6.5 CreedMoor is the 1st cartridge/chambering post-ubiquitous LRF that's had people who actually shoot, on both the rifle and ammo side, sit down, put their heads together, and design the rifle (chamber, mag box, twist rate) to meld with current projectiles and forward looking to where projectile R&D is headed.
Previous to that with the exception of Rem long-actions and to a lessor degree Sako, rifle manufacturers put 0 thought into how a chamber and a mag-box might correlate. Rem and Sako didn't get it right so much out of thought as much as by putting everything "long action" on the same 3.6"++ magazine mostly for the cost savings of continuity.
Case in point, there's never been a Rem 700 nor 40x chambered in .308 from the factory that would allow you within .25" of the lands while still retaining a short enough COAL to fit and feed from the internal (or removable) box magazine (single-shot followers don't count here).
The CreedMoor, PRC, and ARC have all taken into account and purposely produced chamber dimensions, twist rates, and magazine confines that allow one to experiment and expect excellent results with available and future components.
It's not "magic", it's forethought.