I'll offer up a couple suggestions. First I would use Federal Gold Medal in either 168 or 175 until you get the problem worked out. The surplus ammo, Remington 150, and winchester are not near the ammo that the Federal gmm is. The black hills should shoot well, but I'd stick with the Fed GMM to eliminate the possibility of the ammo being any part of the problem. Another thing to check is your parallax, I've seen it be the case many times even on the best scopes made. Look through your scope at your target and move your head around slightly, your crosshairs should not move on the target, if they do you've got parallax problems, begin adjusting until the crosshairs do not move. Another area to check very closely is the crown, if its nicked or scratched it'll never shoot. Lastly check the torque on the action screws, it should be around 65 inch pounds.
Hope this helps.