Good luck. There absolutely is no best caliber. Not for elk or anything else. You need a rifle with enough power to do the job. The rifle is not going to do it by its self. Its what you do with what you have that will determin your success or failure. Every caliber has its strong points and weak points. If you are a good hunter carring anything from the 270 on up, you will be successful. The best will be argued forever, with guns, with cars and even girls. This will always come down to a matter of opinion. Therefore when it comes down to it you will have to make the choice and then live with it. You have some good advise here. Now do your homework and pick one. I have never missed an oppertunity with the 30-06 and 270 class rifles. That is because of the way I hunt and not what I used to kill the animal with.