Don't be too sure, elephants are pretty big!
I was watching a documentary where they were culling some elephants, the ranger was using a FAL, he killed about 4 in a couple minutes, all brain shots, in the clear, bang flop.
The 7mm is good enough for elephant but brain shots only. An elephant offers a larger traget for a brain shots than say a buff, also elephants generally charge straight on, make easier targets to spot since they're taller and generally in more open bush. A buff on the other hand moves more erratically, lots of time from cover, and ois a smaller tougher target with almost no brain.
Ross Seyfried apparently tried shooting a buff in the brain with a .22mag semi auto, all ten shots dead centre and the buff just looked at them before they dispatched it with a bigger gun.
Shot placement is key, but animal size and toughness does make a difference so I wouldn't compare what guys did turn of the century hunting elephants with 7mm even though it is intriguing. For nasty animals I'd rather be safe and carry a bigger gun. For bear I'd feel better with a 45-70 than a .308. But for NA you could get away with a .308 for almost everything even if it is streching it a little. A short compact .308 scout rifle could do it all, but then so could a .375 Ruger Alaskan with a little more of a comfort zone.





















































