Q:I recently went on a duck hunt and two hours later I noticed my Remington 870 had about a dozen rust spots. I did everything I was supposed to; I wiped it down and changed gun cases. The spots have not pitted, but even rubbing the areas with Hoppe's No. 9 and oil with a patch will not remove them. How can I remove light rust without hurting the bluing? Also, do you have any suggestions for preventing rust formation while transporting firearms after a hunt?
A: Unfortunately, there is nothing you can do to remove the rust from bluing without damaging it. You can use some very, very fine steel wool and oil to remove the rust, but the bluing will probably be removed or thinned so that it doesn't match the remainder of the finish.
However, there is a multitude of products to assist in rust prevention. Essentially, top-shelf gun oils and CLP’s should suffice under normal wet conditions. So far we've had luck with Birchwood Casey Sheath (now called Barricade) or Outers Metal Seal, which penetrate moisture and deposit a wax on the surface of the metal that protects it.
If you hunt in salt or brackish water, be sure to flush your shotgun with plenty of fresh water as soon as you get to shore (nothing will remove salt water except plenty of fresh water). Then, you can dry it and apply a product such as Barricade or Metal Seal.
A wet or damp case during transport is a perfect storm for not only rust but mold as well. Stringent maintenance, quality oils and dry storage will help in your future endeavors.