M1911 Locked breech/Short Recoil basic function
Caliber .45 Auto firing a 230 grain bullet at 830 fps:
Bang! Assuming a condition of zero headspace, both bullet and slide start to accelerate at the same instant. The slide grabs the barrel upper lugs and hauls the barrel backward with it.
At nominally 1/10th inch of rearward slide/barrel movement, the bullet exits, and pressure quickly vents through the muzzle and drops to atmospheric.
At the point of bullet exit, the barrel remains vertically and horizontally engaged with the slide, and the link has just started to tug on the barrel.
Slide and barrel continue rearward as the link pulls the barrel down. At nominally 2/10ths of an inch of rearward travel, the barrel upper lugs are clear of the slide’s lugs, and the slide and barrel start to separate as the breech opens and the slide is now free to continue its rearward journey.
The barrel continues to move rearward from its momentum while the link continues to pull it downward. At 1/4th inch of rearward travel, the link has taken the barrel as far as it can. The rear of the lower barrel lug strikes the frame vertical impact surface and stops all rearward movement. Ideally, the barrel should be approximately .003 inch off the frame bed at the point of vertical impact surface contact, with .012-.015 inch of clearance between the top of the barrel hood and the first slide lug, and gravity takes the barrel to the frame bed.
The “recoil” spring’s effect on this sequence is negligible, and it has no effect on barrel unlock timing.
As you can see by this video 1911 Tuner and I shot, in a controlled environment, not only did the lack of recoil spring not affect the lock up of the gun, it also did not cause any damage. This was not the first time this experiment has been done with this very pistol, it has been repeated dozens of times. All cases were recovered and inspected for bulges, which there were none.