I've used EXTRA HOT soapy water, followed by dry patches and then T/C Bore Butter on a patch and then on the exposed metal for decades now; with ZERO corrosion.
The main commandment with a muzzleloader is to stay away from any modern gun lubricants with petroleum distillates. Black powder or black powder substitutes react with petroleum distillates and cause corrosion; use Bore Butter or similar products. Also, BP firearms need to be cleaned ASAP after shooting or once again, you will be fighting corrosion.
Tom
:yeah:x2, I also stick my smaller non plastic pieces in the oven on warm, it dries them out completely. No corrosion and I've had the gun for at least 10 years.
