You have several alternatives, a barrel cover(i.e. SnakeSkin), paint, or just let it be. If already a flat black camo isn't really madatory but if you don't wish to paint the covers will work(unless the barrel is of the type that moves such as the Browning A-5). If you want to paint(I paint mine!) the barrel will allow use of almost any paint. I reccomend an enamel in spray cans. For the wood I use paints designed for camoflaging bows and other archery equipment. It removes easily and won't harm the finish. The metal can be painted with any enamel paint. Remember the idea is to break up the lines of the barrel and have fun.. I start with a base coat and apply the other colors 1 after the other as drying permits. Use masking tape to create the camo effect. it comes out looking somewhat like the older 'tigerstripe' camo pattern...
Clean the barrel with acetone before painting (acetone leaves no residue). Cover sights and protect bore. Hang and paint away. It won't make your barrel rust proof any more than automobiles are rustproofed by their paint, it will help though. As to whether it will stand gunoil, I simply can't say. Depends on the oil and the paint used. I usually wipe mine down with oil, usually ATF, when putting them away and the painted ones have not had any problems yet. And the paint on this last one is of the BowPaint variety, which is very easy to remove. Comes off just fine with mineral spirits..
