You can learn a LOT from your patch. What condition is the patch in after firing it? If your bore is pitted and rough and is the problem, it will tear the patch up. Check for that before taking a deep dive into fixing something blindly. Bores can "look" horrible, but shoot just fine, so look at a fired patch or three before getting too excited.
Patch material might have changed since it shot well decades ago. You may need to not take it for granted and try other patch materials, other patch thicknesses, other patch lubes, maybe even other ball diameters.
It's a 1:48 twist if it's an original T/C barrel. It's a compromise to shoot balls and conicals "ok". It will never really shoot either exceptionally. My early days with BP were all Renegades and Hawkens. Nothing ever really wowed me until I got into 1:66 or slower twists for roundballs, and 1:24 twists for inlines and saboted pistol bullets.
Sights: it ain't gonna shoot worth a [bleep] if you can't drive the sights.
I'll add too, that your loading method can make a big difference with roundballs. It really doesn't matter "how" you do it, as long as you do it exactly the same way each time. I like a medium compression on my charges. More than just touching, but not pounded tight. I push the patched ball down onto the charge, then apply just enough pressure to "seat" the ball to a mark I've put on the ramrod even with the muzzle. This ensures the ball is actually seated on the charge, and ensures each load has the same amount of compression each time. I never hammer the load home and bounce the ramrod like Hollywood does it. That can upset the roundness of a soft lead ball and affect its flight characteristics which in truth are poor even when it's perfect.
^^^^This about all you need to know in one handy post. My only addition, use real black powder, 3FFF chrono's with a lower velocity spread than 2FF....forget wannabe powders until you get your load developed, then if you insist, try the wannabes.
