The new (crappy) Express finishes are often too rough for the normal light coat of oil - the roughness means the surface area that needs to be covered has increased by a lot.
But the solution I've read (it may even have been from Dave McC) is simply to add a step to the first cleaning when you get the shotgun. After you break it down and clean it, take a good CLP or gun oil and
liberally oil the finish - I mean, get it wet and drippy. Let soak for at least a few hours, if not longer. After the soak, wipe the excess off and clean&oil normally in the future. You'll probably only need to do this once, and that should take care of the problem by making sure all the little nooks and crannies get a base layer of oil into them - but note that if you ever degrease it for whatever reason you'll need to repeat the process.
If it still has problems you can try using a good coat of paste wax. If you STILL have problems it might be time to look into a can of spray paint.
If you're really unlucky it may keep rusting no matter what you do - one guy I read had that happen. He tried everything: oil, grease, wax, etc. It just kept rusting. He finally totally stripped the thing and refinished it and had no problems thereafter. I don't know much about bluing, but maybe he had a bad blue job (the whatevers weren't neutralized)? Or, he said it was bought at a fire-sale - if he meant that literally odd chemicals from the smoke may have gotten into the finish.
Anyway, the above method should work for most rough-finished Expresses. If you are really concerned, of course, you can just do what I did and get a Marine Magnum - I'm sure it's
possible for that thing to rust, but I'm not sure how I'd go about doing it.
- Cliff