4. .308 Winchester
There's a reason Jeff Cooper selected the .308 Winchester cartridge for his conceptual, one-rifle-for-the-world Scout Rifle. It will handle beasties up to 1,000 pounds without shoulder slamming recoil. Ammunition can be found almost anywhere, to include gas stations and hardware stores. It can be had in a very light rifles, precision rifles, a semi-automatic rifles, single shot rifles, lever action rifles, and pump action rifles – if anyone still cares about pump action rifles. Because it is shorter, kicks less, and fits in more compact and lighter rifles, the .308 is the new .30-06.