Licensed to Kill, that is good, clear, information and advise. I'm somewhat hesitant on the shooting it out idea, but probably just because of the unknowns to me. Attached is a picture of another gun, not mine, showing the face of the plug. Mine must be similar. It seems like a piloted end mill or similar could be made to work by constructing the guides for the bit on a lathe, which I don't have. Your thought about gripping only the barrel being worked on at the time, makes perfect sense. I had wondered about the torque that might affect the rib/other barrel solder connection.
![[Linked Image from i.imgur.com]](https://i.imgur.com/C2a4eeN.jpg)