I am not an expert but here is my take on why it would not work. With a golf ball, when the club strikes the ball it creates back spin. The dimples enhance the effect of the spin and cause the ball to rise. The more the ball spins the higher it rises. At the same time, any side spin will cause the ball to hook or slice. With a rifled barrel. side spin would always be created and the ball would curve (or at least spiral) rather than going straigt. With a smooth bore you would probably get back spin which would cause it to rise and go further but it may not be the best for aiming (trying to get a flat trejectory). I also bet that over the last several hundred years someone has tried it and the fact that you don't see them today is probably evidence that it is not the best set up.