At close range, the 20 bore or .62 smoothbore will 'throw' a decent pattern with solid ball and 3 buckshot. We (Taylor and I) did this in my rifled .54 flint pistol & his .58 smoothbore flint pistol. At 12 yards, the big ball was always centered with the 3 buckshot landing radially around the centre hit.
On a B-27 target, the single ball was always in the 10 ring, with the buckshot landing in the outer 9 ring to inner 8 ring. The spread was basically all in an 8 to 9" circle around the centre point.