DarylS is going to have to answer this one. For the life of me, I cannot get acceptable accuracy with round balls from a smooth-bore. Even tried shooting steel automotive CV-joint ball-bearings to avoid any deformation, still couldn't hold better than about 3 inches at 25 yds (from memory).

For me, it's base-wad slugs (read 'Brenneke') from the shottie, or a Paradox!