Gun Discoloration

[tooldummy]

A guy at work bought a stainless steel Smith and Wesson revolver the other day and has shot it very little. But, for no more than he has shot it, there seems to be a lot of discoloration around the cylinder and at the end of the barrel. He has tried cleaning it, but it isn’t cleaning easy. I suggested buffing it, and he tried that with a little Dremel grinder and a buffing wheel for it, but that hasn’t worked for him either. Is this normal, or do any of you have a suggestion for him to try?