I stopped by Dixon's this afternoon; they usually have a ton of Green Mountain barrels. The rack was almost bare. Lots of Rice swamped barrels, but not a single 13/16" 40 cal GM.
I asked Greg about it, and he said that since Green Mountain was bought by Knight to make barrels for their rifles, they are treating the traditional barrels as a sideline. They have reduced the number of variations they offer drastically, and delivery times have gone way up. It can take them up to a year to get a barrel now.
He said Green Mountain still lists a 40 caliber 13/16" straight barrel, but they are back ordered.
Dale H