Get the 30 round milspec mags. They have a number stamped on them to identify them as such. (33710 above the date code). The Okay Mags have it, the NHMTG mags have it, and some others like Cooper. If they turn out to have weak springs replace the springs and followers. I like the green followers.
I have a slew of 20 round Colt Mags. They don't have the number but work very well.