I ran some numbers on wind drift figuring that it's the great variable and for powerful cartridges in any bore from .25 thru .30 cal they are all about the same with comparable bullets be they SBT's, MK's or whatever!
Of course the bigger the the bore the more powerful but there are trade offs on recoil to be sure.
I happen to have a 7mm WSM
in a M 70 SS Classic and it's very accurate and now sports a Farrel elevation base and a Leu 4.5 X 14 Tac scope. This rifle is now in "coyote mode" with that scope.
I have another in the works and it will be on a Montana SA in 270 WSM with a 24' tube. These rifles will have premium barrels and in the case of the Montana a laminated stock.
I did not opt for the 6.5 X 284 because of it's limited power. Sure enough you say 500 yds but sure enough if some critter is way out there then why not a 264 WM?
If it's just target shooting of course a 6mm will cover the first 600 yds but they don't hit hard enough for me way out there.
Get whatever you want and use it to your best ablity. That's what it's all about.