The bottom-line stark reality is that unless you are directly involved in a follow up on wounded dangerous game, or in a Leopard blind, or in an up-close-and-personal stalk on DG at 30 yd, etc. there is no reason why you should have a round in the chamber.
Now to explain a bit this terminal statement
Yes the best safety is between the ears; yes muzzle discipline prevents safety failures from having catastrophic consequences; yes a bolt-mounted firing pin-blocking safety (whether vertical like the Mauser flag; horizontal like the Winchester 3 position; lateral like the Weatherby, etc.) is pretty reliable; yes, yes, yes... but the bottom line is why would one carry a loaded hunting rifle (i.e. a round in the chamber - as opposed to a munitioned rifle i.e. rounds in the magazine) unless there is a need for imminent shooting? A hunting rifle simply does not serve the same purpose as a concealed carry weapon or an infantry CQB weapon.
There is no real NEED to load one's rifle until one is about to get on the sticks, or in otherwise shooting position. Personally, I always ask the PH to witness my empty chamber and hear my dry firing "click" after killing an animal, and ALWAYS
before getting in the truck. This is out of both practical safety and courtesy, and when I have my boys or girls with me, we cross safety-check our rifles. Old military habits die hard
I thought the only exception would be my Krieghoff double, with its independent cocking mechanism, but my PH in Limpopo still asked me to carry it without ammo in the pipes until we started an actual buff stalk. I certainly understood and was happy to oblige... Nothing scares me more than a loaded double with a traditional shotgun safety on someone's shoulder...
I have (so far?) in 40 years of hunting never been in a situation where not having a round in the chamber has caused me to miss an opportunity. I have either stumbled at 30 ft into animals I had not been aware of and that bolted explosively on me, in which cases there either was no shot anyway, or, like in a reload after a first shot, a quick handling of the bolt was fast enough; or, during successful stalks, I have always been able to load quietly enough that animals 50 or 100 yd away did not hear it.
As to bolt open, it is an old practice in many places, including Africa, to carry a rifle with a bolt half open. On many Mauser 98 and myriad clones, ZKK 602, CZ 550, etc. there is actually a half way point where the bolt starts to close but is not cocked, and it is maintained in position by the pressure of the striker spring before it is fully compressed by closing the bolt down and forward. Is it safe? Well, the rifle certainly cannot fire in this position, so the answer ought to be yes, right?
The challenge, however, is that safety is most likely to be required not when everything goes right, but when everything goes wrong. Is it possible to trip and fall precisely on the right hand that holds the rifle with bolt open, get it closed accidentally under the weight of the body over the hand in the fall, and getting it fired if the trigger hits a rock or a twig? I guess it could happen... Is it safer than a firing-pin blocking safety? Probably not... Are we discussing far fetched scenarios? Yes... But in my experience (more military than hunting related) accidental discharges happen either out of sheer stupidity, in which case they are negligent discharge, or through an accumulation of indeed very far fetched and improbably events...
Empty chambers have never killed anyone. I default to this one...
Just my $0.02...
A parting thought, which I am sure will get me plenty of flak
is that I do not systematically default to the judgement of the PH, whether in Africa or anywhere else. I had one PH younger than my kids who clearly did not have half my shooting/hunting experience and who made blatant error of judgments; I have heard more PHs than one would care to hear say things entirely false re. rifles, ammo, etc.; I have seen one PH be blatantly unsafe in his gun handling; etc. ... and I have, of course, seen PHs who clearly mastered all aspects of their job better than I could ever hope to do myself... The point is that if an accidental discharge happens and somebody gets hurt or killed, your PH will not be the one in the accused box, you will...