Rust in bore.

[PartsMan]

What would you recommend to remove light rust in an old muzzle loader?
Doesn't appear to be pitted yet.

[Saloon slug]

WD40 and a bronze brush. The WD40 will get under the rust as you scrub patch it till clean then lube like you normally do. That should do the trick.

[kevthebassman]

You might also try running some extra fine steel wool down the bore on your cleaning jag.  Make sure that it is well saturated in your lubricant of choice.

 I bought a TC Renegade and the bore looked like the surface of the moon and was covered in rust and old black powder residue.  I gave it the steel wool treatment along with a good soak in Kroil and now it shoots good enough to kill a deer at 125 yards.  The bore is free of rust but still looks like hell.  As long as it shoots I don't mind.