Caveat: I'm not saying the average shooter/handloader can reliably prove the difference.
What I consider to be "accurate," you or someone else might not. I am not a competitive shooter, I just hunt, and the ranges at which I get to shoot probably would top out at the 400-500 yard distance. So, a few hundredth's of measurement in a group that my rifle shoots is not going to mean much. But, it most certainly would if I was shooting in a match.
The 308 has been one of those cartridges labeled as "inherently accurate," yet I've seen some rifles chambered for it that were not. I've also seen some that were, so my thoughts have always been that good accuracy, for me, starts with the rifle, then the ammo, and not the cartridge.
I have a 6.5CM in a cheap Howa rifle, and it is among my most consistently accurate rifles. I don't know if it's the rifle or the cartridge, and to be honest, in my case it doesn't matter. As far as the 6.5 goes, there is a lot of very good components to choose from when working up a load. That helps a bunch.
