i had that problem with my brand new SPS varmint. its not blued, but a matte finish. never in the rain, never wet...i couldnt figure it out. only gun out of a pile in my room that would rust. i put a dehumidifier in my room and no more rust on it. not totally sure why only IT would rust when theres countless guns in my room...but it did....now it dont. i kept it whiped down and clean too...