I've been using Bore Tech Eliminator for the last 2 years. It works pretty well on barrels that get maintained regularly. I'm not sure about the barrel you've described? I live a few doors away from a guy who shoots long-range competition, he turned me on to some of his tricks. He wraps a cleaning patch around a nylon brush then saturates it with Bore Tech to "wet" the bore doing a few passes from the breach. Then waits a few minutes to run a nylon brush thru the bore 5 or 6 passes, then has a go with the patches on a cheap plastic jig on a Tipton carbon fiber rod until they start coming reasonably clean. It's also important to wipe down the cleaning rod each time you change to a different "stage". In your situation, I would try his break-in technique, which I have used a few times with a new barrel. As mentioned in other posts, Kroil and J-B's bore paste. Put several Tipton felt cleaning pellets on a bronze cleaning jag, since the plastic ones don't lend themselves well to all the pushing and pulling, saturated with Kroil and run them thru the bore 5-6 passes or so, from the breach. Then put a few new cleaning pellets on the metal jag and load up with the J-B's bore paste and a few more drops of Kroil then do about 15 passes, pushing and pulling. Run a nylon brush and a few clean patches to get what's left of the paste out of the bore, then finally a lightly oiled patch. Don't forget to clean the chamber! I use a 30 cal brush, for example my 22-250, with patches wrapped around it. I know it sounds like a lot of work, but hopefully, it will save the barrel? Hope this helps? There are a lot of ways you can approach your problem, pick a few and have at it!!