pblanc said:
The reason is that upon ignition, there is an immediate retrograde force applied to the breech block that initiates muzzle rise during recoil. Even a tiny angular difference in muzzle rise will result in a significant shift in POI
With semi-autos that have a fixed barrel (like most of the .380s, 32s, 25s, and .22s) and revolvers, when the bullet is fired, recoil begins to be transferred immediately to the frame. That rearward movement, which is above the shooter's hand, causes barrel rise (which is directly attached to the frame and the grip in the shooter's hand) causes the whole assembly to rock back in the shooter's hand. The barrel doesn't rise until its rearward movement hits a stop (in the case of the gun, the barrel is attached to the top of a long handle (the grip).
Guns using the Browning Short Recoil Locked Breech design (which includes nearly all other center-fire handguns)
handle recoil differently than fixed barrel semi-autos or revolvers.
The initial force of the recoil pushes the slide and barrel to rear -- and the bullet typically leaves the barrel before the barrel and slide have moved more than 1/10th of an inch to the rear. While ecoil force will be transferred to the frame throughout the barrel/slide movement to the rear, only a small amount of recoil can be transferred to the frame during that 1/10th of an inch of slide/barrel travel (before the bullet leaves the barrel.)
The barrel won't begin to rise until the barrel and slide hit their respective stops on the frame. Then the remaining substantial recoil force will cause the gun to rock back in the shooter's hand. With the Browniing SRLB design, the same recoil force is transferred to the frame as with other designs, but the initial transfer of the recoil is delayed -- generally until after the bullet is gone.
If you doubt this, watch any number of ultra-high-speed videos of Brownign SRLB guns being fired on YouTube. There will be almost no barrel rise visible or measurable until AFTER the bullet is gone. At most handgun distances (maybe up to 50 yards, the biggest difference in pointsof impact will be due to velocity and gravity, not to round-induced barrel rise.