I took my first tactical shooting class last week and other than my Steyr USR everyone had ARs. About 5 out of 10 of them had some kind of jam/double feed. (I was kind of enjoying it) Not to brag, but the Steyr was flawless. I was told that most AR failures are magazine related. OK fine, so my question is how long are AUG mags lasting before needing replacement? Is there a weakness to beware of ?