I've been able to clear a little off my plate today, so I'll go ahead with the explanation of all the factors at work whenever the radius of a simple firing pin stop is changed...and how they affect the recoil cycle of the 1911 pistol.
In the interest of a smoother flow, I ask that comments and questions be held until I've finsihed. I need to split this up into two or three separate segments to keep it from dragging on for too long. I've found that people who are reading an overly long text tend to skim over a lot of it...or skip it outright...the instant that they find something that they don't understand or disagree with. I won't argue these points. I've already done that too much, and I don't have to time. Instead, I'll describe the function and the physics involved, and let everytone decide for themselves whether they want to accept it or not.
First...a few things that we need to clarify and accept as simple physical and mechanical fact.
Force forward=force backward. Always. If X units of force is applied, it applies in all directions. Thus...if X units of force is brought to bear on a closed system, it's applied backward and forward in equal measure. This is known as a "vectored" force. That is...it has magnitude and direction.
Recoil is nothing more than backward acceleration in response to a force applied to a closed system in which at least one side of the system is moveable. Even if the recoil impulse doesn't produce movement, it still occurs. The reason that no movement is seen on the reaction side is because the force wasn't large enough to overcome the level of resistance offered by the reaction side. A 500-pound .223 caliber rifle may be used as a demonstration. Actgion and reaction occur, but you can't detect reaction due to the mass and the force applied to that mass.
Recoil only occurs when acceleration is applied. Once the acelerative force is removed, there is no further acceleration...and hence, no more recoil. What we perceive as recoil is mostly momentum that was conserved while the accelerating force was on the system. The actual recoil impulse is over so quickly that we scarcely have time to detect it.
When the bullet exits, the force is removed from the system, and neither bullet nor breechblock can accelerate further. All movement after the force has been removed is due to conserved momentum. For both sides, all they can do is decelerate due to outside forces that they encounter.
Any outside force that is imposed on the system while under an accelerating force will affect the rate of acceleration, and the remaining momentum that is conserved during the acceleration. Anything that has the opportunity to to affect the object's motion will do just that. Once momentum is lost, it can never be regained unless a "new" force is applied.
Force makes things move. Momentum keeps them moving. Force robs moving objects of speed and momentum.
Recoil operated pistols and straight blowback pistols are both recoil operated. Blowback is misleading. The only real difference is in the mechanical method of delaying the breech opening until the bullet has exited, and pressure drops to a safe level.
In the short recoil system, the bullet is the main delaying factor. Go back to force forward=force backward. The barrel imposes a frictional resistance to the bullet. Whatever friction the barrel offers to the bullet, the bullet offers to the barrel. The barrel moves backward while the bullet is moving forward...each one resisting the other. All other delaying forces...recoil spring...mainspring...slide mass...barrel mass...and slide to frame friction are secondary to the bullet's influence.
Small changes to the outside forces resisting the slide cause large changes to the slide's rearward travel, and the earlier in the slide's acceleration the decelerating force is applied, the larger its effect on the slide's rate of acceleration and its conserved momentum.
In an autopistol...regardless of the design...we feel very little recoil, if any, as a result of the internal ballistic event...or the "explosion" of the powder. The gun is comprised of the barrel and the breechblock...the slide. The frame is essentially a gun mount with no solid connection to the gun. None of the actual recoil impulse is transmitted directly to the frame that way it is in a fixed-breech revolver or bolt-action rifle.
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