"Elk can run off with a poorly placed shot from a magnum"

VERY TRUE! but they will run just as far or further "with a poorly placed shot" from any LOWER POWER CARTRIDGEs so whats the point!
accuracy in shot placement and a good understanding of the games anatomy are mandatory, to get good results.. I see a much higher percentage of well hit ELK run a short distance when hit with the smaller calibers than I see of those hit with the heavier calibers, and let me point out its NOT just MAGNUMS that hold the advantage here, a quality 225-250 grain bullet from a 338/06 or 35 whelen OR EVEN A 358 WIN thats basically a necked up 308 win, does a remarkably effective job on ELK, as will a 350-420grain 45/70 bullets when placed correctly