In all the observations about bullet softness and ability to penetrate or lack of it, nobody has cottoned on to the fact, or at least mentioned it, that in all calibres the long heavy bullet provides stability and penetration rather than a short for calibre lighter bullet. This is the very reason why the smaller 7x57 nd 6.5x54 cartridges proved quite capable of racking up good dangerous game kills in the hands of a shooter who could place the bullets to do the damage. Bell being perhaps the most famous but other hunters of his era in Africa also using these calibres for big but less dangerous game. The 9.3 and 375 cartridges also built their reputation on the long heavy bullets they used. All these cartridges operated at moderate velocities.
Taking a 350gr .423" bullet, no matter how strongly constructed or how fast it is driven, is not the key to a reliable and consistent big game killer.

There is a reason why the 375H&H, 404 Jeffery, 416 Rigby and 425 Westley Richards earned such magnificent reputations, and for the first two such common and widespread use, as large dangerous game killers in Africa. It was the long heavy bullets, irrespective of construction and velocity, that all these cartridges had in common that made their reputation, not short stubby varieties.