Two of my fellow RSOs have golf ball cannons, its a M44 Mosin Nagant with a iron tube welded to the bayonet lug. You cover a golf ball with a tissue/paper, push it into the tube, load up a blank 7.62x54R round, aim, and fire! And the golf ball goes flying. We did this in the backwoods and the golf ball must have gone over 700 yards before it was lost from sight.
But its’ still a firearm, gotta watch where you aim it.
Yesterday (Sunday) a golf ball was fired, it hit the 25 yard beam and came straight back. It then hit the front of rifle bench 12 then bounced back hitting another pole and coming to a rest in front of rifle bench 13.
A picture of the 25yr beam: