Sorry have not started mine yet working on a few other projects got a Panther II , KV-122 , HL Leoapard 2 a6 and a M36 Jackson B1 to finish first I mite jump to it ahead of time .
You can buy from Tamiya USA the 122mm Barrel for it from the
JS-2 page.
Found this .
http://www.youtube.com/watch?v=WbJ1Fv6KlyM
Thanks
Jimmy