Just want to point out that there is a huge difference between normal carbon in the barrel and the hard carbon ring at the end of the chamber neck. Different things entirely.
The person that comes up with a chemical to easily remove the hard carbon ring will have invented a better mousetrap and all precision shooters will beat a path to his door.
Couldn't agree more. I had pretty good luck with Bore Tech, several days, and a nylon brush. Carbon ring gone, but it was a lot of work.