Lot of choices out there, when I run the contenders in my mind I come-up with .257 Weatherby (26-inch barrel), 6.5-06, 6.5 Remington Magnum (24-inch barrel), 270 Winchester (24-inch barrel) 270WSM (24-inch barrel), and the 7MM Remington Magnum (24-inch barrel).
I quickly dropped the .257 Weatherby because it was the bottom of the energy curve.
I dropped the 6.5 Remington Magnum because it is hard to find them with 24-inche barrels, and new brass is very pricy. The case has the same powder capacity of the -06.
The 6.5-06 is good choice because commercial cases are manufactured, and cases can be made from .270 Win, .280 Rem, and -06. It has a long neck and heavy bullets do not use up a lot of powder space.
I have killed a lot of deer with the .270 Winchester and most of them have been at short range. I have never shot at a deer at 500-yards. I have had the opportunity but felt I was better off getting closer, or passing. Five hundred yards is not in “my” skill set.
There is a ridge that I hunted forty years ago that to take a buck on it my best bet was to work by way down the ridge to the North and take a long shot. I used 130-grain bullets at the time. Today I would use 140-grain bullets in the .270 Win. or the .270WSM.
If I was to return to the ridge or long range location I would take my 7MM Remington Magnum. I would select the 160-grain Speer Spitzer, or 154-grain Hornady Inter bond. For long range shooting the 7MM Remington Magnum with 160-grain bullets offer good penetration, flat shooting, and high energy with less recoil then a .300 Magnum. In tough broken country I have found exit wounds of high value even with a heart-lung shoot because two holes pump more blood then one hole.
How did I come up with my list? First my brother has or has had the .257 Weatherby, 6.5-06, and the 6.5 Remington Magnum. I have had a 270 Winchester, and a 7MM Remington Magnum. There is not a bad one among them for most hunting situations involving deer and antelope. When large game comes into play I think it favors the 7MM Remington Magnum.
If I was going to buy a new rifle today most likely it would be a 270WSM.