If a flat shooting 6.5 is wanted; look at the 6.5 Sherman. Either the long or short action. I shoot the long action and can get over 3300 fps with 140 Bergers. Compare that speed to some of the larger cases you are thinking about, and see what kind of velocity difference there is. The Sherman will come very close to matching the speeds of a 264 WM but with a lot less powder. My rifle maxed out with 64 gr for example. I only have a few hundred rounds through mine but barrel life is suppose to exceed 2000 rounds.