I disagree with most of the posters so far. These rough phosphate finishes are well known to rust like this and it's super easy to see who didn't know how to take care of it when their gun rusted. Do not remove the rust or attempt to clean it. It will look like hammered dog poo if you aren't super careful. Oil will only hide the rust somewhat, not stop it. To convert that rust into something that will protect the finish and stop the rusting dead you need to boil it, in water. Distilled water is the best, get a good black finish. This IS how rust blue is done. It will look good when you are done. After that oil it heavily and wipe the excess off, it won't flash rust nearly as bad if you do. You can wax at this point also and it will do a good job of slowing down how fast it rusts. If you want it to stop rusting completely paint it. Satin black looks great on these, and the paint will seal the surface so that water can't get into the finish and rust it. Krylon works great, easy to touch up and it's cheap. It's been about as durable as the non-baked gun specific coatings for me as well.