I just bought a 870 Super Magnum Express. I got a great deal on the gun, but the guy I got it from keep it in his shop and it has a light coat of surface rust on it. What is the best way to memove this? I tried Flintz, but I didn't have a lot of success. The surface is rough not smooth. Any ideas before I take it to the gunsmith and let him have a go at it?

Flitz will remove blue if you're not careful. I'd coat the metal in a good penetrating oil then try scrubbing it with bronze wool. The bronze wool is softer than your blueing and shouldn't hurt anything. If the metal has deep rust or pitting, you won't have any choice but to remove some of the blueing to remove the rust.

If all else fails, sandpaper definatly takes rust off but the blueing wont stay either, I had todo this with a old Marlin .22

Depending on the kind of rustit is. If it is very light rust,I like to use (blue wonder's) gun cleaner. It removes rust without removing the bluing (itwon't evenremove new bluing)

what you have to do is get the finest steel wool that you can find like 000. then you get out your (blue wonder gun cleaner) generously apply it over the area where you see the rust. Then take your fine steel wool and rub lightly over the rust (working in your blue wonder gun cleaner)

Then, get out a blow dryer and heat the area up that has the gun cleaner on it (this will open the pores in the steel and causethe gun cleaner toreact)....after this take a very clean cloth and wipe off all the gun cleaner. (Your rag should have a rusty brown color on it.) Then apply one more coat of gun cleaner on the area and heat again. You dont have to use the steel wool again, unless the rust is bad. After wiping the second application of gun cleaner off, oil your gun like you normally would when you put it away.

Some guys also take a good oil and rub steel wool over it. This also works if the rust is not severe.

If the rust is severe...you can try to cold blue it yourself (which is not the easiest to make blend with the surrounding blue) because cold blue tends to be blotchy.
or you can take it to be reblued professionally...(this would suck)[:'(]...

good luck ...I really hope you can remove the rust without much hassle...I would hate to see you have to go to other means.

I have used 0000 stealwool and a good grade of penterating oil on light rust. Use the steel wool lightly though! The brass wool would be better but never got my hands on any> Zeak

You can buy bronze wool from Brownells or most boat supply places.
Avoid steel wool if you can It will cut into the blueing, unlike the bronze wool.