Just out of curiosity, those of you who own 5.56mm AR15s, what is your preferred to ammo and why? As I see it there are a few options: the cheapest, the most accurate, or the most effective. I think M193 (55 grn) would be cheapest. Is M855 more accurate, in the right barrel twist? Do any of you forgo the military ammo for something like a 223 hunting bullet?