I have everything from .223 to 458 Win, with lot's of overlap in between. If I was to go with the thinking on this thread, I might choose the .308, the .300 Win and the .458 Win.
But after a bit of thought, I am going to fall back on what gets shot the most by me. Discounting the 22 RF's and the handgun cartridges, I most often grab for one of several 30-30's as a light shooter. In the medium caliber arena, I often find myself shooting a MarkV Custom in 7mm Weatherby. And I too, dismissed Weatherby's until I bought and used a few of them.
Last but not least, for me in this day and age, I usually grab my Browning Safari (The old Belgian Safari) in 300 Win Mag to shoot anything bigger. I know the last two overlap in a big way, but I like them both too much to stop shooting either one.
Then there's the 458, for those things which can and will bite and stomp me into buff stuff. But there are no elephants on my menu and I'm getting too stiff in the joints for a buff . Should that change, I am covered.
And to address the concern of a 400 yard shot presenting itself, my first choice would be to use my feet. A choice most of us should consider. That said, even though I have practiced at 400 yards and the 7mm or 300 would be fine. I for one, still enjoy the HUNT in Hunting.
Thanks
Larry