I have quite a few USA mag's and have had no problems with them.  In fact I have had more problems with my Colt clips and the more expenseive GI mag's.  I don't get everyones complaints about them.
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You are the lucky one.  Most of what I hear is "bad followers, weak springs, mis formed lips, mag latch is in the wrong place....."  Have two Tec mags from USA....needed to be modified.

USA mags suck!!!

Prior to the PRK ban, I went out and bought a bunch of AR mags.  I bought about a dozen GI mags, a few Thermolds, and a dozen USA mags.  I tried about 8 of the USA mags, and 2 of them wouldn't even fit in the mag well.  Another 3 wouldn't feed even after "adjustment".  I expected to get a few duds, but in reality they are all duds.  I knew the mags were junk, but they were price gouging GI mags at the time.  All said an done I should have bought 2 more GI or Thermold mags rather than a Dozen USA mags.

I would never trust my life to a gun with a USA mag in it!