Most people who are into autopistols have at least a working understanding of short recoil operation.
But, is it really recoil that causes the whole thing to function...or is it actually something else? Is ballistic recoil...the recoil generated by firing a cartridge...actually what causes the gun to function, or does recoil only get it started and something else finishes it?
First, a few things to understand.
Recoil is only in play for a very brief instant. Assuming 230 grains at 830 fps and a 5-inch barrel, it takes about 2/1000ths of a second for the bullet to make the 4.2 inch trip through the rifling to the muzzle. During that nearly immeasurble instant, the slide moves 1/10th of an inch. This will vary +/- a couple thousandths depending on several factors, but for our purposes here, 1/10th inch will do.
Once the bullet has broken free, ballistic recoil ends. All forces that set the system in motion are gone. Neither bullet nor slide can accelerate or even maintain their respective velocities that existed at the instant of bullet exit. They can only decelerate.
So...speaking to the slide...everything after that is on the momentum that was generated by that very short time and distance during which it was being accelerated.
And, then the slide hits the impact abutment in the frame and everything stops. The action spring then starts to unload its stored energy and gets the slide moving back toward battery. While the slide is accelerating...because momentum is a function of Mass X Velocity...it's gaining momentum, and momentum is more necessary than the spring in getting the slide back into battery. I proved that once to a guy by removing the little weights from the buffer assembly in his AR15 and firing it. He was curious as to whether he could get it to cycle faster by removing weight from the reciprocating assembly. It failed to go to battery about one time in 3 tries, even though the spring was still fully in play. I put the weights back.
So, would it be more accurate to describe it as "Spring and Momentum Operated" since momentum gets the slide to the impact abutment and spring and momentum get it back into battery?
Or, am I just overthinking this?
But, is it really recoil that causes the whole thing to function...or is it actually something else? Is ballistic recoil...the recoil generated by firing a cartridge...actually what causes the gun to function, or does recoil only get it started and something else finishes it?
First, a few things to understand.
Recoil is only in play for a very brief instant. Assuming 230 grains at 830 fps and a 5-inch barrel, it takes about 2/1000ths of a second for the bullet to make the 4.2 inch trip through the rifling to the muzzle. During that nearly immeasurble instant, the slide moves 1/10th of an inch. This will vary +/- a couple thousandths depending on several factors, but for our purposes here, 1/10th inch will do.
Once the bullet has broken free, ballistic recoil ends. All forces that set the system in motion are gone. Neither bullet nor slide can accelerate or even maintain their respective velocities that existed at the instant of bullet exit. They can only decelerate.
So...speaking to the slide...everything after that is on the momentum that was generated by that very short time and distance during which it was being accelerated.
And, then the slide hits the impact abutment in the frame and everything stops. The action spring then starts to unload its stored energy and gets the slide moving back toward battery. While the slide is accelerating...because momentum is a function of Mass X Velocity...it's gaining momentum, and momentum is more necessary than the spring in getting the slide back into battery. I proved that once to a guy by removing the little weights from the buffer assembly in his AR15 and firing it. He was curious as to whether he could get it to cycle faster by removing weight from the reciprocating assembly. It failed to go to battery about one time in 3 tries, even though the spring was still fully in play. I put the weights back.
So, would it be more accurate to describe it as "Spring and Momentum Operated" since momentum gets the slide to the impact abutment and spring and momentum get it back into battery?
Or, am I just overthinking this?
Last edited: