Miss Um... i know this is old , but i own the same rifle and caliber, m77 international and had same issues with acuracy.. The 150 grain superformance rounds would even tumble, and hit target sideways. In these short, slow rifling barrels i shoot bargain brand core loks in 180 grain round nose soft points..just cant stabilize over 2700 fps.. Shoots one inch groups. Kindda stinks making your .308 shoot 30-30 speeds but kills deer real dead.. Also.. That manichner stock heats that barrel up quick after five or six shots... Hope this helps. I Quoted the wrong reply i guess....Sent from my LGLS620 using Lake Ontario United mobile app