RE: range test with the kentucky 50 cal
Most kentuck rifles are built as strickly PRB guns with a slow twist and will shoot best at 50 yds and over with about half the ball weight in powder. It sounds like maybe your patch is to thin or your ball to small your patches should be whole and not burned[ now I did not say they should not be black with some powders just not burned].
Speaking personally I gave up trying to shoot 777 with PRB or with #11 caps a long time a go it just was not designed fpr that use and would not work as well for me as Pyrodex or black. Lee