I have a rifle from a friend he wants to sell. He has never shot the rifle. He has owned it for ten years. It is a Remington 700 1967 varmint barreled .243. It does not appear to be shot much. I want to buy the rifle or sell it for him. What twist rate is it? What factory ammo will group best? I know it is a barrel burning round. What should I do to check the barrel is not burnt out?