I've tried many different brands of ammo, Federal Gold Metal Ultra Match, CCI green tag, CCI pistol match, Fiocchi M320 match ,Aguilla SE extra in both standard and high volicity, the Remington golden bullet, Winchester super x , PMC scoremaster and PMC zapper and some others I will not bother to list. I have a Savage 223 varmint, a 270 and a tactical 308, and they all group very small. This is why I wanted to try one in 22 rim fire. By the way it is a heavy barrel, (bull barrel)! Thanks for the replies and info.