If you have a brass bore brushsome solvent, along with some J-B Bore Paste you can fix that and get the barrel back to shine like new. First thing you need to do is remove the barrel from the stock and take the striker, trigger assemblyand breech plug off, so you can look through the pipe/barrel. Pay special attention to the threads where the breech plug screws into. This is not an area of any rifle you ever want rust to start forming. You rust them threads, and you could damage the integrity of the ability of the breech plug to with stand pressures when firing. Using the brass brush dip that in solvent and then Look through that barrel towards a light. Do you see any rust?

Now put your brass bore brush on a strong range rod if you have one, or put an extension T on your rifle's (the need for range and cleaning rods is essential in taking care of muzzleloaders as far as I am concerned) so you can push all the way through that rifle. With the solvent on the brass brush do about fifteen long strokes letting the brass brush spin with the rifling if it wants to. This will help clean out the rifling and it protects the life of your brass brush. The brass brush will also clean between the threads of the breech area as well. Normally the breech threads do not rust because they are coated most of the time with a anti seize which also help to reduce the amount of oxygen able to reach the metal. No oxygen to metal, no rust normally.

After that put a cleaning jag on the ramrod and push a couple solvent patches through the rifle. Sometimes this alone will fix the rusting problem or at least stop it where it started. If the barrel still looks bad, then push two dry patches through the barrel and finally one patch with gun oil on it.

Now that the barrel is oiled, your next patch, smear some J-B Bore paste on it. Make sure the patch fits reasonably tight. A stroke is down and back. Do fifteen strokes with the J-B Bore Paste. Now change from that filthy black patch to another one. This time put less then before Bore paste on it, and give it another fifteen strokes. The way I like to run the ramrod is I sit in a chair and lock the T on the ramrod, under my feet. So the ramrod basically stick up in the air like a pole. Then I take the barrel and force that over the ramrod because as the patch nears where the threads of the breech plug are, I can see or feel that with my finger. I stop before that area and then reverse directions with the patch. I do not ever scrub the breech plug threads with any bore paste. Normally the 30 strokes is enough to clean that barrel back to shine. If your barrel is really bad, there are more drastic measures.

After that I like to take and fill a large bucket with hotwater and some dish soap. You need to give the barrel a bath because alot of bore paste is water soluble and the best and fastest way to get it all out of your barrel is with a hot water bath. So dip your patch in the water, make sure the breech of the rifle is under the water level, and start to pump that patch up and down the barrel. This creates a syphon of course and forces the water to scrub the barrel as you work the patch. Anyonewho stole gas from the old man's car understands this principle. After about three or fourpatches, workingsoapy water up through the barrel, the majority of the bore paste should be gone.

Now run a couple more solvent patches through the barrel again. And finally some dry patches to make sure everything is removed and that the barrel is good and dry. It is very important that after all of this, you apply a quality gun oil to the inside of that rifle bore. The brush and bore paste has taken that barrel somewhat back to metal and removed anything that could protect it from rust. The oil should be put on thick. Let the barrel stand with the muzzle on a piece of cotton cloth or paper towel for an hour or so. This allows excess oil to naturally flow out the barrel on its own. Then run a dry patch through the barrel. If you look through the barrel now it should shine. The pitting is still there, but you have stopped the rust if there was any in the first place.

You can now wipe the barrel down with that cotton cloth it was sitting on and put the gun back together. If you are protecting the rifle with bore butter, you may want to rethink how you are applying that bore butter or change over to a gun oil. I used to get them rust patches also when I used bore butter.