Thread: Throat Erosion - New Barrel

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?

I had something that seems similar recently in a set-back 6.5x47 chamber; 0.2mm (0.008") lengthening after 150 rounds, and initially with significant copper fouling when the barrel had always shot clean for 1700 rounds prior with the original chamber. Opened out the groups too — to a degree, but as we all know, a 6.5x47 never shoots more than half-inch even in the most adverse circumstances, so difficult to compare