.700 Holland & Holland Nitro Express. It fires a 1,000-grain bullet at 2,000 fps, yielding an impressive 8,900 foot-pounds-- roughly twice the energy of a .375! Now that is a big bore.-Mike Schoby
I never thought elephant guns could get this BIG but I guess they do, I was impressed when someone showed me a picture of it... Definately a great self defense round!
There are a few pictures out on the net search for .700 or even the .600 Nitro Express!
[Edit] With the picture