I'd recommend using the stainless action/bolt unless you want the blued action cerakoted. Since the stainless action is a standard bolt size I'd look hard at 6.5 Creedmor, 6 Creedmoor, or even 22 creedmoor.
If you're going to use the magnum bolt face - 6.5 PRC, 7 SAUM. 6 UM or 6.5-7PRC if you...