1911 Malfunction

[Bo Bender]

Here’s a new malfunction that I experienced today while practicing  with my wild bunch 1911. Shooting the same gun(Remington R1), same mags(Wilson Combat) and same ammo(230g 5g W231) that has never let me down. Seven rounds in the mags, fire six rounds flawlessly, 6th round goes bang and ejects, slide locks open and seventh round floating around in the breech. I was shooting one handed, white knuckling the grip so my thumb was nowhere near the slide stop, i certainly wasn’t limp wristing it. This happened several times but not until after about 100 rounds, the sun was hot and so was the gun in case that matters. Anyone have any theories on the cause?

Something is allowing that 7th round to pop up as the slide goes back which allows the follower to trip the slide stop. Can it be as simple as the mag lips need readjusting? 
TIA for your help

[El Chapo]

What does "floating around in the breach" mean?  It is not uncommon for 1911s to lock back with one round in the magazine, and for that, you may have to adjust the fit of your slide stop to the magazines you're using if that's happening.  If your feed lips are out of spec, it's also not uncommon for a round to "squirt" out of the top of the magazine sometimes, although that is more common with 9mm magazines than 45.  What exactly is it doing?  If I understand your symptom correctly, it sounds like a feed lip problem to me.  The easiest way to diagnose is to identify the problem magazines and compare feed lip dimensions.

[Bo Bender]

3 hours ago, El Chapo said:

What does "floating around in the breach" mean?  It is not uncommon for 1911s to lock back with one round in the magazine, and for that, you may have to adjust the fit of your slide stop to the magazines you're using if that's happening.  If your feed lips are out of spec, it's also not uncommon for a round to "squirt" out of the top of the magazine sometimes, although that is more common with 9mm magazines than 45.  What exactly is it doing?  If I understand your symptom correctly, it sounds like a feed lip problem to me.  The easiest way to diagnose is to identify the problem magazines and compare feed lip dimensions.

I’m numbering the mags now and will see if I can narrow it down to two or three culprits. It does appear to be mag feed lip issues, the seventh round is popping out of the mag as the slide goes back, once that round clears the mag, the follower can activate the slide stop.

whats your experience with stainless mags, do the lips hold up longer that blued steel? Is there a brand of mag that holds up better, im currently running Wilson combat mags and they have been flawless until now?