Just got a SIG 556008, that butt stock is the poop!! I've shot 30 06 700bdl and M1A1 for years, there is one heck of alot of difference in a 30cal and a 223, I have only shot a XM carbine in the 223 cal. I have used the ammo I have for my carbines, 45gr Remington H.P. and 55gr Remington spire...