My experience runs counter to some posting here. I have had issues in several ARs, with ASC mags. I have 10 rounders used in a 204 Ruger, a 6mm WOA, and a 6.8 SPC. All of them bulged, and caused malfunctions. And yes they were the stainless steel varieties. For me PRI mags have been rock solid. I have five 10 rounders, and one 25 rounder, for 6.8 SPC cases, and variants, and have never had a magazine related failure that I can recall. I also have 5.56 versions used for the 204 Ruger, and a 223 Rem. chambered varmint style rifle, and again no issues with magazines. PRI's are not cheap, but I will pay for reliability. I was all excited about ASC mags, because of reviews here, and the lower price. But when I started using them, at my range, testing loads, and started to have feeding issues, I quickly lost interest in them. I tried giving them to my Son, for his 6.8 SPC, and he ended up giving them back, and ordering some PRI mags. YMMV
For high capacity mags, Barrett 30 rounders are rock solid, too.
Squeeze