I used USGI aluminum magazines professionally (as an Infantryman and cop) for 40 years. When I enlisted in 74 they were 20 round mags. 30 round mags were in the system but no one had them. Never really saw my first issue 30 round aluminum mag until 77 or 78 when they started issuing the ALICE nylon ammo pouches for them. I can remember one lot made by OK (I might be wrong about the manufacturer it was a long time ago, mid 80s) that was recalled because they just plain didn't work. Other then that, if a unit replaced them when they wore out they were just as reliable as PMAGs.
Around 1991 we got some Thermolds, must have been some kind of deal with Canada, they had the maple leaf molded in them. They were crap. If you dropped a loaded one on the ground 8 times out of 10 it would unload itself, spewing live rounds all over the ground. The feed lips were that bad.
If you had bad aluminum magazines it was because your unit was too cheap to replace them before you deployed. I can't imagine going into combat with mags that were beaten up on ranges and with blanks for years but I guess some units did.
The way the military pisses money away and considering all of the non-standard stuff commanders bought off the shelf with RFI money in the early days of the war, if the aluminum magazine had been unsuitable it would have been replaced.
My middle son did tours as an Infantryman in both Iraq and Afghanistan ( he's in Korea now) and reported no problems with any magazines except for M9 mags. In fact when he got a pistol in Iraq, I sent him 5 Beretta made magazines for it because the issue mags were crap (checkmate IRRC).