Personally, I don't care for 30 rounders in either an AR15 or Mini-30 in 7.62x39, but 20 rounders are perfect. The 7.62x39 30s are too long and catch on things. I know from personal experience the ASC 20 round 7.62x39 AR15 mags functed 100% with both Tulammo 8M3 124 HPs, and both Nosler 123 and Hornady 123 reloads.

In fact even on my 5,56 AR, I prefer 20s. Back when I used AR15s or Mini-14s as LEO patrol carbines, I almost always used 20s in the weapon.