The barrel is thread into the receiver and it is tighten tight. I tried a barrel vise and made a special wrench for the receiver. I could not get it to budge. I quit before I twisted the receiver. Years ago when I re-blued it, I'm thinking I saw a retainer nut used to lock the barrel to the receiver inside the receiver. I maybe wrong, I could never find a schematic that showed such a retainer and I just look again all my books when I saw your post. They may have tighten them like the 1917 Enfields which I have gotten apart. Anyhow, Why do you need to separate the barrel from the receiver?