Re: ABS Barrel
Have you thought about having that barrel Cryo'd??? It's a VERY slow, gentle operation. I've done it on a few barrels that it did wonders to. I don't think I'd worry about the carbon as I've seen them put light bulbs through the cryogenic process and they came out without breaking (and lasted longer as a side benefit.
I wouldn't give up on that barrel. Check out Badger Cryogenics in Baraboo, WI. He's done my work for me very reasonably ($40 or so).