First off, I got a chance to shoot the Mini30 recently... garbage half the time... which to me, means garbage all the time. A mag would shoot fine once, and then have problems with the next load. Nothing changed. It was just random, unsolvable problems.
There are two tricks to an AR in 7.62x39:
1. Cason Eng Enhanced Bolt and Firing Pin
2. C-Products DEFENSE "J-Mag" Magazines
Cason makes a new bolt that has all the bells and whistles going for it. They have several thousand round, full auto, on the same bolt. Steel or brass, it is devouring everything.
C-Products is now C-Products Defense, and their new designed 7.62x39 mag is called the J-Mag. They make a 28rd that fits in standard mag pouches. They also make a 35rd, but it's not released yet. The 35rd mag is the old 30rd banana style, but with the newer follower (out of the 28rd). The steel mags have double welds on the spine and come nitride treated. They really stood out at SHOT Show.
ASC mags are the most common out there, but have to be slightly modified (only if you bought 30's. The 10's run fine). Get out your dremmel and grind about 1/4" moon shape out of the front lip of the mag. That'll help the heavy cartridge clear the mag. Having M4 ramps on your receiver/barrel helps too. Makes sure those ramps are clear and flush.