Not cheap, but worth it - Flitz 150 Gram Boxed Tube Metal, Plastic, Fiberglass Cleaner

Not cheap, but a little goes a long way. This and Simichrome (tough to find) are the 2 best metal polishes on the market. There are a few products that will remove burn rings from revolver cylinders, but only Flitz and Simichrome will do it without removing the bluing (check yours first). Mothers and the Blue Wonder stuff are way too aggressive and don't work so well as this. Flitz will slick up your revolver chambers real well - easy ejection. You can even use this to polish the headlight lenses on your car. Highly recommended, and these larger tubes work out cheaper. Do not use on nickel or electroplated surfaces.