I have used Maas Polish on chrome guns. I have also used to clean blued guns. It will work fine on hot blued guns which blue into the metal. I would not use it on cold blue areas. It works well on stainless also.
I recently used it on a 67 vintage .22 Colt Buntline that was very dull looking when I bought it. It also had a few tiny rust specs. It looked like new after using the Maas.
Here is a link describing its use on guns: GUN POLISH