My first range trip with them was very disappointing. I loaded three mags and only got through one without any failures. I was using cheap Monarch brand .223 ammo, but I'd never had issue with it before. The only thing I could think of was that maybe the lacquer on the ammo was hanging up on the sharper feed lips of the aluminum mags and causing the repeated failures to feed.
Today I took the rifle back to the range with two of these aluminum mags, one loaded with M193 and the other loaded with Monarch ammo. I also took a Pmag loaded with Monarch and a steel E-lander mag loaded with Monarch.
I shot out of a Brownells magazine first. I could not get through a V-Tac 1-5 drill without a failure, and had repeated failures to feed every round or couple of rounds until the magazine was empty.
Following the Brownells magazine I immediately loaded the Pmag and shot two 1-5 drills without a single failure of any sort. I dropped that mag and loaded the E-Lander and again fired two 1-5 drills without any failure. Both magazines functioned flawlessly. This eliminated the gun as a potential source of the problem.
I loaded my second Brownells magazine, this one with the M193, and again experienced repeated, continuous failures to feed. I was about halfway through the mag and experiencing a failure to feed after every round fired when I decided to stop.
I've only to date tested 3 of the ten magazines Brownells shipped me, but that's a 30% failure rate already. I'll eventually shoot out of all of them (I do intend to keep them if for no other reason than to practice my failure clearing).
The Brownells aluminum AR15/M16 30 round magazines that I received are made of suck and fail, and I will not recommend anyone purchase them unless they are looking for magazines to deliberately induce failures for training purposes.