760/7600 rebarreling is touchy... It is not a simple thing to set it back a thread to ensure headspace is correct... It must be measured and done precisely the first time.
An old guy in Oregon was the go-to guy for years, but he dies quite a long time ago and I have not heard of anyone else that specializes in them...
I have a 7600 which is now a 35AI done by West (the deceased guy in OR) and it has a little excess headspace, which is no big deal for a reloader...
