When I started hunting I carried a 760 rem in 30/06, on the advice of several experienced mentors, it worked great, but I was under the impression, that I needed a magnum caliber as the first couple elk I shot failed to instantly fall over when hit,
I upgraded to and I have mostly carried a 340 wby mark V or a sako 375 H&H carbine,
these did not kill any better but you darn sure got a more noticeable reaction when you hit game! (they became my trusted companions for decades.)
I have had a remington 7600 in 35 whelen as a shared hunting camp back-up rifle available on many of the trips to hunt elk, and its saved the hunt for several guys over the years when for various reasons their rifle stopped functioning.
the more experience I got the less I worried about the rifle being used, simply because Ive seen everything from a 257 robert's BLR to a 458 win ruger single shot, used successfully, to kill elk.
I personally trust, and prefer to carry the .338-.375 caliber rifles , but Ive seen that anything from .257 to .458 works if the guy carrying its knows how to use what he has in his hands.
I've just seen too many elk and big mule deer killed very dead with a 257 roberts, 6.5mm swedish mauser , or 308 win, to think you need a magnum, or guys using a
444 marlin, 45/70 or 458 win to think you need the flattest trajectory available