It won’t take the rust off, but if you are able to get it clean or decide to buy another gun, definitely spray it with Jig-A-Loo before hunting in the rain, it will help to waterproof the gun barrel and prevent subsequent rust/corrosion. However, be sure to avoid spraying the product on the stock, forend and end butt as it makes the gun slippery to handle and shoulder.It is sold in most Wal-Mart/Home Depots and they also have it at www.jigaloo.com