Anyone who has killed a moose with a .243 will strongly disagree with those who say it can't be done, as will those who have killed moose with a .22 centerfire. But the .243 comes with so many provisos when a big animal is the target (short range only, broadside only, no rear quartering shots, stay out of the shoulder etc, etc, etc) it certainly doesn't meet my definition of an appropriate cartridge. IMHO, a big game cartridge should have a reasonable expectation of killing the game animal with a single shot, from any shot angle, within the range limitations of the rifle, cartridge, and marksman. With the possible exception of the .25/06, I believe the various 6.5s describe the lower end of practical big game cartridge spectrum when moose, elk, and bear are the intended targets. I personally think that a .243 performs optimally on game of about 100 pounds. Yes, this is arbitrary, and yes, if I was packing my .243 I wouldn't pass up a shot at a 300 pound seal, or a 350 pound caribou, but when you leave home with the intent of hunting a bigger game animal, I believe a larger bore is more appropriate.