Just for the heck of it I'll throw in my two cents, although its probably the same information just stated differently. It's actually pretty simple, don't just go by what someones says at the gun counter of your favorite store. There are a lot of opinions from hunters who are just repeating what they learned growing up, without any real knowledge of what happens when a bullet strikes an animal. Luckily most deer bullets out of most deer guns will kill just fine. Growing up in New Jersey and Pennsylvania I've seen too many hunters take 80 yard shots with buckshot and 300 yard shots with 35 Remington's, and you'll never convince these hunters that what they are doing is wrong.

You are out here on the Internet trying to research the best way to be a conscientious sportsman, you won't go wrong by following educated advise.

I also have had the opportunity to speak with representatives from several bullet manufacturers. Like what has been stated here, you need the proper bullet for the game that you are hunting. When bullets are designed they have to take into account what type of hunting will be done with each particular bullet. They also have to consider the velocity differences between the various calibers that it might be loaded into and what distance that caliber will be used. The reason that some people have deer run farther with magnum calibers is that these bullets are designed so that they won't blow up at high velocities when used at close range. Couple that with fact that deer aren't that big and you get a bullet that zips through without much expansion or expending any energy. They told me that it's actually easier to design deer bullets for a .243 and a 30-30. These are two calibers that most people wouldn't even consider using for larger game like elk or caribou. Not many calibers give the perfect mushroom like a 30-30 does, because it's easier to design a bullet when it's mainly used on the same animal at similar ranges. What you can't do reliably is design a bullet for a 300 mag that one person will shoot a deer with and another will shoot a moose or grizzly with.