I love these questions because sometimes they genuinely seek information but mostly, under careful consideration, don't make sense. If you can afford the time and money to hunt both antelope and elk you can purchase guns to do both. How many readers on this site own only one gun? Why limit yourself? 6.5 CM is great for antelope, something larger for elk, maybe even larger for brown bear and if you're going to Africa, certainly a .375. Then there's prairie dogs and coyotes. Not to mention LR targets at 1000 plus yards. I started 50 years ago shooting jackrabbits with a .300 Wby Mag, and also shot moose, caribou, elk, deer and coyotes; but couldn't recommend this to everyone. 30/06 is a great all-around cartridge but recoil may be too strong for some. I enjoy a 338 Lapua Mag now but it is also too much for small game. Pick something relevant to most of your shooting then buy/build something for the rest of your shooting interests.