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Idea for a gas operation
- Thread starter Cutaway
- Start date
I am not sure who beat whom on the patents, but MAS in France had a semi-auto gas impingement system rifle working in 1938 (The MAS Mle 38), although production didn't begin until 1940 after it had been slightly modified and renamed the Mle 40. (The Germans upset plans for mass production.)
The ejection port cover was not put on the AR-15 because the Army wanted it; it was on both the AR-10 and AR-15 from day one. I handled AR-10's and AR-15's with the old "upper trigger" and they had port covers.
To me, the main advantage of the AR-18 was the bolt riding on rods, like the M3/M3A1 SMG. While the rifle still used a port cover, the rod system made dirt and garbage in the system pretty much irrelevant as there was plenty of room for it. The takedown system, though, needed the same kind of operating spring capture system as the M3A1, as well as a better folding stock system.
When the forward assist was first put on the M16 (that WAS an Army request), one Ordnance officer told me it was a "jam maker". He wanted a solid bolt handle ("that I can kick with my boot" to eject a bad round), but by that time the AR-15 design was pretty well "set in concrete" and he lost the battle. He felt that if a cartridge was dirty or bent, it should come out, not be forced in.
Jim
The ejection port cover was not put on the AR-15 because the Army wanted it; it was on both the AR-10 and AR-15 from day one. I handled AR-10's and AR-15's with the old "upper trigger" and they had port covers.
To me, the main advantage of the AR-18 was the bolt riding on rods, like the M3/M3A1 SMG. While the rifle still used a port cover, the rod system made dirt and garbage in the system pretty much irrelevant as there was plenty of room for it. The takedown system, though, needed the same kind of operating spring capture system as the M3A1, as well as a better folding stock system.
When the forward assist was first put on the M16 (that WAS an Army request), one Ordnance officer told me it was a "jam maker". He wanted a solid bolt handle ("that I can kick with my boot" to eject a bad round), but by that time the AR-15 design was pretty well "set in concrete" and he lost the battle. He felt that if a cartridge was dirty or bent, it should come out, not be forced in.
Jim
Dixie Gunsmithing
Moderator Emeritus
Jim, they mention the MAS about the patents, but I didn't notice a date.
The AR-18, did have a funny takedown, in that the rods and springs had to be caught, and let out slowly, if I recall. The patent drawings don't show this well.
The rods would make a big difference, along with the bolt having bearing points at the frame, and not full contact. One would need to keep the rods oiled, though. You can tell a lot of thought went into it about dirt.
I always said, that when they saw the ejection port cover, they should have questioned them about why it was there. I never did agree with the outcome on the AR-15 / M-16, but that's just me.
One thing I noticed more, is the full auto trip changing, and the disconnector being moved. The AR-15 was simple in this regard, and I think they might ought to have stuck with that. It seems they wanted to redesign it all. The bolt won't work with the old, though.
The AR-18, did have a funny takedown, in that the rods and springs had to be caught, and let out slowly, if I recall. The patent drawings don't show this well.
The rods would make a big difference, along with the bolt having bearing points at the frame, and not full contact. One would need to keep the rods oiled, though. You can tell a lot of thought went into it about dirt.
I always said, that when they saw the ejection port cover, they should have questioned them about why it was there. I never did agree with the outcome on the AR-15 / M-16, but that's just me.
One thing I noticed more, is the full auto trip changing, and the disconnector being moved. The AR-15 was simple in this regard, and I think they might ought to have stuck with that. It seems they wanted to redesign it all. The bolt won't work with the old, though.
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Another advantage of the AR-18 (not "M18", it was never adopted by the U.S.) was that it could be manufactured in any country that had simple machining and stamping facilities, rather than having to be machined from forgings on high precision equipment. That meant it was not only cheaper to make in the U.S., but allied countries could buy a license and make their own rather than having the U.S. provide them, a considerable savings in foreign military aid.
The problem was that both the M14 and the M16 were driven by politics rather than a matter of selecting the best rifle. When U.S. Marines stormed ashore in Lebanon in 1958, they were met, not by gunfire, but by women in bikinis. The U.S. was further the butt of jokes because the troops carried WWII M1 rifles, when just about everybody in the Middle East had an AK-47. So it became a matter of national pride to field the M14 and move on to a better selective fire weapon as soon as possible.
That drove the need for a light automatic rifle, and the AR-10 was the only game in town. Meanwhile, the Army was playing with small caliber ammo, and thought a scaled down AR-10 would be the best of both worlds.
There is a lot more to the story. For those interested, I recommend "The Black Rifle" by Blake Stevens and Ed Ezell.
Jim
The problem was that both the M14 and the M16 were driven by politics rather than a matter of selecting the best rifle. When U.S. Marines stormed ashore in Lebanon in 1958, they were met, not by gunfire, but by women in bikinis. The U.S. was further the butt of jokes because the troops carried WWII M1 rifles, when just about everybody in the Middle East had an AK-47. So it became a matter of national pride to field the M14 and move on to a better selective fire weapon as soon as possible.
That drove the need for a light automatic rifle, and the AR-10 was the only game in town. Meanwhile, the Army was playing with small caliber ammo, and thought a scaled down AR-10 would be the best of both worlds.
There is a lot more to the story. For those interested, I recommend "The Black Rifle" by Blake Stevens and Ed Ezell.
Jim
The image posted is just a rough idea of the operation. Im not saying it has advantages over the existing gas/delayed blowback operations but thought it could be simplified and compacted. I would imagine gas/residue to foul up the receiver but this could be sorted out if the cam groove was redesigned to delay the opening as well as the piston head slightly angled/channeled to divert the gas out the ejection port. Also when firing, the locking lugs could shut off the gas to the piston head with the remaining gas in the barrel to operate the reloading of the weapon. For extra reliability, it would depend on the ammo cartridges used.
Gunplummer
New member
Now I am curious. Someone stated that the Army M-16's always had the forward assist. We redid hundreds (Maybe thousands) of uppers over to the A-1 model. Most as I remember were H&R's, there may have been some General Motors lowers, I don't remember for sure. I do remember the H&R's because of the lousy fit between the upper and lower receiver.
The Army never had an M16. First buy for the Army was DA-11-199-AMC-508 in Nov 1963, $13,500,000 for 104,000 rifles:
85,000 with bolt assist designated XM16E1 for the Army and Marines, and 19,000 called the M16 with no bolt assist for the Air Force.
XM16E1's were first issued in Apr 1964.
In Oct 1964, the original order was increased by 33,500 M16's for the Air Force, 240 M16's for the Navy, and 82 M16's for the Coast Guard.
In Jul 1965 the Air Force ordered an additional 36,682 M16's.
Second buy for the Army was DAAF03-66-C-0018 in Jun 1966, which increased the original XM16E1 order to 201,045 rifles.
The XM16E1 was officially classified as "US Rifle, 5.56mm, M16A1" in Feb 1967.
The only M16's were the early Air Force, Navy, and Coast Guard guns with no bolt assist.
Were you working on Air Force guns?
85,000 with bolt assist designated XM16E1 for the Army and Marines, and 19,000 called the M16 with no bolt assist for the Air Force.
XM16E1's were first issued in Apr 1964.
In Oct 1964, the original order was increased by 33,500 M16's for the Air Force, 240 M16's for the Navy, and 82 M16's for the Coast Guard.
In Jul 1965 the Air Force ordered an additional 36,682 M16's.
Second buy for the Army was DAAF03-66-C-0018 in Jun 1966, which increased the original XM16E1 order to 201,045 rifles.
The XM16E1 was officially classified as "US Rifle, 5.56mm, M16A1" in Feb 1967.
The only M16's were the early Air Force, Navy, and Coast Guard guns with no bolt assist.
Were you working on Air Force guns?
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Very interesting, but let's get back to the OP's idea. Here is why it won't work.
Gas at the case mouth is under high pressure. Given an exit, it moves very fast. If it can get past the case mouth into the grooves you visualize in the chamber and strike the bolt carrier, the latter part will move backward at very high speed and unlock the bolt before chamber pressure drops to safe levels.
The result will be an unsupported case at an internal pressure close to maximum chamber pressure. The bolt carrier and bolt will be blown back at high speed and damage themselves and the receiver. Further, the case will let go, the hot gas will escape and continue to expand, blowing the receiver apart.
There is a reason why designers of automatic rifles must make sure the pressure drops before the bolt opens.
Of course, you won't take my word for it, pointing out, correctly, that I have not tried your idea. My response is that you can try it yourself at small cost. A couple of thousand dollars should get you a mockup. But don't make the common mistake of thinking that because something works in a nice drawing, it will work in the real world. Drawings don't operate at 50,000 psi!
Jim
Gas at the case mouth is under high pressure. Given an exit, it moves very fast. If it can get past the case mouth into the grooves you visualize in the chamber and strike the bolt carrier, the latter part will move backward at very high speed and unlock the bolt before chamber pressure drops to safe levels.
The result will be an unsupported case at an internal pressure close to maximum chamber pressure. The bolt carrier and bolt will be blown back at high speed and damage themselves and the receiver. Further, the case will let go, the hot gas will escape and continue to expand, blowing the receiver apart.
There is a reason why designers of automatic rifles must make sure the pressure drops before the bolt opens.
Of course, you won't take my word for it, pointing out, correctly, that I have not tried your idea. My response is that you can try it yourself at small cost. A couple of thousand dollars should get you a mockup. But don't make the common mistake of thinking that because something works in a nice drawing, it will work in the real world. Drawings don't operate at 50,000 psi!
Jim
Dixie Gunsmithing
Moderator Emeritus
There has to be an unlocking delay for any action of a large caliber to work, without rupture of the cartridge. This has been done by several means in the past, but it mainly is done by venting the gas over half way down the barrel, so that by the time the gas acts upon the action, the bullet has cleared the muzzle, and the gas pressure drops. Generally, this delayed action is a combination of the gas acting on a piston, and the weight of the action components, including the bolt, and the recoil spring. An impulse is all that is needed to actuate the action, so by the time the gas reaches the piston, it is already about to start dropping off.
The above is why I mentioned the Benelli inertia operated bolt. With it, venting gas isn't needed, but one could use a combination, I would guess. However, you have gas acting on the bolt, via a piston, which is the cartridge itself, so there is no need to divert any gas around it. How this would work with rifle cartridges, I have no idea.
The above is why I mentioned the Benelli inertia operated bolt. With it, venting gas isn't needed, but one could use a combination, I would guess. However, you have gas acting on the bolt, via a piston, which is the cartridge itself, so there is no need to divert any gas around it. How this would work with rifle cartridges, I have no idea.
Dixie Gunsmithing
Moderator Emeritus
James, has anyone tested the Benelli inertia system in a non-recoiling jig, or fouled the stock against anything, to see what happens when it's shot?
I know that without the receiver recoiling reward, and the rear of the bolt momentarily staying stationary, the bolt can't twist its rotary breech lock, more closed, I guess one could say, however, it is still locked. Also, without the recoil, due to the gun being held stationary, there's no force to drive the bolt back, against the weak bolt spring, for cycling. The more I thought of this system, my guess is, that it would fire, and just not cycle, instead of the bolt opening.
I know that without the receiver recoiling reward, and the rear of the bolt momentarily staying stationary, the bolt can't twist its rotary breech lock, more closed, I guess one could say, however, it is still locked. Also, without the recoil, due to the gun being held stationary, there's no force to drive the bolt back, against the weak bolt spring, for cycling. The more I thought of this system, my guess is, that it would fire, and just not cycle, instead of the bolt opening.
I don't know what would happen if the butt of the gun were placed, say, against a tree. But then that is not the way the gun is supposed to be used, so it is like asking what would happen if the barrel of an Auto 5 were clamped in a vise. (The gun wouldn't work, but so what?)
Remember the cycle, though. The recoil drives the gun back while the heavy bolt carrier tries to remain stationary. That compresses the very strong spring between the bolt and the carrier. When the recoil force dissipates, the spring reasserts itself, and throws the carrier to the rear, camming the bolt open and bringing it along for the ride. There is enough force in that heavy spring to complete the carrier/bolt movement to the rear, at which point the return spring works, as in most semi-autos, to return the whole thing to battery.
That heavy spring is the key to the whole thing, but it just doesn't look like it can do all that it does. And for reasons that are not clear, Benelli seldom describes or pictures what actually happens, apparently preferring to keep it something of a mystery. To further complicate things, the inertia operated guns are only part of Benelli's line which also includes conventional gas guns and over/under guns.
Jim
Remember the cycle, though. The recoil drives the gun back while the heavy bolt carrier tries to remain stationary. That compresses the very strong spring between the bolt and the carrier. When the recoil force dissipates, the spring reasserts itself, and throws the carrier to the rear, camming the bolt open and bringing it along for the ride. There is enough force in that heavy spring to complete the carrier/bolt movement to the rear, at which point the return spring works, as in most semi-autos, to return the whole thing to battery.
That heavy spring is the key to the whole thing, but it just doesn't look like it can do all that it does. And for reasons that are not clear, Benelli seldom describes or pictures what actually happens, apparently preferring to keep it something of a mystery. To further complicate things, the inertia operated guns are only part of Benelli's line which also includes conventional gas guns and over/under guns.
Jim
Dixie Gunsmithing
Moderator Emeritus
The problem I see, for the inertia system, would be acceptance by the military, especially if a gun wouldn't cycle if fouled from recoiling. Say if a soldier was laying flat of his back, and the stock of the gun was on the ground. Then, while trying to fire up at his opponent, he would get one shot off, then be done. Of course they should be trained to know this, but I can envision several circumstances where a conventional action would be better. Thus, would the inertia system have any benefit to a rifle, other than sporting?
On the bolt, it's not just the bolt spring that causes it to cycle, but the overcome forward inertia, as by what I have read, the recoil is still happening when the spring expands back, so the weight of the bolt is driven rearward by the recoil too, and since the return spring is weak, the bolt has enough force to cycle it. I bet a recoil reducer would affect the cycling too, over this, since they work on the inertia basis also.
On the bolt, it's not just the bolt spring that causes it to cycle, but the overcome forward inertia, as by what I have read, the recoil is still happening when the spring expands back, so the weight of the bolt is driven rearward by the recoil too, and since the return spring is weak, the bolt has enough force to cycle it. I bet a recoil reducer would affect the cycling too, over this, since they work on the inertia basis also.
The bolt won't be driven back by recoil; it tries to stay where it is. It has to be moved back by an outside force.
For the reasons you state, the Benelli inertial system would probably not be adapted to a military rifle and as far as I know there are no proposals to do so. It might work in a rifle, but so far Benelli has used it only in a pistol (I have one) and shotguns.
The return spring does not need to be very strong; the A5 is an example of a strong recoil spring and a fairly weak return spring. In the Benelli, that small but strong spring inside the bolt really gives the carrier a heckuva kick. (It doesn't take a lot of movement; look at the M1 Carbine, where the piston moves about 1/8 inch, yet that is enough to kick the operating slide and bolt back and extract the case.)
Jim
For the reasons you state, the Benelli inertial system would probably not be adapted to a military rifle and as far as I know there are no proposals to do so. It might work in a rifle, but so far Benelli has used it only in a pistol (I have one) and shotguns.
The return spring does not need to be very strong; the A5 is an example of a strong recoil spring and a fairly weak return spring. In the Benelli, that small but strong spring inside the bolt really gives the carrier a heckuva kick. (It doesn't take a lot of movement; look at the M1 Carbine, where the piston moves about 1/8 inch, yet that is enough to kick the operating slide and bolt back and extract the case.)
Jim
Gunplummer
New member
45 auto----Most were when I was in the Marines, but I hit a lot of these re-works in what I would call "Secondary" military posts later when I was in the Army. It is easy to see when M-16's were reworked. It is amazing what pops up in some out of the way posts. When I was in Germany (Army) a couple of us representing all the different repair sections went around to different warehouses and identified piles of parts that had lost the stock # identification. It was unbelievable what turned up. You have to remember that some branches did not really "Buy" new equipment. I remember when the Army "gave" the Marines their outdated M60 series tanks. I have no idea if it was considered a purchase by the Marines or not. Anyway, even in the late 70's it was not unusual to find plenty of 1911's in units in Europe. I distinctly remember coming across an M-2 .50 made by colt with a 4 digit serial #. It had oval slots in the barrel support, which was odd. Sometimes when they consolidate a couple of units into a smaller one for an area the units leaving "Donate" some of their equipment to make up the new unit. Guess what the old units get rid of?
Since a discussion of the Benelli got started on this thread, here is Benelli's own video showing how the shotgun works. Watch the large spring carefully to see that the return spring does not compress it, but recoil does once the shot is fired. Then when the recoil force dissipates, the heavy spring re-asserts itself and drives the bolt carrier back, a cam turning and unlocking the rotary bolt head.
https://www.youtube.com/watch?v=2UOSB8mwwlQ
Jim
https://www.youtube.com/watch?v=2UOSB8mwwlQ
Jim
Dixie Gunsmithing
Moderator Emeritus
Jim,
It shows what I've spoken of and read. The inertia spring action, in the bolt, happens for only part of the recoil cycle. When the spring uncoils, it starts the bolt rearward, but the recoil is also going in that direction too, which is countering to the bolt, however, the recoil speed is slowing down, where it will soon stop. The speed the bolt travels overcomes this, due to the recoil slowing down and the springs kick, so the slowing recoil helps it along, and when the gun slows to a stop, on the shoulder, the gun reverses direction, due to the shoulder, and goes forward again, increasing the speed the bolt has going back, until it goes as far as it can, then cycles with the bolt follower spring, (or stays back, due to no new round to release it). The bolt may reach its full rearward stroke, before the shoulder stops the gun, and the muscles cause it to go forward again. That I do not know, and it's not shown. Either way would work.
The cycle is similar to a cue ball, sitting stationary, which is driven against the rail of a pool table, over the sudden movement of the table shifting under it, where the cue ball would then change direction, after it meets and compresses the rail, which sends it backwards. However, in this case, the table would be moving, (recoiling), in the same direction as the reversed ball, which wouldn't work well, unless the tables motion had the brakes applied to it, (the shooters shoulder), slowing it down. It wouldn't work at all, though, if not for the recoil, (or moving table), to set it all in motion.
It shows what I've spoken of and read. The inertia spring action, in the bolt, happens for only part of the recoil cycle. When the spring uncoils, it starts the bolt rearward, but the recoil is also going in that direction too, which is countering to the bolt, however, the recoil speed is slowing down, where it will soon stop. The speed the bolt travels overcomes this, due to the recoil slowing down and the springs kick, so the slowing recoil helps it along, and when the gun slows to a stop, on the shoulder, the gun reverses direction, due to the shoulder, and goes forward again, increasing the speed the bolt has going back, until it goes as far as it can, then cycles with the bolt follower spring, (or stays back, due to no new round to release it). The bolt may reach its full rearward stroke, before the shoulder stops the gun, and the muscles cause it to go forward again. That I do not know, and it's not shown. Either way would work.
The cycle is similar to a cue ball, sitting stationary, which is driven against the rail of a pool table, over the sudden movement of the table shifting under it, where the cue ball would then change direction, after it meets and compresses the rail, which sends it backwards. However, in this case, the table would be moving, (recoiling), in the same direction as the reversed ball, which wouldn't work well, unless the tables motion had the brakes applied to it, (the shooters shoulder), slowing it down. It wouldn't work at all, though, if not for the recoil, (or moving table), to set it all in motion.
I think that bolt carrier* moves back so fast under the impulse of the spring, that the continued movement of the gun in recoil is not significant. Even if it were, it should affect any autoloading shotgun. In a gas gun, the bolt is moving back while there is still recoil force, so it should have the same problem if that problem is there. If the shoulder were padded enough I suppose you could have something equivalent to "limp wristing" but I think a shotgun is heavy enough in itself that that wouldn't happen.
*I am calling the rear part of the bolt the bolt carrier because that is how it acts. The rotating bolt head is really the bolt and the carrier cams it into and out of the locked position, pretty much like an AR-15.
Jim
*I am calling the rear part of the bolt the bolt carrier because that is how it acts. The rotating bolt head is really the bolt and the carrier cams it into and out of the locked position, pretty much like an AR-15.
Jim