I have a Hawk Hill Customs 6mm Dasher barrel for sale with the following specs (if I leave something out please ask):
26" length
1-8" twist
Chamber end diameter 1.255"
Muzzle end diameter .910"
Threaded 5/8x24
Weight 5.0 lbs
Came off a Surgeon action but assuming good to go for any 700 or clone...