I'm considering a colt 6920. The price of the rifle is not what I'm worried about, its the ammo. I would want to stockpile 7000 to 10000 rounds if I was to get the rifle. Is steel cased bulk Russian ok for the colt 6920? What bulk ammo do you recommend for SHTF? Cabellas has thier house brand .223 55 grain 1000 rounds for $260, no shipping or tax. What do you shoot through your AR?