i'm not sure, I have a .223, and someone once told me to not ever shoot ball ammo through my rifle, in that it was not intended to shoot ball ammo, just the regular .223 rounds...but i'm not sure, I've just been playing it safe. I don't think i'd shoot much of the 5.56 ammo anyways, most of it is dirty powder with lubed bullets and cases made for semi's and I don't need that gunking up my chamber