Slide occasionally locks back before empty

[TracerRound]

Hey guys, any idea why my SA 1911 slide locks back occasionally before the mag goes empty. Doesn't happen all the time just periodically.
Thanks

[Pappy]

Hey guys, any idea why my SA 1911 slide locks back occasionally before the mag goes empty. Doesn't happen all the time just periodically.
Thanks

Weak mag spring.
Under recoil, top round in mag moves forward and bullet nose nudges the slidestop button.
What mag are you using?? Pappy

[John]

Does it happen with the first few rounds? The last couple of them? Any round in general?

If it happens with the last couple of rounds, Pappy's advise is correct, your magazine spring is weak and allows the last couple of rounds to move forward, thus touching the slide stop and causing the slide to lock back.

If it happens with any round in the magazine then your slide stop is probably not properly fitted to the gun. Remove the slide and insert an empty magazine. See where the magazine follower touches the slide stop? Now remove the empty mag and insert a loaded one. Notice the area of the slide stop that comes close to the round's nose? You may file that down a little bit, so that it doesn't contact the rounds, but not too much that it will stop getting popped up by the follower (that's why I told you to use an empty mag first).

[TracerRound]

It did happen with the last couple rounds in the mag. Its a 10 round CM shooting star.

[John]

Well, I would contact McCormick and ask them for a new magazine spring. What happens is that the spring is not putting enough upwards pressure on the last couple of rounds to keep them in place. Due to the gun's recoil the rounds move forward and as they move up they touch the slide stop thus locking your slide back prematurely.