I stopped when I got performance bonus and crowd control. The more I thought about it, the more performance bonus made sense, as it grants reserve ammo on a kill. I seem to run out of HC ammo more often than other weapons. The selectables are armor piercing, field scout, and flared magwell. I had thought I'd run field scout, but I think flared magwell will make more sense. One takes it to 10 or 12 rounds (which is nice,) but the other basically doubles the reload speed, which seems more efficient.