Yeah, lapping the barrel would be like trying to polish away the grand canyon, I'm afraid. It might make it slightly easier to clean, though. I'm afraid I might just have to leave it as-is for a while, with bills for house repair coming in there aren't many free-floating pennies with my name on them as usual!
"... I cannot but conclude the bulk of your [politicians] to be the most pernicious race of little odious vermin that nature ever suffered to crawl upon the surface of the earth." ~ Jonathon Swift