I know lots of people shy away from the Russian stuff, but my M&P 15 has had TONS of it through it. It's usually what I shoot when I do get to go out and shoot. I buy it when Academy has it on sale and can pick it up cheap.
I figure if I ever actually "NEED" my rifle, it's good to know it'll run as good on the cheap stuff as the more expensive brass cased ammo. You do give up some accuracy though with the Russian ammo, as well as it being much more dirty, and smells like piss when you shoot it lol.