What they aren't telling you about the 264mag is that to get this extra bit of velocity you are going to use a LOT more powder per shot AND you need to go with 26" bbl. The .264 pretty much died out because people discovered it was something of a fraud and never lived up to the advertising hype.

On the other hand, a 6.5/06 is far more efficient cartridge and WILL DO just about anything the 264 ever claimed. It's a very simple rifle for any competent gunsmith to make and will work on scads of actions. Cases are cheap and easy to come by as well. Very good honest rifle.