Though I’ve heard mention of carbon ring build-up it wasn’t until I got to the 6 Creedmoor portion of the large/small rifle primer comparison (last Kauber’s Corner article) was I aware first hand of the problems caused by carbon (powder residue) build up in the bore.
An established carbon ring manifests itself with sudden and progressive spikes in pressure; pressures bordering on the dangerous and in most cases degradation inaccuracy will result. The tremendous amount of heat and pressure transforms carbon fouling into a ceramic coating that is difficult to remove once it has welded itself in your rifling.
Every experienced match shooter, barrel builder, or gunsmith has his or her way of cleaning rifles but most will agree that a hard carbon ring can’t be removed by standard cleaning methods, it has to be scrubbed out. There lies the fine line between effectively removing the carbon ring and damaging your bore by using a compound too aggressive, overdoing the process, or a combination of both.
Not one to attempt to reinvent the wheel or waste time on the Internet trying to decipher the repeated BS from good, sage advice and recommendations, I’ll go directly to those I feel are true authorities based on years of personal experience and an application of said advice in the conduct of their livelihood. When I couldn’t figure out the pressure problems in my Benchmark Barrel built 6 Creedmoor I immediately drove the 20 minutes from home down to Arlington, WA to speak with my long time friends Ron Sinnema and Bill Broderick owner and manager respectively of Benchmark Barrels.
Carbon ring in the rifle bore can affect accuracy, pressure and velocity. It is more likely to occur in cartridges with large case capacity and small bore diameter. Carbon ring is best identified with a bore scope and will appear as dark and cracked areas of the bore. It is usually 1”-2” in front of the throat and chamber or within the first 30% of the bore.
