Everything old is new again.In all honesty the only way I see to improve a smoothbore is to add a tail to the ball be it a dowel or line and drag.....
Scloppeteria, Capt. Henry Beaufroy, 1808:
"Another method also, which we have seen tried successfully enough at 100 yards, but no further, was to bore in a common musket ball a small hole about two tenths of an inch diameter : a piece of string from four inches to fourteen, doubled in the middle being inserted into the hole, and the lead beat over it, the two ends were left hanging loosely from the lead : on firing balls prepared in this way against the common spherical ball, the former had a decided advantage, as to the up and down direction, the deviation to the right and left being comparatively trifling, while the latter were in all manner of directions round the target."
Spence