I have a knight and so do alot of friends of mine. Here's what works for me and at least 3 of my friends...
100 grains of Pyrodex(either RS or Select)....with 260 grain knight sabots (I'm using jacketed)
My gun will shoot a 1 hole group at 50 yds and a 1.5" group at 100 yds.(from a bench rest) Just a suggestion... maybe it will work for you.

I've never tried anything else...so I can't really comment on what you are currently shooting. I just spit on a patch and swab the fouling out of the bore every couple shots when shooting from the bench. One thing I have found....I remove the breech plug and clean the gun every 20 or 25 shots at the most....any more than that...I've had alot of trouble getting it out...it gets real tight. Good luck.