Of commercially made modern double rifles, the Krieghoff is very good and their rimmed .416, 'tho fairly new, is very effective for moose, bear, cape buffalo and, even elephant. Mike has the recoil equation right, it depends on what a rifle weighs. A ten-pund .416 should be manageable, assuming the stock design is right, not too much drop.
The Krieghoff's have an unusual safety that works by cocking (or decocking) the internal hammers. I've not experienced it and you hear varying points of view. If you are new to doubles, shotguns or rifles, you won't care. It's a novel way to solve the problem of safe carry and of quickly bringing the gun or rifle into action.
Depending on the bullet you use, you can shoot much smaller animals. A generally true rule is that, if you, handload, you can use a bullet 3/4 the weight that the rifle is regulated for and the barrels will still regulate, if a little higher on the paper. So handload 300 grain bullets, of which there are many and good ones and take it out for moose, bear and the like, if you don't want to use the 400 grain bullets normally in factory ammo.
Now, the next level up would be the various .450s and .470s, that begin serious, stopping rifle dangerous game calibers. They start at 10 lbs. 10 oz or so. After that is the .500 Nitroexpress that should be about 12 lbs and will still do some thumping.
Pick up a copy of the 2nd edition of Graeme Wright's book on Double Rifles or something similar to get a good start on the subject.
Regards
