As far as legality, with shot you can use a .50 on small game in PA but if using a single projectile, ball or bullet, a .40 or less is required in small game. As far as using shot in a rifled barrel, you will find Bronko is correct. Even using a shot cup will produce horrible patterning. Actually, using a shot cup will make it worse than using over and under cards. Even my 1:60 twist barrel produces horrible shot patterns after 20 feet. They just spray open incredibly fast because of the spin.