You can also use a solvent or oil and a piece of stainless steel wool size 0000. It will take it off and polish the cylinder back to almost new appearance. It can also be used for taking light rust off a blued gun, with very, very little damage to the bluing. Be sure to use oil if doing a blued gun. Another product that I have used is the Stainless Steel cleaner my wife uses to clean her stainless cooking pots. If I use this, I usually disassemble the gun, rinse good in hot water after cleaning, blow dry with compresses air, then apply a good coat of oil.
Keep in mind, STAINLESS STEEL WILL RUST! It may appear as a light browning, or as pin size brown flecks. Most often it takes a long while for it to happen, this is the reason it is important to apply oil to the stainless gun.