Rust is the archenemy of a firearm, and this is especially true for muzzleloading weapons. The black powder or powder substitute used to fire the ball from a muzzleloader is of high potassium salt content, which in turn sucks moisture from the air and absorbs water. This will cause rust and pitting inside the barrel if powder fouling is left unattended. The rust can eat away at the steel and cause poor accuracy. Cleaning your rusty barrel can be done, though this may involve a bit of sweat to scrub the rust away.
Items you will need
Gun cleaning solution/rust remover
Stainless steel sponge -- bore tip
Bore plunger
Bore cleaning patches
Bore polisher tip
Large tub
Step 1
Visually inspect your muzzleloader to ensure its completely unloaded.
Step 2
Remove your barrel from the stock if possible. Pour gun cleaning/rust remover solution into a tub. Soak it in the solution for one week. If you can't remove the barrel, ensure the breach is closed and pour the solution into the barrel and fill it up. Leave the weapon standing upright for one week.
Step 3
Inspect the barrel after removing it from the solution. Look for any large rust pits and target areas to scrub.
Step 4
Attach a stainless steel sponge bore tip to your bore plunger. Wet the sponge with gun cleaning solution.
Step 5
Remove or open the breech. Insert the plunger into the bore and scrub vigorously. Inspect the bore every 20 stokes to check for rust removal. Attach a new sponge tip if needed or if the tip begins to wear while cleaning. Continue scrubbing vigorously until the rust is no longer visible.
Step 6
Attach a cleaning patch tip to your bore plunger. Insert the plunger into the barrel and remove any metal shavings that might have came off of the steel sponge. Reapply cleaning patches as they become worn or dirty. Wipe all oily cleaning residue free from the bore once the rust is removed.
Step 7
Attach a bore polishing tip to the plunger. Buff the inside of the bore until no residue is present and a shine is seen.