hell i have been shooting the hell out of some of my ar-15 with the cheap ammo for some years now. can't say i have had many problems even burning the toxic yugo 7.62 brass and 5.45x39.
some of the brand name ar-15s have gas ports a shade too small to run the cheap stuff which has slower lower pressure powder.
the only cheap stuff that wouldn't run in mine was that one batch of tula 55gr that had the bad powder. i mean really bad powder --LOL!
that batch also was not 100% in my ak which would damn near cycle on just a primer--LOL