Double or bolt..? What calibre..? I am thinking game like elephant, rhino (perhaps not that relevant), hippo and cape buffalo..
I will argue this: - Either a double rifle in .600 or .577NE OR a Mauser actioned bolt rifle in .500 Jeffery..
What do you think..?
Hands down, ballistically, coupled with weight of rifle, and recovery time to get off a second shot, the .577NE is the stopping rifle king. Based on the aforementioned criteria, its superior to the 600NE and 700NE.
In a magazine rifle, its pretty hard to argue with the 500 Jeffery. Again, weight, recovery time for subsequent shots, feed reliability, bullet weight, its a professional's rifle. It's slower than the 577NE for a second shot, but it has a third and a few of them a fourth shot. Some professionals that cull elephants prefer more rounds over more stopping, selecting the 500J for that reason.
Neither of those guns is needed for me as a non-professional, but I respect them for what they are, and if I was browsing for a 470NE and I found one of the above for the right price, I would certainly consider owning a professional's tool if I could shoot it effectively.
For a client, it's pretty hard to top the 375HH, 404J, 450-400NE, 416Rigby, 458WM, and 470NE. All very controllable guns in the hands of a non-professional for the tasks they are designed. (killing game, not stopping charges)