RE: Why not .280 Remington?
Since we have brought up O'Connor and Carmichel, I recal a colum written by the later about his meeting the former. At a party Carmichel was introduced to O'Connor and Carmichel proceeded to tell old Jack about a custom rifle he was having built. O'Connor asked him what cartridge it would be in and Carmichel thought he had better say .270 win. (really he was having it in a .280) A while later when there was no one around to overhear them O'Connor told Carmichel that if he was smart he would get his gun in .280 as Jack figured it had a lot more potential for handloading.
Years ago I picked a .264 win. mag. over a 7mm rem. mag. I don't think anything I've shot with the "6.5",would have known the difference.
Robin down under