I have a Miroku O/U shotgun, single inertia set trigger with safety also serving as a barrel selector. Firing it with snap caps, pushing the safety directly on and off again after 'firing' the first barrel does allow the second barrel to fire i.e. in the case of a misfire the second barrel can be fired with a quick flick of the safety, the barrel selector doesn't have to be changed. If this system was on a double rifle then then it would only be a fraction of a second to bring the second barrel into play.

Apart from all this I imagine that even with second triggers or mechanical set triggers, the shock of having a misfire either through a faulty cartridge or mechanical failure of the lock or trigger mechanism would take some time for the shooter to digest and to overcome and get the second shot away 'effectively'. I say effectively because in many cases a second attempt after a failure is most likely going to be rushed and not as effective as it should be.

The reality today is that hunters in Africa are backed up by competent professional hunters, a charge is relatively rare, the majority of hunters use bolt guns anyway and there are not droves of them arriving home in body bags. The day of the lone white hunter shooting hundreds of dangerous animals relying on his own ability and guns to keep him safe are long gone and many of those hunters used nothing but bolt guns.

Those who think they need a double trigger double rifle to keep them safe in Africa are dreaming but there is nothing wrong with the dream and nostalgia to hunt with fine doubles just as many of us enjoy the dream and nostalgia of using fine Mauser rifles and cartridges from bygone eras. They are however just fulfilling a dream of a bygone era.

If I were having a double rifle made I would specify a single trigger and be perfectly happy with an inertia set trigger exactly as the same as the superb single trigger and lock on my Miroku. if buying a double I would be only be concerned about fit and performance not what trigger it had.