I'm looking into buying a double rifle, and have come across a sound jeffery .450-400 3" hammer double.

How would it be to hunt elephant with a gun like that?

Is it very slow on the second shot - like a boltrifle?
I assume that one with practice would be able to shoot rather quick cocking the second hammer during the return of the recoil from the first shot?
I suppose that cocking both hammers at the same movement would be a bit avkward? Pull one at a time?

Is it a difference between the ones with an underlever, and those with a toplever?

I'd very much like to hear from those that hunt with hammerguns!