Thats the 64000 dollar question. You know, I have killed a mule deer doe with the 75gr. speer flat point in a 25-35. Now that's a bit light for a big buck in full rut, but it can be done. Light bullets or heavey, fast or slow, shot placement and the animals demeanor are probably the most determaning factors. The favored caliber for me has always been the 25, A hundred grain bullet from the 25-06 at-3100 fps will stop in a deer's chest and do a lot of damage, the 117 under the same conditions would probably go clear through. I like the 270 with a 150gr. bullet for elk and have taken two cows and a bull with that combination. Not having worked seriosly with the 6.5's (I have killed one buck with a .264 Win mag) I can't say for sure, but it sounds like a good accurate choise. I would stick with the milder cartridges like the Creedmoore to avoid spending the rest of my time scrubbing the barrel. In a light rifle you can get great performance from the .270 or the 25-06 and not pay the recoil toll. For an all arround one gun caliber in the mountains the .270 is not a bad round,wide range of bullet weights and plenty of horse power. The optics you choose will give you the edge at long range, and you usually get what you pay for.