RE: .264 mag.
It was a good caliber but ahead of its time. I should say ahead of its powders. When it came out there were not many good slow burning powders for it. That is no loonger true and it would be a fine long range deer antelope and elk cartridge. As mentioned above the best if not only way to get one would be to rebarrel a LH 7MM Mag. It may be a worth while conversion but you would gain nothing over the 7 Mag as is.