Sooooo I picked up a troy mag today to try out this weekend and include in my overall experiment with mag reliability... After looking at the feed lips on these other mags I think the traits that fair the best in overall function are the lower front feed area of the mag and the internal gentle push of the bullet side of the round towards the center of the magazine. The Surefire 60 round, colt 20 round and the PMAGS work all the time.... the usa mag works as long as the recoil doesn't dislodge the bottom plate and release the mag spring and whatever is left in the mag onto the ground... Anyways here is some pics to show what I am talking about...