Owen, seems no one is addressing you original question. No, there is nothing you could have done to create pitting in a short time. You just uncovered it. Generally, light to moderate pitting has no influence on the safety of the gun, assuming proper ammunition is being used.
I shoot a number of damascus guns and don't vary their cleaning from fluid steel barreled ones. I will say a favorite cleaning tool of mine has become a bronze bristle brush wrapped with part of a Big 45 Frontier Metal Cleaner pad and spun with a drill back and forth through the bore. Does an incredible job of quickly removing lead or plastic.
