Adam, Good info on that brush! link: http://www.brushresearch.com/brushes.php?c2=183
I will say I bought one of the Shilen Barrels to just check them out and the measurements came out with CBtO @1.680, right in line with yours. The OAL was 2.251. I didn't notice any marks but when I fired it had cycling issues. I called them and spoke to some guy about the issue and he said he knows nothing about gas ports or AR's. They just make barrels and said to call someone who might know. I called a guy and got an answer that helps and resolved my questions so the CS Sucks.
I will say I put 3 Lilja barrels together today and they all test fired on round one, not feed issue and I didn't notice the scuffs, my bullets went forward down range.
I will say I bought one of the Shilen Barrels to just check them out and the measurements came out with CBtO @1.680, right in line with yours. The OAL was 2.251. I didn't notice any marks but when I fired it had cycling issues. I called them and spoke to some guy about the issue and he said he knows nothing about gas ports or AR's. They just make barrels and said to call someone who might know. I called a guy and got an answer that helps and resolved my questions so the CS Sucks.
I will say I put 3 Lilja barrels together today and they all test fired on round one, not feed issue and I didn't notice the scuffs, my bullets went forward down range.