Swifty did you try soaking your barrel in alcohol and/or using break cleaner? The carrier or solvent in the bottles is alcohol.
Any chemist out there who know of a solvent for this stuff? Poly methyl-silazane, it is a polymer with nano silica particles in it that are 0.25 microns supposedly.
Years ago I had a situation in which I suspected that I had incorrectly installed UBC (before the name change to DBC, it was called Ultra Bore Coat) in a rifle. I spoke with the owner of UBC and designer of the coating, and he told me that he knew of no way to remove the coating chemically, and that mechanical removal would be necessary. He sent me a kit with different grades of specialized, very fine sand paper, and suggested I might try that. I didn't like the idea of subjecting my bore to that type of treatment, and I wasn't sure that the coating was incorrectly applied, so I decided to just shoot and cure it and see what happened. It turned out to be fine, so I never did pursue the idea any further, but I thought that info might be useful in shedding a little light on your question.
To respond to your OP, while I haven't used it in shotgun barrels, I was told by the original owner of the company that DBC can be applied to chokes that are installed in the barrel without any issues. It is cured properly in shotgun barrels, and apparently reduces plastic fouling substantially. Sorry I can't report on first-hand experience.
