my 5.56 AR15 doesn't care what you put in it, I have a 30 year old polymer mag that was left loaded for the last 15 years and my gun didn't even hiccup when I fired that junk out of it, USGI, PMAGS, and one low cap mag I bought for hunting all work just fine in mine and it's widely regarded to be one of the lowest quality ARs out there.
my 9mm on the other hand is very picky, it has to have metal form mags to work, Cmags are garbage in it.
ignore my complete lack of capitalization. I still have no problem correcting your grammar.
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Bean counters told me I couldn't fire a man for being in a wheelchair, did it anyway. Ramps are expensive.-Cave Johnson.