I'll bet $10 it's lint, I've seen it before. Look at the bottom of the bottom picture. See how the lint lays over the top of the striations of the barrel ? Lint isn't going to "pit" a barrel. No offense intended, but I'm also willing to bet this may be the first time you've scoped your barrel. This is why so many people are against barrel scopes. Additionally, many barrels look like shit, but shoot lights out.
Something else that should make you feel better.....I've been there, done that, got the T-shirt. My barrel scope comes out of the tool box rarely anymore. I've spent a lot of time chasing Goblins because of it. It's not a bad tool, but one has to know how to interpret the information the tool is providing.
Blow out the barrel and post your results, particularly if I'm wrong. It always helps closing the loop, good or bad.