RE: ELK CARTRIDGE?
I worked with an Elk herd at a major zoo for 5 or 6 years and have a fair amount of experience with these animals. They are physically larger than most folks think, especially the bulls.
For my money, the bigger bores/bullets are better for taking Elk, providing the hunter can shoot accurately. Smaller bores will kill Elk, and the term "right bullet" or "proper bullet" is often used by hunters using these rifles. Having "rubbed shoulders" with 30-40 of these animals on a daily basis, I went to the .375, if for no other reason than to insure a humane kill. If you're looking for opinions, I'd say stay above .30 caliber and you won't regret the choice.
Most important is bullet placement. We killed selected (sick) Elk cows with a Ruger 10/22. They were shot through the top of the head with a .22 LR solid while putting their nose in a bucket of carrots. Lightning would not have been quicker.