The NEMO chambered in 458Win Mag IMO is simply a show piece. A "let's see if we can ............" piece. It has NO practical usage. In Africa only bolt and doubles are used. Why ........?....... reliability. The doubles are even more sought after by the guides if they can afford one. Why ?? Reliability.
In the bolt guns seems that most that are used are the controlled round feed. Again ... reliability. When you have a charging (insert name here)that is not the time to have a mis-guided round. Hence the double. The guides would rather give up a round or two and have a completely reliable gun.
And ..... just how fast can they reload ?? I saw a demo one time of a African "white hunter" reloading a double (577NE,IIRC)and it was unbelievably fast. Seemed like about the time it would take you to unshoulder a bolt gun and work the action.
The ammo in the pic is: R-->L --- 223Rem,458Win Mag(400gr Sierra),460Wby Mag(510gr Hornady),and ....... a round from my yote gun. --- SAWMAN