Thread: Throat Erosion - New Barrel

Originally Posted by Puffin

Your original reference CBTO measurement for just touching might have been influenced by some roughness in the finish of the cut of the leade, that has now been smoothed out after some shooting and hopefully has stabilised. The improvement in copper fouling might support this idea?

Almost certainly the cause of the large initial jump in CBTO distance. Not uncommon to see then the CBTO measurements settle down dependant upon the cartridge and load being fired.

Carbon build up/ring gives the opposite to what the OP has posted ie gives reduced CBTO distances. That's not to say the carbon and maybe copper isn't the cause of the accuracy drop off. The carbon build up also makes it virtually impossible to get repetitive accurate CBTO measurements if using the Hornady case method.

Best to deal with carbon at each clean rather than letting it get a hold.