A family member brought over a Parker Brothers Trojan double barrel 20 gauge shot that she wanted me to clean. The outside is in used but good condition, however, both barrels have pitting in the bore just ahead of the chamber. I know it’s subjective, but I would call it moderate to mild pitting. It extends 3 or 4 inches down the bore. I know shotguns don’t generate high pressure, but would like some opinions of what I need to do about this. Is it safe to shoot field loads?

Yes.