Grandveneur….I for one appreciate hearing of your experience with these cartridges, sorry that you are feeling the need to depart.

Two thoughts here:
1) I have an original Mauser Type A in 10.75x68 that weighs 7lbs 8oz (no scope) and has a horn buttplate. The rifle is quite lively enough with the original 347 grain bullet hand loaded to ~2150'/sec. I would not be interested in trying to duplicate a .404 Jeffery 400 grain bullet load at that same velocity. I would have to guess that the non professional hunters in the old days would agree…….
I think some people just like to BS about what amounts to a moot point. The 10.75x68 could be loaded to equal an original .404 Jeffery ~2100'/sec with modern powders and pressures that were not considered in the old days, but why do it?

2) As to hunting effectiveness, there were guys like John Taylor that trashed the caliber and where his writings were popular it resulted in a dismissal of the cartridge as inadequate for Africa.
On the other hand there are Tony Sanchez Ariño and Pierre van der Walt that say it was & is (with the proper bullets of course) quite an adequate cartridge choice for most African game.
It must be noted that the German ammunition is said to have used bullets that could not stand up, while the results with Kynoch ammunition were said to be quite adequate.
Given the relative popularity of the Mauser and the 10.75x68, it seemed to fill the need for a rifle that would put meat on the table and suffice for dealing with the bulk of sport hunting in Africa. Optimum for the Big 5? Maybe not so much, but I am led to believe that most of the colonist farmers did not engage in that activity anyway.
So just my 2¢
- Mike