The 458 Weatherby Magnum and the .416 Remington we the answers to questions that no Big Game hunter ever asked. The British line of Big Game Rifle Cartridges were all designed to be suitable for double rifles and the afore mentioned cartridges just added unnecessary additional rounds to the big bore selection. There's not an animal that has ever lived on this planet that couldn't be taken down by British Nitro Express rounds. The .458 WM and the ,416 Rem. were surplus to requirements before they were even made. JMHO.
Harry
With all due respect I am going to differ with you. Double rifles, as we all know are expensive, and really only of use for hunting dangerous game at short ranges in places like Africa. The American hunter who purchased a bolt action Weatherby or Winchester did so for multiple reasons in addition to cost. Most American hunters are very familiar with bolt action rifles as they are the predominate big game hunting rifles here. The 458 Winchester and 460 Weatherby are rimless and far more suitable to bolt action rifles than the rimmed nitro express rounds. These rifle are also suitable for dangerous game such as Grizzly Bear so would be useful to the hunter here as well as in Africa.
When someone can buy something comparable to another item and it costs less, is more versatile and the user if very operationally familiar with it it's usually an easy decision to make.
I just checked and the Model 70 Winchester in 458 Magnum is still available brand new for under $2,000.. What would a British double say in 470 Nitro Express from one of the few remaining makers sell for at this time?
Here's a used John Rigby that's currently for sale that should meet your criteria:
http://www.gunsinternational.com/JOHN-RIGBY-CO-Sidelock-Double-Rifle.cfm?gun_id=100340486Jim
