Have you tried the Accurate Shooter forums? There's quite a lot of talk about the 6BRA on there and someone can probably steer you in the right direction. I know Alex Wheeler is chambering up a few of these.
Small world. I've been following those threads and called Alex. He is 6-8 weeks backlog and will not put me in line for work until my action arrives. He also wanted $800 for the barrel and work which would be considerably more than I've ever spent.
Being in AZ our long range matches are at lower altitudes and reasonable temps during the winter so it's high season for me right now, thus not wanting to wait that long.