A surplus Star BM arrived last week. It has surface rust on the outside of the slide and frame, the extractor and the trigger. The internals have no sign of rust though in need of carbon-cleaning. I Thoroughly cleaned it with rubbing alcohol and then used FP-10 to complete the job. There remains the issue of rust. Does a copper brush help? What about WD40? Please let me know your thoughts and suggestions.

000 steel wool with oil.

Bob

Use a pre 1982 penny with some oil. Won't harm the bluing under the rust.

0000 steel wool, dry and rotate often. If you use oil, it builds up a slurry and becomes like a paste which mars the good finish.

I've done this a few times on old shotguns to good effect, though it leaves a mottled finish because of the damage the rust did.

On a Norinco Hunter, the speckling was pretty bad so I had to take more extreme measures and bring out the Dremel with buffing finish removal tool. Took it down to bare metal and did three coats of Brownell's Oxpho creme blue.

Most CLP gun oils will remove surface rust. Try Slip 2000 or similar synthetic with a microfiber cloth before resorting to an abrasive. For tight corners use a VERY LOW speed battery powered Dremel cotton drum with oil.