1911 magazine pops out when slide cycles

Check the slide to mag catch dimension. To short and the slide will eject the mag.

Try putting the magazine in with the slide back. Maybe you’re not inserting far enough.

guyfromohio said:

Maybe you’re not inserting far enough.

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Or maybe something is preventing it from being fully seated. This LINK may be of some interest in this regard.

One's techniques sometimes have to be adapted to the firearm. I've got a couple pistols where the mag needs to be really slammed in or it doesn't catch and it falls out on the first shot, and a couple of other pistols where using the same technique slamming the mag in causes the slide to release and close.

Firstly, will the problem mags seat with 7 rounds loaded? My shooting stars require force to seat when fully loaded. And I still need to give them a check. (I don't just tap, I check to make sure I can't strip them out.) Prob doesn't apply since it is also happening with the Wilson ...

Secondly, I had an ATI Titan that wouldn't seat my officer mags with flat base plates, though it would seat the factory mags (plastic base) and government mags.

I took a small file to the upper edge of the magazine catch window of the problem mags and removed maybe half a mm. Then they would seat.

It may not have addressed the underlying cause but it made it so all mags functioned reliably, without making changes to the firearm.

My experience may or may not be relevant.

I have a 1911A1 clone (Auto Ordnance (Numrich, West Hurley NY) Thompson branded automatic pistol).
The two aftermarket USA mags that came with it functioned OK. A Colt 1911A1 stainless magazine worked OK.
But two generic military style magazines latched high and only with the slide locked open, and did not work well, until I cut their mag catch notches to the same height as the magazines that did work. I suspect those generic military style magazines were clones made with catch notches intended to be fitted to the individual gun (allowing for wear on old 1911s).

In the opening post OP, the magazine shipped with the gun worked OK, but the gun did not work with Chip McCormick or Wilson magazines.
I suspect that OP's Chip McCormick or Wilson magazines are made to standard 1911 specs, like I suspect my Colt 1911A1 stainless magazine was made to standard 1911 spex.

So I suspect the magazine catch of the OP's gun is the problem and the magazine shipped with the gun was fitted to work. If the refitting was done well, it would not be detectable. If changing the magazine catch to a standard fixes the problem with the other magazines, the original magazine shipped with the gun may or may not work.

Carl N. Brown said:

In the opening post OP, . . . but the gun did not work with Chip McCormick . . . magazines.

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FWIW, McCormick mags sit in the wag well slightly higher than most other magazines. I've encountered pistols in which the right side of these mag tubes ahead of the feed lips would make solid contact with the underside of the slide and prevent not only full seating on a closed slide but would also prevent an open slide from closing. A picture of this is at the bottom of the post I linked to above.

As everyone has noted, there are a number of possible causes related to the geometry of the pistol in terms of location of the mag catch hole in the frame, the location of the mag catch shelf that interfaces with the slot on the magazine, the location of the mag catch slot on the magazine, the possible lack of clearance provided by the frame slot into which the mag base plate fits, as well as possible contact between the magazine and the ejector. Figuring out which of these possibilities is the culprit is the OP's challenge.

^ When I bought a new CZ factory magazine for my CZ52 pistol, I had to do some fitting to get it to match my other two magazines that came with the pistol and its issued holster.

Eli Whitney must spin in his grave at stories of arms' parts made outside the parameters of universal interchangeability within model.

Carl N. Brown said:

Eli Whitney must spin in his grave at stories of arms' parts made outside the parameters of universal interchangeability within model.

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Possibly, but even Eli knew the debil which is "tolerancing."

You can only machine something to only a certain amount of accuracy. It will be plus or minus some amount based on the accuracy of your measuring tools. That tolerance can be deadlined to zero at one side or the other, or in the center. So, for example +0/-0.0015; ±0.00075; or +0.0015/-0--each of those is a very different tolerance despite all of them being 15/10,000ths.

Now, that's simple enough for one part.

When it's two parts, they each have a tolerance, and then they have a tolerance to each other. So, there's three tolerance values at play. This is why the Technical Data Package is more than a dimensioned parts drawing

In this specific case, as a guess, the latch point on the magazine catch is a fraction too "tall." I'll suspect that the Mec-Gar mag has its catch hole a skosh high, too (and may have a slightly 'weaker' spring rate, too).

I would try a different magazine, and fully loaded with dummies/snap caps to make sure the magazine is seating. But, I have the luxury of a huge pile of 1911 magazines to test through, and a pile of snap caps, too. Mind, I have more than one spare mag catch, too--which would be my other test.

OP could try taking the slide off and seating the magazines available, and taking some measurements, to best of ability, of how far the mags are coming out of the frame.

I'm very disinclined to suggest filing on magazines rather than the catch. If a magazine is enough out of spec to need filing, it really ought to be binned.

With the slide locked open, insert a magazine loaded with dummy rounds if you have them. Then see if it's hitting the bottom of the ejector with the round or magazine lip. If so the mag is setting to high. Also if the magazine has a butt plate these can limit how far the mag is inserted.