Look up Mark Novak on youtube and then search his channel for "conserving" and "rust blue". Watch the videos and you will find a solution for your issue is to convert all that red rust by stripping all the small parts out of the gun and boiling every thing. Yeah your solution is a pot of boiling water. BTW, you do NOT have to remove the barrel from the frame, that is so well sealed any red rust in that joint will be converted to red rust by just the heat. Note, the boiling in combination with a lack of oxygen due to being submerged creates the chemical reaction that converts red rust into Black Oxide. What is really sweet about this process is that it will act to clean and restore the existing bluing. The end result after carding the finish is a much improved appearance and the only Chemical used is H2O.