With regards to MS's shooting his .600, I went to my copy of MS's "Death and Double Rifles" and am posting his words for your edification:

Page 102:

"On stationary targets, one must never anticipate recoil or yank on the trigger. Rather one must feel the trigger, almost to the point of being able to feel the sear disengage and the hammer fall. This is called trigger control. If one does not have trigger control, one can never be a good shot. Even with the massice recoil of my .600, I must have trigger control. I must be able to feel the sear disengage. Admittedly, it take practise, but even more, it takes desire to master it."

On page 28-29:

"The buffalo charge in Death on the Run is a good example of what I mean. It is all there for everyone to see. The bull charges at a measured 25 yards away. He is totally committed to killing me. The stage is set. I wait. My .600 Nitro Express double rifle is up and ready, but still I wait. Yes, I could have shot him when he first began his charge, but I did not. I could have banged him when he was lying on the groud, but I did not. Why? BECAUSE IT WOULD HAVE BEEN THE WRONG THING TO DO! When he was about nine feet away, I took the shot. My shot, however, did not kill him. It knocked him to the ground at my feet allowing me time to kill him with the second shot that I held in reserve exactly for that purpose. Though it may appear I was not in control, I was. You can bet on it."