the easiest way to remove rust from a gun?

You can use 0000 steel wool on gun blue. Use it with some RB-17. It won't hurt the blue. I have used it on shotguns costing several thousand dollars. What have you got to lose anyway? Good luck.

http://www.rb-treasures.com/product3.html

After many years in the military, I have cleaned many weapons that developed light external rust. The only thing we ever used was CLP, cotton rags, and an AP brush (like a tooth brush). If you can just feel the surface being slightly rough, but you can't see it, you did a great job and you should stop there. A working gun is a tool. Things happen to it. Over time they end up looking used. After rusting, there is no way short of refinishing it to make it absolutely 100%. My rule was that when a clean white rag can wipe off the oil and there isn't any discoloration but the oil, then you did the best you could.

Put break-free CLP on the metal, leave it for a few hours or even overnight.

Then rub lightly with OOOO steel wool

This method was suggested by the curator of a firearms museum. It does work, and does not damage your gun.

Start out with brass wool. It is available at real paint stores. Use it and oil. If that does not work, you can try steel wool. It will probably damage some of the bluing.

Never steel wool---Bronze wool--

I refinish the best guns ever made in the world--and have for 35 yrs, Steel wool is not in the building.

Lightly brush it with some fine scotch brite or fine steel wool. Be careful to not rub the blueing off though. If that doesnt finish the job than what you feel is tiny pits.

Yes, copper or bronze wool and/or brass brush. No steel of any type.

You can use very fine sandpaper like they do in automobile body shops, number 220 grit or 300. You will probably need to blue it again when finished.

steel wool