Carbon Bore fouling can be caused by a number of things , mainly by inconsistent or spiked Pressure .It will degrade accuracy as the heat as well as pressure transforms the fouling into a near ceramic type coating . Difficult to remove ,yet can be done chemically ,as well as by polishing . Bore Tech carbon remover and or Simichrome polish are effective .
It also has to do with temperature-insensitive powders ,as they contain additional additives which
aids in the problem .
One can try and stay ahead of the removal chore ,by cleaning more often . Please remember TOO MUCH CARBON can spike PRESSURE !.
Carbon ring in the rifle bore can affect accuracy, pressure and velocity. It's prone in cartridges with large case capacity and small bore diameter. Carbon ring is best identified with a bore scope and will appear as dark or cracked areas about 1-2" beyond the lede of the bore. If you're encountering this , say less than 150 200 rounds ,you're probably better off changing power or most certainly the charge .
I'll add one more tip ,patch your bore with Acetone or lacquer thinner BEFORE range time . Many people forget to remove Hoppe's or any other oil based bore protective . Because burning that ADDS to Carbon build .
Consider a combustible engines valve train or pistons . Carbon build up poor fuel quality or excessive oil burn .