Hello everybody just want peoples opinion on my issue. So was cleaning my tikka after shooting 40 rounds for the first time. I used wipe out and soaked and also g96 and also clp 2000 foam. Many many patches and also bronze bore brush with bronze core. It made the whole barrel spotless and immaculate. However i noticed there is a circle of crud where bullets comes out the neck of case the carbon ring I believe see pic. I tried scrubbing so much other than spinning the brush on a drill which I do for my cheap rimfire. What chemicals are there that is strong enough to remove this ring.