Thank you all for your confidence in me. For spot blueing,first I would try this from Brownells. Oxpho blue CREAM
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This is the cream version. Much easier to control. Follow the directions and repeat the process about 5 or 6 times. If that don't do it send me pics and I can eyeball what kind of blue we are looking at then I can advise you. Now if the whole gun needs to be done....I can make some recommendations for people in your area. Just for the record,stainless will not take bluing of any kind. You may PM me and we can exchange phone numbers if you would like to discuss your options.