Sorry if I have Patents on the mind, but there are other more effective ways of lessening the effect of recoil on the shooter and on the next shot as in a full-auto weapon. Let me go into a bit of what I understand, right or wrong, about recoil forces.
Using the AK-47 as an example:
First, the detonation of the cartridge causes the rifle to move rearward inline with the bore of the rifle.
Second, Expanding gas in the gas piston cause the bolt carrier to recoil to the rear the resulting force above the centerline of the bore pushing the rifle forward and down.
The third principle force is that of the bolt carrier assembly slamming against the rear of the receiver on about the same line as the second force but sharper than even the first force. This tends to cause the muzzle to rise. This third force is combined with moments of rising pressure and falling pressure as the carrier assembly first compresses and then is accelerated byt he operating spring.
Fourth, the bolt carrier assembly slams into the receiver assembly causing the same motion as the second force but much sharper.
These forces don't cancel each other out ever. The same force is always transfered to the shooter on rifles of like caliber. That is the force of the bullet and propellant gasses exiting the rifle from the muzzle. Muzzle breaks can counteract this by negating the effect of the propellant gasses. Generally this is about 20-50% of the recoil. (Yes, they are lighter but move MUCH quicker). Some muzzle brakes can direct these gasses rearward and make up for some of the bullets recoil.
Back to the subject at hand. I think the Germans came up with the principle of constant recoiling for a firearm. IIRC, this was for one of their assault rifles. The principle goes that the bolt carrier assembly doesn't stop at the rear but is gradually slowed and then pushed forward by the spring. This evens out the pressure curve significantly on an open-bolt gun as the gun fires on the forward stop of the carrier travel. This completely eliminates the third and fourth sharp recoil forces and result in a weapon that is very easy to control.
I'm not quite sure why, but the M-16 which has enough space to utilize this system, instead went with a bulky and marginally effective series of weights to attenuate the third and fourth forces. Combine this with a theoretical in-line recoil (but most people mount the rifle too high on their shoulder to realize this) and you have eliminated muzzle-rise.
Why not eliminate the peaks and valleys in the pressure curve instead of just blunting them. Stoner went a long way toward this, but not far enough. We're left with a vibrating bullet hose. Much better than an undulating, vibrating bullet hose as in the AK-47, but still not the near-steady hose of constant recoiling rifles. Patent #4,502,367 is an interesting read of this relationship. It's 56 pages long. I ordered a copy for $3 from the USPTO. It's worth it.
