Glamdrig,
Your reasoning is sound as far as functionality is concerned. But having been in some tight situations I've dicovered that there really is a reason the double gun has become king in close quarters type dangerous game hunting.
If you've ever been in the tall grass with an angry elephant at close quaters you'll soon find out why the double gun is king. Same goes for buffalo, leapord, lion, hippo you name it.
The whole point of a double gun is this it is capable of firing an adequate calibre for knocking down the largest of dangerous game. And it is capable of delivering a second shot faster than any other rifle configuration on earth when using an adequate caliber.
While it is true that in the days of lore many pros/ivory hunters used single falling blocks because that was what was available. They were replaced by turn bolts and doubles as they became available because they are a better tool for the job.
I've been in two situations were I was wishing for the fast handling characteristics of a double. Once on a gut shot buff in the tall grass and the other time with a particularly pissed off cow elephant that I stumbled into also in in the grass at about 25 feet.
My current heavy rifle is a custom built stainless mod 70 in 458 lott. A very adequate rifle and caliber set up. But my double .470 NE arrives next week
I'm not saying not to use what you want, I'm just saying that in a tight situation I like to have more than one round. (And I want more power than even a hot 45-70) The 5000 ftlb magic number has alot of validity....And larger bore diameter/ heavier bullets do make a difference on knock down on thick skinned dangerous game.
Top ten reasons to own a double.
1. Much of the stuff you've heard about doubles and there "weak" action have been solved with modern meturolgy. They really are quite stout now days. (Note never use high pressure rounds in a double .458 win + double=BIG TROUBLE! EAA stopping rifle included!)
2. Think of it as two single shot rifles tied together (at least in one with two triggers/hammers and a non automatic safety) so if one rifle dies you still have the other barrel.
3. Automatic ejectors makes it actually faster to shoot four rounds than a turn bolt. (I know... but it's been proven time and again.)
4. Nothing on earth handles faster than a double rifle that is fit correctly.
5. Nitro express rounds while not any more powerfull than current shorter rounds are so long and fat they just look more powerfull.
6. Most likely you'll be the only kid at the range to have one.
7. You really didn't need all that money in the bank anyway just sitting there collecting all that pesky interest.
8. At $10.00 a round your not just shooting your helping increase the GNP.
9. Chicks dig it.
10. Cool factor is so high that sun glasses are required at all times when carrying it.