Also, have a look at your crown to make sure it is perfect. ANY deviation in the crown "square" will cause crappy grouping. I'd call Ruger customer service and see if they have any suggestions after you have gone over your screws and crown. It could be a bad mating job (barrel to action mate), action just too far out of true, chamber too large causing inconsistent pressures, bunch of burs left over from rifling, poor stock fit causing the forearm to put pressure on the barrel. It could be any number of things. Ruger is pretty good about standing behind their products. Personally, I'd already be on the phone with them if I were you.