Barrel threading, how to do it?

[RobF]

I suspect such a lathe would be a very specialised and expensive bit of kit?

I don't do facebook, but if it can be viewed without having to log in?...any chance of a link, please?

I'll see if i can find them. The problem with Facebook is stuff gets buried and lost and is pretty hard to search. It's not really concerned with longevity.