You got to borescope. After a 1 day match the carbon ring was all the way around the throat and if I fired 50 more rounds, the ring would be big enough to contact the bullet, stripping copper off of it if I chambered a round and then extracted. The powder is dirty, the dirtiest powder I have ever used. But it also gives great results with single digit ES SD numbers on 20 shot continuous strings. Now that I know of the problem I take steps to keep it from going to far