Hey Guys,
  I need some advice for a buddy of mine. A Few years ago, he got one of those Muzzleloader kits for Christmas. He wasn't really into it, so he stuck it away in the garage for a while. To make a long story short, The bbl was in a padded gun case, and it got wet. He never knew about it, untill he took the bbl out. Its rusted pretty good. I am thinking the bbl is stainless, I am not sure, though. He's tried to get some of it off with some 1500 grit sandpaper. Anything other suggestions I could give him? I realize it won't have its full shine back, but would like to get it looking good.   Thanks much!

-Jared

The Electrolytic Rust Removal FAQ

[url]http://www.bhi.co.uk/hints/rust.htm[/url]

also worth a read,

[url]http://www.metalwebnews.com/howto/rust/rust.html[/url]

If the barrel is silver colored or stainless, the rust/corrosion is green colored. I always used a product called flitz. It was a paste mild abrasive that combined with elbow grease removed corrosion. If it's a blued finish, soaking the rust in hoppe's #9 for a few hours to overnight will help, then rubbing with 0000 (four ought) steel wool will help get the surface rust off. 0000 is soft and does not hurt the finish but helps remove the rust. If it's pitted into the metal, you may need to have it reblued. When they take the finish off, they help take away the pits.

This is NOT always the case, as it will actually depend upon the carbon content of the steel being used in the stainless manufacturing process...

That very well could be. I'm not a manufacturer, but in the shop I worked in I never saw stainless barrels that had corrosion spots other than green colored specks. These were predominantly firearms made by the major manufacturers and were usually hunting rifles or stainless pistols or knives. What other descriptions are there?

If its not pitted, get some pencil erasers and work at it.  Works good on knives.