Oh crap, I forgot he said this rifle was from the 80's! I don't think they used LocTite back then. They just used the biggest forearmed man on the planet to tighten the screws Or it always seemed that way to me! Not to mention I would like to find the man who invented the slotted screw (flathead) and beat him over the head repeatedly with my biggest screwdriver! BPS's suggestion of heat is probably going to be your best answer.