So ... I'm going to ask a stupid question. Are you "sure" they're "potholes"? I had a similar view of a new barrel and initially thought they were potholes. Then I started scrubbing the ever-lovin' crap out of it and they started to clean away. So admittedly, mine were a bit larger, with fewer occurrences, and most in the last 1/3 of the barrel, but my point is still (sort of) valid. Here's my advice ... if you're absolutely certain they're "ditches", then the barrel needs to be replaced by the maker. If you're not sure, zero in on a particular formation at a particular distance, and clean the barrel really well, and see if some of the "potholes" shrink or go away altogether. If you're sure they're actually holes, then please ignore me.