If the rust is a bit more than just a light surface dusting, put some oil on it and scrape it with the edge of a copper penny. It will remove the rust with no damage to the blue. Also leaves a coppery smear, but it will wipe right off.
A mild warning -- even very fine steel wool can start to remove bluing if you get too enthusiastic, so go easy and take it a bit at a time.
A mild warning -- even very fine steel wool can start to remove bluing if you get too enthusiastic, so go easy and take it a bit at a time.
