What's a good BP cleaner and plastic solvent? Ballistol has been suggested. Shooter's Choice says it removes shotgun wad fouling-it works pretty good on choke tubes with a bronze brush. I was always told to shy away from petroleum solvents with BP-have always used hot water and Dawn dish soap, rinsed with almost boiling. While still warm a patch with wonderlube 1000+.
If you are going to use plastic sabots I would use the Shooters choice and a bronze brush to remove that plastic. Water and dish soap is good to remove the powder fowling and it does not need to be boiling. Hot from the tap is hot enough. I have had rifles that quit shooting groups until I removed all of the wonderlube from the bore. They went back to shooting accurately again. I will not put that stuff anywhere near a muzzleloader.
Petroleum based oils and lubes will mix with powder fowling and leave a tar like mess in your breach. I do use them for rust protection after I have cleaned out all fowling and I wipe it out then pop a few caps to clear it from the nipple before the first loading. Never had an issue with it that way.
Scrub out all that wonderlube and I bet your rifle will start grouping again.
