The .30-06 will do it all. If you want more poop, then maybe the .338-06, or better yet the .35 Whelen. Flatter trajectory, maybe 25-06 or .270. The 7x57 Mauser is all anyone needs if they can shoot well, and pass up iffy shots. With anything based on the '06 case, you won't have to alter the bolt face, or mess with the feed rails. Then you can spend more on the things that really count, like a good barrel, and a well bedded stock. And ammo to practice with. Avoid the magnum hype if you can.