I just recently bought one and so far I tried the Hornady SST 250 gr sabots, with 2 triple seven 50 gr pellets and triple seven primers. Had a pretty good group the first time I tried them, but then I went to the range a second time and had terrible scatter. Maybe plastic fouling don't know.
I use 2f bp, 45 cal 200 gr miniball bullet with crush rib sabot, shoots vg, I have had to experiment with every black powder gun I owned, just keep trying and you will hit the sweet one,
Good Luck, Stan