John,
I've shot 45, 55, and 69 grain stuff through mine thus far. I only have 85 rounds on the rifle to this point. The 55 grain stuff was Remington metal case and it was about a 3" grouping. The 45 grain was hollow points and they were about a 2" grouping. Then I shot the 69 grain stuff in the above target.
I have some 52 and 62 grain ammo I want to try but have not been back out.