Scraping carbon out of the star chamber is nearly impossible. Star scraper brushes loosen the carbon, but don't remove it. The solution is to use the wool star shaped chamber pads after using the brush. This will remove the already loosened carbon.

20 Wool Chamber Pads per Package
Removes Loosened Carbon from Star Chamber
Evenly Distributes Solvents and Lubricants
Precision Cut to Fit AR-15 Star Chambers