Greetings, fellow Mossberg addict! We now have a 12 step program- step 1 is box up all your Mossy .22s and send them to ME!
Just for future needs, Vic & Cheryl Havlin at havlinsales.com for anything Mossberg. Really nice folks, good source of parts and info, they also run the Mossberg Collectors Assoc- and Vic used to work for Mossberg.
Re: Rust. Weeeeeellll- Bluing IS controlled rusting, so anything that fully removes rust (like Naval Jelly) also removes bluing.
For light surface rust- remove action from wood. Wet generously with a good light oil (product called KROIL is best penetrant oil I know of) Let it soak in for a day. Use a clean cloth (burlap works) wet with oil. Rub. When cloth gets dirty, shift to a clean spot- rust on cloth is more abrasive than cloth. Keep damp with oil, rub until arm falls off. Repeat with other arm. It is amazing how much you can do with a very low tech approach.
Heavy rust- same soak with penetrant oil. Use a COPPER Chore Boy pot scrubber, dampened with oil. Be sure it is not copper plated steel. Rub gently. Follow up with coarse cloth oil routine. Will remove copper that has transferred to gun.
Pitting- nothing removes it- metal has gone bye bye. Use penetrant oil to stop rust, chore boy to remove loose rust.
There are other techniques, but they can damage bluing. Easy does it, take your time. elbow grease and patience.