The theory from many years ago was that you needed a minimum of 1800 ftlbs at the target (animal) for elk.

If you are a trophy hunter, I'd highly recommend nothing less than a .300 Win Mag if you can carry the weight and handle the additional recoil. Use 180 grain top quality bullets (example: Nosler partition, Speer Grand Slam, Woodleigh, etc.) I have shot several with it and it does an awesome job.

I have used a 30-06 for everything from blue grouse, turkeys, bobcat, coyote, jackrabbit, antelope, whitetail, mule deer and of course elk. It does an excellent job. It is a rather heavy also Win 70.

Now I am going to carry a .308 Kimber (plenty of power to 300 yards and very light to carry).

If you hunt heavy brush and only to 100 yards or so, almost anything will do. If you might need to stretch your shots, use something that has plenty of power out to the animal. If you are only a meat hunter, you may not need the power.

As Robert Ruark said in his great book "Use enough gun" and shoot it in the right place. You will always regret it if an animal is lost.