I had this same debacle last year, as I had a perfectly good muzzleloader passed down to me. What I quickly learned was the bore of that rifle was oversized and not consistent diameter for pushing full bore conicals down. Since I couldn’t use sabots, I determined my money saving efforts were bust and had to come up with a new rifle stat.
I ended up with a Knight mountaineer that I found used, because lead times on new Knights were nuts last year. That rifle was absolutely outstanding down range and I used it to put down my 6pt bull, but it was also a boat anchor during my backpack hunt.
I ended up ordering a Knight UL this spring and figure this is the rifle I’ll use for any tag I can legally hunt with it on for the rest of my life. Great muzzleloader, just checks all of the boxes for me.