I have some experience with the Pmags, both the standard and window models. We (the agency I work for) had heard they were good mags and passed all attempted failure tests in a torture run at Gunsite. So, we decided to try them out.
We have a variety of rifles including personally owned AR's (numerous varieties), Viet-nam era M-16A1's from the Army, new production Colts, model-1 frankenguns using some of the A1 full auto lowers, etc.
We have yet to have a failure with the mags, except when we max them out. I have one mag that will take 31 rounds, not sure why. It is a window mag and I realized something was wrong when the last round went in on the left side of the mag. It was fully maxed out and when I fired the M-16 it provided enough tension on the bolt to prevent it from fully cycling. I had inserted the mag during an exchange so it was chambered. The other mags load to 30 and I haven't had that problem.
We have also found they are 100% on full auto with full length M16-A1's and on our 10 1/2 inch entry guns.
As an instructor and officer who carries a rifle at work (not that we ever really get into shootings) I highly recommend the Pmags. They are the only mags I have never had a failure with (when you don't cram the extra round in). Most of our Colt mags work just fine, but some of our officers still carry Bushmaster mags. They are burm mags. All they are good for is throwing over the burm.
I had a difficult time finding good mags in Iraq and would have loved 10 pmags instead of 10 mix and match old mags. Better mags showed up later, but it still would have been nice to have the Pmags.
