Question:

Thinking back to the old-time ivory hunters who used single-shot rifles (Selous and his .461 Gibbs), would you consider today's modern single-shot rifles like the excellent Ruger No. 1 in the appropriate calibers a viable dangerous game rifle? I do understand the user would have to devote the proper amount of time in practice, both for shot placement and fast reloads.
 

Answer:

I love single-shot rifles! Single-shot rifles make you think about putting the first shot in the right place--in other words, you tend to shoot better with such rifles. I also love Ruger No. 1s.

When I was still involved with the training of PH's in Zimbabwe we used to put them through a shooting test--three targets set at 30, 20, and 10 paces. The test was to get off 6 well-aimed shots--at 30, 20, 10, 10, 20, 30 as quickly as possible.  Turnbolts were allowed to load only 3 cartridges, so a reload was required.

Over two decades I saw this test shot a couple of hundred times in all calibers from 9.3x62mm all the way to the .500s, with all types of rifles. Believe it or not, the fastest it was ever shot was with a Ruger No. 1 .375 H&H!

The secret was that the learner PH had 5 elastic loops sewed onto the top of his right shoulder so they held 5 cartridges that lay horizontally but pointed rearwards.   

He was really well practiced and could shoot, eject the empty cartridge case, reach across, slip out another cartridge, load it, and fire, all without lowering the Ruger from his shoulder. It was an impressive performance.

So yes, I would not hesitate to take a client dangerous-game hunting if he chose to use a single shot rifle-- but with the proviso that he was well practiced with getting it reloaded quickly.  

I do not think you need 5 cartridges on your shoulder; a couple will do.  Have some dummy cartridges made up with which to practice reloading quickly but always remember-- it is the first one which counts.

The .375 H&H wins hands down as the best African all-rounder, but I must say I do like the idea of a Ruger No. 1 in .450/400 NE. Scoped with a low powered 1-4X or 1.5-5X and a combination of good 400-grainers it will make for an effective African all-round alternative.