I had an '06 that was as bad as or worse than what you describe. Even half a dozen foaming bore cleaner sessions wouldn't fix it. I fire lapped with the Beartooth Bullets kit, and that helped significantly, but it still fell into the 'copper mine' category.

I did fix it in the end, though. Know how? Ultimate Bore Coat. Search for it, or read up over on 24hourcampfire.com.

One app took care of it (remember that I had fire lapped first, though. I think their site is ultimatecoatingsinc.com, but I may not be remembering that correctly.