Try a Wilson Combat mag.

First time shooting a 1911? Just asking because I’ve seen a lot of guys grip be the issue. They’re riding the slide lock with their palm swell and it pushes up ever so slightly and it will lock the slide back. Since it’s pretty much new the spring and extent might need a little breaking in too.

It's my FIL's. I'll check and see if that might be it. Thanks for the tip.

I've shot 1911s a long time. I have a Colt and an old WW2 Remington Rand that I love to shoot

Try a Wilson Combat mag.

I thought you had posted about 1911's in the past which is why I asked. Sorry my phone auto corrected me, I meant spring and detent.

Dumb question - is the 7 round or 8 round more likely to be reliable? Or doesn't matter? Does the 8-round stick out past the grip more, or same?

If both of those answers are the same, why do they sell 7 rounders? Just a nod to Mr. John Browning?

No idea why some prefer 7 rounders.

There are small differences in geometry of mags and also feed ramps.

I tested a bunch of mags long ago. For the last fifteen years or so I have carried the Wilson ETM 8 round mags every day and trust my life to them working correctly.

Tripp Cobra mags and Chip McCormick are others to try, but try the Wilson first.

Cool

This is an Ultra Carry Kimber - do they use regular 1911 mags? WC ETM says they're compatible with Commander, so I assume it's good?

Glad you weighed in KR, I just edited mine after looking at Kimber’s webpage.

So any mag that will fit an officer size 1911 should be good?

Call me crazy but this and WC mags

It’s the only firearm I grease

Yes.

This is almost always due to the nose of the bullet bumping the inside lug of the slide stop on feeding. Removing material from the rear corner of the slide stop internal lug and/or shooting more pointed bullets will resolve this issue.