Its better for your rifle to strip the black paint off that may or may not provide any corrosion resistance. It was put on by a retailer/importer/wholesaler as 'cover up' at some point in the dealing process for looks alone. Bluing with cold blue is very easy yet takes a few hours and patience. The results are worth it. Simply use acetone or mineral spirits and a brush, remove all paint. Dry the metal then apply liquid cold blue with a sponge. let sit on a towel for approx 10 minutes then dunk in plain water or spray with hose. Dry with your air compressor, Then use fine steel wool to scrub the part. Repeat the process several times until desired blue is achieved. Approx 3-6 coats should be more than enough.
of course complete takedown in required, all parts much be taken down to their base level. Most difficult parts are trigger assembly's but view Youtube and so long as you built Lego's as a child and have basic tools you should be able to accomplish this. I could and I am the kind of guy who purposely does not own a powered saw or chainsaw for the preservation of my fingers.