I have a pair of 243’s that have accounted for 14 elk—all them with 100g Pt’s. Mostly in the hands of youngsters. Regardless, there’s not much big game hunting a 243 can’t accomplish with a stout bullet.
When it comes to critters like elk it’s the bullets we choose rather than the cartridge.
I would plan on being equally prepared to take shots at 60 yds. A rifle that handles well, carries easily, and a scope that allows a wide FOV will net a lot of elk.
In 35+ years of guiding I’m not aware of any outfitters (assuming you’re going on a guided hunt) tell a client to be prepared for...