My worst rifle for corrosion would definitely be my mosin. Corrosive ammo and all.
On that old nazi killer, she gets water first. About 5 soaked patches. There's water all up in there.
Then I use "bore cleaner, rifle", dry patch or 2, then oil for the bore.
Not a speck of rust. Haven't used anything to remove the solvent.
It would have to be some really harsh stuff to keep go after steel after dry patches and fresh oil.
I do usually run about 5 passes of the brush, then a patch with a touch of solvent on it. Do this 3 times. Dry patches until no more solvent comes out on them. Then switch to oil, usually the oil will bring out some different junk, so I end up running about 3 oil patches, a dry, then an oil to finish it. After that, I don't really care what color comes out, because I know it's clean enough.
Wipe all steel parts down with an oily rag, and only touch the wood/sling when putting her away.
Zero rust.
ETA: on my modern guns, I use acetone in aerosol form (non-chlorinated brake cleaner), and blast all the junk out after using solvent. See joglee's thread about using grease. All the junk in my AR15s wipes right out with a rag. If I happened to use oil, then I will use brake cleaner to get it all out. I don't know if it will hurt my plastic, haven't gotten it on there.