Steve, just did one for a pal - 1.060"x16TPI - don't recall the length - just took measurements of action.
The Bergara (a B14 model .22/250) has a lot of looks, but it's like a dud woman - really crappy: barrel tenon: bolt-nose contact; only one lug @ about 70% contact; needed bedding (about 0.030 dial indicator movement at fore end); etc. I shaved some clearance for the bolt-nose: BBL tenon face, lapped the lugs, and cut a good crown - it still is about a 1.0" 3-shot grouper! Can't see any reason for the fake cone . they got the make-up a little heavy there.
So, I got a Wilson BBL, and Tom came down - we made him a 6mm Creedmoor - his initial F-F loads were all better than the best via the factory .22/250 BBL - .75" and under. Still not great, but much better - perhaps he'll get 5/8ths" & under with formed brass.RG