I hear these kind of stories all the time, and just shake my head. I started instructing on weapons and tactics, in 1978 and did so the next 18 years. At retirement, I guess I had fired about everything police related, and I don't mean a few rounds. I mean in the thousands of rounds I have fired PERSONALLY, and the thousands & thousands of rounds I have supervised other officers firing, I have witnessed ONE malfunction, and it was due to a dry bolt. A little oil and the AR was up and running with not another hitch.
I have attended 2 week SWAT training schools where the ARs went two weeks with nothing more than oiling at the end of each day. Other depts. may have had malfunctions, but they kept the quite if they did, as I did not see them.
I have owned 2 original Colts, one an A1, and the other an A2 and in the thousands of rounds, thru both, never a malfunction. Four Bushmaster M4s. Same story, and I still have one of those.
The Colt A2 and I slept together in the Red River bottoms of the Oklahoma-Texas Border waitin on marijuana growers, and looking for their "patches". Hot, sweaty, and sandy, but always reliable.
I would question your buddies selection of brand of AR, their maintenance of the their ARs, their magazines for their ARs, and the ammo for their ARs. This is one more fishy story, to say the least.