Oh there is so much more to shooting a traditional type muzzleloader than just point and shoot. Especially with a DB trigger setup such as on a Renegade. Hand position, stock position, form, breathing, follow through, and much more. I will agree that Bore Butter is very bad for barrels when people just use hot soapy water to clean. BB has ingredients in it that will cause buildup that doesn't come out with just soap and water. A good water based solvent needs to be used when using BB. I currently use my own little concoction for lube when using my Maxi's and PRB's and I also run around 20-30 strokes of JB bore paste every 200 or so rounds.
And yes sir, cleaning procedures can and will affect accuracy as easily as improperly putting it back together. Inconsistent pressures on the wedge key when putting the stock and barrel back together can throw the accuracy to hell. Blown out nipple, same thing.