The worst I've ever seen was a .30-30 lever gun. My brother in law brought his son in law's rifle to check zero. He had a box each of factory Remington and Winchester ammo of the same weight bullet. We shot the rifle at 100 yards. The rifle was plenty accurate enough, but the groups were 8 inches separated vertically. So we set it for one or the other and told the owner to only use that ammo.
