Add booze and it becomes a sport! Lol
To the above, and what I said, rough out 150ft and see what a BB from his rifle feels like on your back, then move in. Then make im be the target of his own rifle. If he's not responsible enough to understand after being shot by it at a certain distance he shouldn't shoot anyone inside of that distance, you just tell him to go shoot at pop cans while the rest of you play.