Tom.
I have the Renegade in.54 cal. which has a 26 in. 1/48 twist barrel. I use the T/C 430gr. Maxi Ball. That is the middle weight bullet T/C offered for the .54. With 100gr. of FF I usually put two touching and one just off for about a 1-1.5 inch group at 100 yards using peep sights. That's without swabbing the bore between shots.
Same results with mine. Somewhere around here, I’ve got a target with 3 round balls touching at 100 yards with that same load. But my eyes were much better way back then! 🤠
Mine loves round balls. But it wouldn’t shoot any plastic sabo bullet combo worth a damn. No matter what I tried
I will add that the only thing I’ve ever treated the bore with is T/C Bore Butter. And I only shoot real BP.
Also, The Lyman BP Book mentioned above is the one I highly recommend for beginners. Great source of info!