I know of the 700mm CZ barrels Talon Tunes has listed on his site, but they're .22.
There was also a place called airgunheaven over in Europe somewhere that sold drop in Vet barrels. Been a while since I've been to their website but I remember getting the impression that they were willing to work with the customer a bit on various options and lengths etc. Might be worth a Google search.
Ive had three Veterans rebarrelled, two were as Thammer suggested, 15mm OD Lothar Walther barrels, with correct threads on each end. The third was a 10mm OD Lothar barrel that the machinist made threaded brass endcaps for. Soldered at the muzzle end and CA glued at the breech. And then carbon fiber tubing to get the OD right for the scope tower clamps. Machinist in all three cases doesn't do it for a business-more of a favor for a friend, otherwise I'd pass on his info.
So, it can be done. Just gotta find a machinist or company capable and willing.
If I was in your shoes, I'd try a PM to Thammer first.
