I personally would not suggest anyone shoot shot out of a rifled bore. The reason is you will probably get no consistency in accuracy or patterns, it is possible to damage the bore of the current rifle, and the amount of shot you will be shooting would work for very small game only. The smallest smoothbore I think is a .56 caliber that was offered through T/C arms. I was always curious how well the smoothbore shot.

I personally shoot a .62 caliber smoothbore.