I decided the only way to turn the completed front section would to be in a "socket". The section sits on a shoulder on the nose and is secured with a setscrew
turning ID of socket
Next up is some stock for the body of the tube. I found something that was close in ID and OD.
Boring in lathe.
Before I committed to having a overly long piece I had to cut the barrel lugs (and blocking lug for SBR)
modifying barrel (now extended) for blocking lug
After that the blocking pin preventing a FA bolt from going into battery
In socket ready to be turned
Tube section shrunk on
Complete tube in lathe and tacked. Although I do not recommend welding in a lathe, it seemed the only way I could hold everything straight without building a fixture. If you do this use a TIG, If any other process cover everything with aluminum foil to keep the spatter from damaging, most important is to keep the ground as close to the work as possible and never crossing a bearing.
parting to final length
starting to turn OD