They both have a 2.5" total case length. Why? Because that was the same basic length cases that worked well in the standard 30-06 based actions, which were plentiful and could be had for very reasonable prices compared to the true magnum length actions available in the late 40's and early 50's. They both were preceded by many wildcats that were basically the same; Ackley, Frank Barnes, Mashburn, Apex, and Durham all developed similar cartridges just to name a few. But if you want to follow it back to its logical starting spot , you have to go back to 1912 and look at what Holland and Holland was doing at the time. Yep, 1912, long before Winchester or Remington had a clue they wanted or needed a 2.500" magnum case in any caliber, Holland and Holland introduced the 275 H&H magnum. If you can dig up the case dimensions on it you won't have any trouble figuring how the .264 and 7mm mags got The 195 Berger out of my