For me,a big 7mm with a quality 160 would cut a big swath....
That was exactly my choice for 20 years. Prairie dogs, coyotes, antelope, deer and elk, it never failed.
The "Magnificent 7" with 120-140g bullets will do anything a .257 Roy with 100g or heavier bullets will do in terms of trajectory. In fact the 7mm RM will do it a bit better (less drop and wind drift and higher impact velocity, albeit by a hair) while delivering an extra 300fpe on target. With 160g and 175g bullets the 7mm RM is an outstanding choice for elk and more than adequate for moose, delivering long range performance with recoil similar to a .30-06. And, of course, the 7mm RM can be downloaded to 7mm-08 or 7x57 levels if desired.
I'm not much of a fan of "one gun, one load" for all tasks, had enough of that the first 20 years I hunted big game. But if I had to go back to one gun the 7mm Rem Mag would probably be the sole survivor and I'd use multiple loads - 120g TTSX and 160g MRX would pretty well take care of things.
