FWIW, it seems like they keep getting closer to working out the last few bugs. Broken bolts are still a problem although sticking to brass cases seems to help. Then again, who sticks to brass cases in that caliber? Deeper bolt heads with beefier lugs (somehow) and extraction with both a sense of mission and a lot of contact surface with the rim seem to be the last great frontiers left in the course of civilizing, or at least AR-izing, the 7.62x39 at this point.