What a clusterfuuck. If you go through and figure out what the question really is, you can then go through and find potentially relevant answers! Nice!
I think it's this: He has a Howa 1500 action in hand. He has a new Christensen Arms 6.5 CM Remington 700 Barrel in hand. He wants to put them together.
No go. Rem 700 threads are 1 1/16" x 16 tpi and the Howa action is threaded metric.
Yes, however, it's doable on a long action Remington 700 with the correct boltface, and a short action too with the correct boltface, assuming you use a standard Remington recoil lug and it all goes well without lathework to achieve correct headspace, although not always does it work smoothly for SA cartridges in LA actions regarding feeding the SA cartridge, but, thankfully, it does seem to be okay with the wonderfully designed 6.5 Creedmoor (note, no 'e') cartridge, in the Remington 700 LAs, BTDT, so, indeed, without buying another compatible barrel for the Howa or a Rem 700 action, for the CA barrel, Idaho is sol, but by golly, Remington 700 two-piece scope bases work on the Howa 1500s so there is that, and double thankfully neither of these actions discussed are CRF or there'd potentially be, or surely there would be more fubar involved. LOL 😁
All in good fun.
