Premature slide lock

[jakjakman]

I've was at the range today trying out some new mags and ran into some problems. I'm also shooting a newer 1911 so the round count so far is pretty low.

The problem I was seeing is that after tac-loading a full mag (McCormick power mag) into the gun with a round in the chamber, sometimes the slide would lock back after firing the first round. After looking at the open slide, this is what I would see:

http://i36.photobucket.com/albums/e5/jakjakman/xIMG_0806.jpg

It seems that during the recoil the round will slip forward in the mag and somehow slightly trip the slide release to keep it open. Looking at the slide release I could see that it had just barely caught on the slide to lock it back. This happened several times with brand new McCormick magazines, so I'm guessing this is something up with the gun. Any ideas on how this problem should be addressed?

[Lincoln7]

I've shortened the length of the slide stop protrusion with a file with success. This prevents the bullet tip of the next round in the magazine from lifting the slide stop prematurely. Also, if the magazine spring is weak, rounds can be shook from the magazine during recoil and then contact the slide stop. Stronger mag springs can help this. If the recoil is too harsh (from a worn recoil spring) it can contribute. But worn springs don't sound like the issue with your new equipment.

[az doug]

+1.

Also, profile of the projectile can have a lot to do with it. Trimming the inside of the slide stop should resolve the issue, regardless of projectile profile. Some manufacturers such as Kimber are aware of the issue and if you call them they will send you a trimmed slide stop. Rather than correct the problem they seem to play the odds that the average owner will never have this issue.

[wilco423]

What magazines had you been using previously? If I understand correctly, this is the first time you've used the CM mags, and the other ones worked okay. Some (maybe most) 1911s prefer one type of mag over another, particularly when it comes to premature or no lock back. If the mags you had been using fit your criteria for use otherwise, might be a good idea to just go with those.

I bought 8 CM 8 round Power and Power+ mags after buying my 1911 (a used SA TRP), only to find they had the same issues as yours. Rather than get rid of the mags (just didn't feel like returning or selling 'em), I tried a 10-8 slide stop. It worked in my gun, and I like the aggressive profile of the release lever. It's not 100% with Tripp Cobra mags on locking back on an empty, but works well with the 3 types of CM mags I have.

I guess what I'm saying is, if you only got one or two CM mags, you might just try some other ones out. This is what I should have done in the first place. If you were like me and bought $180 worth of mags that don't work in your gun :mad:, try a good slide stop (preferably fitted by a good gunsmith) and see what happens.

ETA: Re-profiling your existing slide stop is a good, no cost, option. You should be able to see where the rounds are contacting the lobe on the stop and remove a little bit of metal at a time. I went with the 10-8 stop because: one, I apparently like to spend money, and two, I wanted to try that stop to see if it would help with manipulations, which it did. Check out 1911forum for good info on gunsmithing and troubleshooting.

[jakjakman]

What magazines had you been using previously? If I understand correctly, this is the first time you've used the CM mags, and the other ones worked okay. Some (maybe most) 1911s prefer one type of mag over another, particularly when it comes to premature or no lock back. If the mags you had been using fit your criteria for use otherwise, might be a good idea to just go with those.


Before I just used the OEM mags that came with the gun and some 10rnd Wilson mags. However, when shooting with them, I don't think I tried shooting with a full mag +1 in the chamber, so I don't think I had the right conditions to produce the erroneousness slide lock. Lucky for me Mars Armament is about 20 min away so I'll see if Steve can file a bit of the slide release off. The 10-8 slide releases look nice, but I'd like to keep the original so the finishes match. ;)

[wilco423]

Before I just used the OEM mags that came with the gun and some 10rnd Wilson mags. However, when shooting with them, I don't think I tried shooting with a full mag +1 in the chamber, so I don't think I had the right conditions to produce the erroneousness slide lock. Lucky for me Mars Armament is about 20 min away so I'll see if Steve can file a bit of the slide release off. The 10-8 slide releases look nice, but I'd like to keep the original so the finishes match. ;)

Roger that. I'd love to have a smith of that caliber in my area! I'm sure you won't be disappointed. Let us know how it turns out.

[Dienekes]

Another reason that you might get premature lockback is if the slide stop will move upwards too easily under recoil. I dimpled the rear face of an SA slide stop some years ago so the spring-loaded detent held it down slightly better, but it would still rise properly when the follower engaged the inner shelf. Problem cured in that case.

I'd rather have the slide stop fail to engage at all than to engage too soon/too often.

[Gunzilla]

Had the same issue using American Eagle 230 gr ball ammo in my new DW Valor. The bullet profile was different than the other brands I shot that day and the problem didn't repeat with different ammo.

It may be as easy as ammo selection, otherwise I'd take Lincoln's advice and take a very small amount of material from the cam and retest, repeat until the problem goes away. It should be easy to find the 'high' spot that is catching, just look for the copper left behind as the bullet went past the cam and use a fine file or emery cloth to remove excess material. (I used 230 grit emery cloth)

Good luck