RE: 6mm Remington and elk
"Marginal" and "Bad" are a matter of geometry. There's not much of a "margin" at 200 yards on an elk quartering away. A couple inches one way and you miss, a couple inches the other and you've gut-shot him. A little low and his front leg's gone, a little high and you hit him superficially in the shoulder. No amount of firepower's going to correct that. And, "bad shots" are often as much a fault of poor judgement in taking a shot with too much "margin of error"as they are lack of skill.
Rely on whatever you need to. I'll rely on good judgement, marksmanship, and stalking/set-up all day long. And, if it really WERE necessary to carry a magnum-whatever into the field for elk, what the heck are all those guys (and gals) doing out there with big handguns,bows, arrows, and traditional muzzleloaders?