Originally Posted by robocop10mm
If it is loose enough (even with a patch) to be pushed down the barrel, the accuracy will suffer. A tight fit is essential for complete burn of the powder and an accurate shot. Traditionally the smooth bore is used unpatched. The fit is loose enough to ram with relative ease allowing for fouling build up in subsequent shots. The ball obturates when fired to fill the bore.
Of interest, windage was a given for cannon and ball fit in the British system. There seems to have been a consistency of 1/4in difference in sizes for the range of cannon 3.75lb Minion up to 36lb Demi Cannon. This was because it was never known if the casting didn't produce flaws in the barrel.
This factor must have produced unpredictable results in accuracy.