Gun maintenance is essential for the firearm to operate at its optimal performance level. Rust and rust pits, if not removed, can build up and ruin the accuracy of the weapon or create hazards when firing. Properly cleaning your gun barrel–inside and out–periodically will help you avoid such problems. A rusty finish is also unsightly, and makes the weapon appear poorly maintained, and can ruin the overall value should you wish to trade or sell the weapon. Removing rust form the barrel of your firearm isn't difficult if you have an appropriate gun-cleaning kit.
Unload your weapon completely. Remove the magazine if applicable, then visually inspect the chamber to ensure that no live ammo is present in the weapon.
Look down the bore to check for corrosion and rust pits. If the barrel has a lot of rust, remove the barrel completely, then spray the barrel–inside and out–with CLP. Place the barrel in a plastic bag to let the barrel soak. Let it soak for about a week to help loosen the rust.
Coat the metal brush tip of a bore plunger with a few drops of CLP, then plunge the barrel, from receiver end to muzzle, in and out for as long as it takes to remove any rust.
Replace the metal brush tip with a cloth-buffing tip on the bore plunger. Coat the tip with CLP, then plunge the bore again in the same manner as with the metal tip. This will remove any rust or debris loosened by the metal tip. Rinse the tip off and dry thoroughly, then reapply the CLP and plunge the bore until no residue remains on the brush tip.
Coat the outside of the barrel with CLP, and use a soft-texture steel wool pad to remove rusted areas along the length of the barrel. Note that you must use extremely light pressure when using steel wool to avoid scratching the finish. If you don't feel comfortable using steel wool, use a nylon bristle gun-cleaning brush. The brush can be used with hard pressure, though it will take longer to remove rust.
Never attempt maintenance on a loaded firearm.