artificially cheap and finite in supply.

Picturing how both concepts could be laid out, I think they'd be rather similar in complexity: a non-structural trunnion holding the AR180 barrel/gas system set into the front of the receiver shell, with your return springs extending back to a non-structural rear trunnion (built into the upper or the lower), all sitting atop a self-contained lower. The recoil rifle would have the barrel assy sitting inside the receiver tube, guided by a few cam pins in slots, or something, with a recoil spring extending back to the removable end cap, all sitting atop a self-contained lower.

They're different, but not totally far off in terms of relative complexity. At least in parts count, the recoil action likely has fewer, but its not like the extra parts of a short stroke tappet action are all that complicated anyway. If a DI gas system (AR or the simpler/messier AG42) were used, I'd think the moving parts would be fewer, but the total number about the same. I just think it's too close to definitively call for any modern, modular design with a non-structural receiver. At least not until more specific designs are being considered. It's not like recoil vs. gas-piston operated pistols where it's a night/day difference for any number of reasons.

"The Barrett system is not inexpensive as it requires very precise tolerances to be reliable. Not exactly something you want in an inexpensive and easily produced arm. That's the thing about gas operated firearms... they can be reliable, even with loose tolerances."
The Barrett is also firing a very powerful cartridge with very grave consequences if things don't work right. "Service" rifles do too, but it's still quite different as it relates to 223 class cartridges. 223 doesn't require anything close to the kind of dwell time as 50bmg in order to unlock the breech safely, nor the momentum required to extricate a stuck case and feed a new one. In order to do those things without overpowering the shooter by putting more recoil into the system, all the parts must be high quality so no energy is wasted. There's nothing particularly special about the feed, extraction, or lockup operations themselves that necessitates especially precise manufacture compared to other mechanisms. I think the 'sniper' accuracy requirements are more the driving factor, there.

Gas operated guns can be reliable with loose tolerances, but only by 'over gassing' the system. The AK is the most well-known example. This occasionally manifests itself in blown off gas covers . The trouble is, in order to drive the "loose" guns hard enough to cycle reliably, you must impart a lot of needless energy into guns at the nominal or "tight" areas of the spectrum. That means your pistons must be tougher, your gas tubes/blocks stronger, your frame buffering more capable...basically you have to bulk up the rest of the gun so it can run rougher without breaking.

I would also argue that, at least with the present state of the art, the axiom does not apply to direct impingement guns. The fact is that deviation from nominal tolerances seems to have an outsized effect on Stoner gas systems compared to others, with piston rings, gas tubes, bolt carrier weights, and buffer springs requiring tweaking when the design must operate in non-optimum conditions (short barrel, suppressor, bad piston/bolt tolerance, bad gas port size). The main thing the Stoner design has going for it in this regard, is that it is so easy to discard & replace the offending portion of the puzzle and replace it with another that probably won't show the same variance. It works great on a large, well supplied scale (or one where parts suppliers want to make it rich ), but can be very frustrating to a home builder or smith seeking to modify a functional design. Not everyone's concern, I know, but my/many others' preference tends towards adaptability vs. disposability

"What are you basing any of that [supposed recoil operation advantages] on? Seriously, you're just making most of that up without any real evidence to back it up."
Maybe I should have elaborated; back in that ginormously-long and intense 1911 discussion I alluded to earlier, we all realized through the power of math that recoil operation is very self-regulating so long as you can adequately buffer the system. To shoot a bullet heavy enough to unlock the gun earlier solely by virtue of its additional mass, it had to be more dense than Uranium , and anything less dense would eat up your powder volume with the extra bullet length required. Conversely, lighter and lighter bullets are limited in how much recoil can be imparted to the action by the mass and peak velocity than be attained by the powder itself and a theoretical 0gram bullet; as I recall, such a situation cannot generate enough 'oomph' to unlock the gun. In short, the conclusion was that recoil actions do not need to be timed for different loads the same way as gas systems are. The catch is in cushioning the hard-recoiling situation while maintaining reliability for the lightest bullets possible. Do keep in mind this was for 45acp; 223 is neither fat nor stubby, so those limits may not be as absolute (probably not in the case of heavy bullets since there is so much powder capacity)

Also, once more, expecting me to present real-world evidence for a theoretical exercise that, again, does not exist, is a bit unfair. The best I can do is examine the physics/kinematics of such an operating concept, and posit how they would seem to differ from currently available gas operated actions. The purpose is to ponder how such a non-existent technology might differ from what we have now, so we could then debate/ponder whether or not it constituted an improvement or not. A 223 with a recoil impulse that is possibly 'smoothed out' but possibly a bit higher overall seems like it could potentially be attractive. It could feel like a roller-lock gun but run cleaner; what's not attractive about that?

"So, why would anyone want to develop such an over-complicated and temperamental beast again?"
No one's asking you to; you'd just be buying it ready-made. Maybe that's the issue, here. I'm sensing some outright hostility to the very concept as presented, with very few specific reasons justifying blanket statements like "it can't" or "it won't". FWIW, even those dead-simple blowback pistols took years to develop, and the locked-breech designs took professional design houses with many engineers/inventors even longer. Those early experiences and research has at least formed a 'road map' for present designers, so we can at least take an efficient path to a design solution instead of flailing randomly (with Blish locks and rifling-torque ). Compared to other dead-end concepts like toggle lock, tilting bolt/flap, blowback, blow-forward, and gas traps, recoil operation looks downright sensible.

Neither the Garand nor the Johnson were the 'best gun' for WWII (see: FN49), but the Garand is what we took to the dance, and forever colored our biases with. Just as the manually-operated guns colored future preferences for undrilled barrels ("why, those barrels have to be 30 inches long to shoot accurately. They could never tolerate such a disruption as a gas port. No we don't understand the effects of pencil barrels and wooden forestocks on accuracy" :banghead. The fact there is such a demonstrable cause for bias in the firearms design (that's not even getting into whether or not it is actually impacting the designs out there), and the fact that recoil operation works stunningly well for a certain class of firearm (pistols), and the fact that all firearms technology has evolved substantially since recoil rifles were last tried, strongly suggests they at least warrant a thorough examination for viability.

If they're still not a contender, I vote we check again in fifty years to see if they're better for shooting the standard caseless ammo at renegade cyborg bodies, or better for whittling out with files in caves to combat The Rise of the Machines, or for integrating into a do-all cybernetic arm (all three sides of the fight, there )

TCB

*"As the first and only semi-automatic .50 caliber rifle available..." --Barrett M82 webpage

 

[barnbwt]

"Gas operation isn't perfect, but the alternative is usually worse."

Agreed. Definitely the case thus far, anyway. But it's just so darn effective in semi-auto pistols...there's just gotta be some sort of utility in other areas of the design space. Like I wrote (somewhere in the sea of that last post ) above, it's possible that advances in other parts of firearms tech, like ammo, materials, and design conditions, have made the recoil action more attractive than when it was last tried.

After all, you try pitching an early gas operation to German generals when ammo was corrosive and barely reliable. Jams galore, corrosion, complication, a real pain the rear to operate compared to a bolt gun, that's for sure. Heck, try pitching a perfected AR relying on aluminum to Germans prior to WWI

"In practice, the extra parts that recoil actions require (barrel mount, buffering, heavier/more complex receiver) eliminate the weight advantage, the problems with gas port erosion aren't significant (before the barrel is shot out), and fouling hasn't been a bad problem since black powder and corrosive primers."
I'm picturing/working on an extruded tubular aluminum receiver with a couple simple slots to guide the internal parts on. Hard to argue its more complicated than the hot mess that is the AR receiver in its 'evolved' form. The thing's about as elegant as a Krag at this point with that forward assist . Yes, I'm aware that complex machining has become less of an obstacle in recent years to industrial manufacturers, but that's hardly an argument to say it does not matter at all. Considering both designs use a circular-profile bolt/barrel of the same size, the receiver would be very similar from the chamber back; and from the chamber forward, don't most modern AR's have an aluminum tube for a hand guard extending to the gas block?

Would there be areas where complexity increases? Undeniable. Would there be others where it disappears? Probably.

TCB

 

[Jim Watson]

Anybody want to revive the primer setback action?
The Garand design didn't work well when they went to MR and IMR powders more progressive than Pyro DG. But surely our rocket scientists can adapt.

 

[Slamfire]

Recoil operation is inherently dependent upon its particular set of components to cycle. Arbitrarily decide to make the barrel too heavy in the early design phase --won't work without a recoil booster that makes the gun kick hard. Make the bolt travel too short based on an initial guess early on, and the gun may cycle too fast for the magazine. These things are much easier to tune/time on a gas operated design, but require very significant changes to a recoil design. Changes that themselves have ramifications.

I broke out my Brassey's and looked at the section on short recoil. The author called the MG42 mechanism, a roller bolt, short recoil, accelerator mechanism, an extremely efficient mechanism. I also browsed my book on the roller bolts and something I think germane to this discussion is the amount of analysis that goes into designing a successfully "half locked" delayed blow back mechanism. The book "Full Circle" shows some of the force diagrams. At least for the roller bolt, calculations for mass, angles, forces, the kinematics of the system, is quite involved. This has to be carefully done or the mechanism will either have too much energy, or too little. Gas operated systems, you can move the gas port up and down the barrel, change the port size, there is more leniency after preliminary design to twiddle with things.

So, maybe that is one reason recoil mechanism are not that common, it takes more work up front!

Just looked at the FAMAS mechanism. It is not a gas mechanism, nor is it a short recoil mechanism, Wiki calls it a lever delayed blowback. This is one of the few service rifles that is does not use a gas operated mechanism. Nor does it have that "militarily essential" bolt lock!

 

[Mman]

There would be more recoil operated rifles if they didnt have to have minimum 16 inch barrels. The longer the barrel the more problems you have with recoil operation in a rifle that is intended to be carried and fired by one person. If short barreled rifles had a mass market (no nfa bar to over the counter sale) then recoil operation would be much more feasible. Less length and weight of barrel slamming around means simpler and more reliable. That is why it works so well on pistols.

 

[barnbwt]

"So, maybe that is one reason recoil mechanism are not that common, it takes more work up front!"
That's my working theory
"There would be more recoil operated rifles if they didnt have to have minimum 16 inch barrels."
That's my other working theory

How sweet & simple would a recoil-locked SBR in a super-hot PDW cartridge sized for minimal overpressure in the barrel be? The MP7 is supposedly quite unpleasant to shoot because its little gas components have such a tiny window to do their thing, that they must accelerate/collide extremely violently. They also have way too short a barrel for the cartridge they chose, so overpressure is terrible (as is erosion I have to assume). Probably the reasons that steaming pile has 6000 round service life, too

An action that is initially 'cushioned' from the shooter by the recoil spring, is truly locked breech, maintains minimal muzzle overpressure, and is as reliable as recoil pistols have proven to be, would be pretty sweet as a defense or plinking gun . Probably even more fun on full auto (not that we'd do that without a proper SOT/license )

TCB