At what point, as you move up the scale in terms of caliber and case size, do you start seeing a clear increase in performance on game from the creed?
What game and what is an increase in performance? You can move DOWN in caliber and case and get the same or better "performance" on "game" depending on variables. The cm is no better at killing deer sized critters than is a .260, 6.5x55, 7-08, Grendel, and many, many others. Possibly even a .270 Winchester or .223 AI. I can tell you for a fact that on a given day I saw a 7x57 with 140gr out perform a .340 Weatherby with whatever low weight Ballistic Tip Weatherby used to load. A pie plate entry with the .340 and the <100lb doe ran across a green field. 7x57 with Accubond on a 140ish lb buck that took a step and fell downhill about 12 feet. Which cartridge was "up the scale"? And I can give you similar stories about .270 Weatherby Mag vs 7-08, .260, .243...............
The 6.5 cm was not introduced to make up for the lack of killing power of any cartridge. Again, for deer sized game and probably up and down that "scale" some, there's plenty of chamberings that are no better or worse than their stable mates; the 6.5 cm being one. But I am hearing factories are starting to secretly load duplex powder loads with 1 to 2 grains of pixie dust between main charge and the primer for both the 6 and 6.5 cm. That's the real magic, not the headstamp.
