I don’t see why you wouldn’t be able to shoot a 55 gr well, not sure why you would go too much under that. The Sierra match king or a Berger or hornady eld are the hot bullets and other than that there isn’t too much to it. I’d go 69 mk for the first try myself if I was doing 300 paper. Others may beat it out but the mk should be accurate for just about anything. It’s a safe option.