So, I feel like an idiot. I left my 870 in it's soft case on my enclosed (and locked) back porch last night. I woke up this morning in a panic when I realized that I hadn't brought it in. My concern was that it could have been stolen. It wasn't, but when I opened the bag to check it out the entire thing is covered in a fine rust. One night! I'm assuming it must have been due to a cool night and a warm humid morning causing condensation. I still had no idea rust could move this fast. The rust is confined to the exterior barrel and the receiver, and is not present inside the barrel. What's the best way to clean this, and what maintenance should I be taking to prevent a recurrence? I've been under the foolish impression that a shotgun requires little maintenance, so I don't ever oil it, just clean it with a bore snake after shooting. Thanks!