You can try a 1911 mag too, is should slip right in also.
I polish my mags, get that satin finish off them and then paste wax. They polish up really easy and quick.
This may help but not solve your issue. Squeezing the mag a bit as CJB suggested is probably the next step. You can check that with a caliper to see if it flares out a bit at the feel lips.
Look closely in the mag well for mold left overs or anything that could be cleaned up a bit with some sandpaper.
In Memory of Paul "Dietrich" Stines.
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Cue sound of Head slap.
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