Longer buffer tube = less felt recoil?

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May 20, 2014
Hi, seeing the AA-12 in action, i just realized this; what if the AR-platform has a longer Buffer tube?

Notice that the telescopic collapisble stock of the M4 and variants? What if it was now not collapsible, and the buffer tube is extended to that of the longest solid stock possible; in which the bolt is shortened and it has more space to recede in to, Would that greatly lessen the recoil? This idea was taken from the AA-12, wthout the API-Blowback system.


Supposed that we get this Bad News Sniper Rifle? : Norreen ULR .338 Lapua Magnum, would it have less recoil?

if it was rigged fully auto: https://www.youtube.com/watch?v=WUwRFxn-4N8

- What is it's cyclic rate without the buffer tube extension?
- What is the cyclic rate of the new one that has the buffer tube extension?
- Can it at least reach 600 RPM?
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Even though the M4 tube is shorter than a standard rifle tube, isn't the distance the buffer travels in that tube about the same?

If so, then a longer tube gains a longer buffer and a different spring to fit that buffer? Just like converting an AR with an M4 stock to an AR with an A1 or A2 stock, where the rifle buffer is longer than an M4 buffer.

So, if the travel of the buffer is the same, then the only thing a theoretical longer than standard rifle buffer tube would offer is the use of a longer than standard rifle buffer? Which could be heavier to match caliber needs, I suppose.

I really don't know, I'm just thinking aloud.
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You can add more weight to the buffer and slow the whole process down. Or put a stiffer spring in it but that creates issues of it's own. But, bigger rounds are going to create more recoil and short of making a longer bolt carrier to travel in the longer tube, you are not going to be able to stop all of the recoil. A longer tube creates issues with length of pull. kwg
No, the extended buffer tube and the shortened bolt would increase the space where the bolt could recede to. I had this idea with the AA-12.
The weight of the buffer controls the cyclic rate, along with port location. Bigger rounds feed incrementally slower, too.

The bigger issue is that there are a lot of what-if's based on a magnum round in a sniper platform firing full auto - which it would never do. It's a one shot at a time sniper, not a full auto medium machine gun. If it was truly meant to fire in the full auto role it would look a lot more like an M60, and nobody would expect anything precision in the way it shot jumping around in the shooter's hands. While a .50 BMG is on record as having been used as a sniper gun, it's was an exceptional situation and fired semi-auto on a tripod with T&E, sighted in and even having placed shots prior to it's use.

Using a .338 full auto sniper would last about two magazines - about what a team takes on a mission to place precise shots a thousand yards out. The spotter carries the full auto M16 for close support, and if they need it, they weren't doing their job very well.

Basically, the questions imply doing something that a sniper wouldn't do to a precision rifle, in a role it's not suited for. When the military is confronted with a situation like that, they task the crew served weapons to git er done, not abuse something never intended to do it.
The thing about the 'constant recoil' action spring in the AA-12 (and it's progenitor the Daewoo USAS-12) is not just that the spring is longer, it's much longer.

You can see it extending from the buttstock in this pic of a disassembled USAS. When assembled the spring only compresses about 3.5 inches (equal to the rear of the magazine.)

It's also an awkward, freakin' heavy beast, you wouldn't want to hump one around all day.
I don't know, i saw in this video that the bolt of the AA-12 has a lot of space to recede.


Also, the circumstances of whether it is going to be really used. Or nobody will make or use a full auto sniper rifle is not exactly relevant, it's superfluous. What is relevant is the physics, the engineering.
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Not sure of what you are worried about. There is so little recoil on an AR as they are now that I don't see any real gain to be had. You can put an AR stock against your chin and fire it without any ill effects.

It sounds like a solution to a problem that doesn't exist.
Bolt carrier travel is still going to be restricted by the upper receiver with charging handle installed due to the gas key.
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Supposed that we fixed that, just allow the shortened bolt to recede further inward the extended buffer tube.
Don't see how a shortened bolt, carrier or even buffer would fix that. You would either have to remove the gas key (or piston tab/key if you decided to go piston) on the carrier or lengthen the trough it follows in the upper receiver/charging handle by lengthening the upper receiver itself, which turns it into something of a creation unto itself. I suppose that you *could* go the piston route and move the piston tab/key further forward on the carrier thus allowing more room to travel, but how much more room is there to move it forward? An inch, mabye an inch and a half?
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Yes, lengthen the recess for the piston.

Shapes problem aside, because engineering would fix that. Physics, if the space for the bolt-carrier to receed in extends for 100% more, what will be it's effect upon the cyclic rate and felt recoil.
It very much does make a difference how the weapon is used, but reality aside, we can stick to the physics.

A .338 AR10 with long recoil buffer, leaving aside the genetically selected operator who could shoot it (not me,) would involve allowing the buffer and bolt carrier to slide another what - 12 inches - during the operating cycle. It would then have to return that extra 12 inches to load the next cartridge, which means that it would have to still have the kinectic energy necessary to strip the cartridge from the magazine and chamber the same with enough force to reliably do it every time.

Adding the extra twelve inches of travel one way, it's doubled back in the loading cycle. That's another 24 inches of buffer and bolt carrier travel with it's related friction that reduces the speed and retained energy to reload the weapons. So, we have to add that to the overall impetus given it at the start - making initial impulse even higher, to overcome the added travel and friction.

That means the port would be even closer to the chamber on the AR10, and recoil as perceived by the shooter would be higher, not lower. More pressure for the bolt carrier to rebound and travel would be required.

So, it won't work. To get it to function, recoil would go UP, not down. Note that the Stoner design team could have had the buffer inside the spring to add the collapsed length of the present design added to the travel and making it a longer stroke. They were originally working with the .308 cartridge and it wasn't considered valid in the final design.
Instead of worrying the length of the extension tube, I would be figuring out how to install a LimbSaver recoil pad.
ANYTHING in .338 Lapua is going to let you know it is going off,,,
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