Here is a target at 25 yards. I had several targets at 50 yards, but at that point I was having issues with the patches I was using and none of those were representitive of the firearm. Just the shooter.
That is around 3" in both directions and considering there is no rear sight and the front sight is attached to the upper band and moves 3/16" I figure that is about as good as it is going to get.
As far as the patches are concerned, I do have some pitting in the barrel and the patches were sized for .60-.69 so just came to the equator of the round ball. It seems the pitting would sometimes 'grab' the patch and the round ball would fall to the bottom above the patch. Accuracy is pretty miserable when that happens.
I did try both the .648 and .662 round balls with two different sized patches of .010 and .018. The .018 works pretty well with the .648 round ball but is subject to the above issue. The .010 and .662 was still a little too tight for easy ramming. In order to use the .010 and the .648 round balls, I had to double up the .010 patches. This actually was easier to load as I could spread them apart and the issue of the ball falling below the patch was easier to deal with with the two patches. This combination was actuall pretty tight. I think I'm going to test with a square patch of .018 thickness that allows the patch to extend over the top of the round ball.