I am no stranger to peep sights using them for Service Rifle and Palma High Power Rifle matches. Up until about 7 years ago I had only killed 2 big game animals [except for game shot with a pistol] with iron sights. I started using the express sights on my doubles. It took a few succussful shots with the iron sights for me to have the same confidence in them that I had in a scope. I got to where I enjoyed iron sight hunting so much I had to "force" myself to use the scope on my 9,3x74R to gain conficence with it. I much prefer the Express type sights on my doubles to peep/ghost ring sights. I have used them enough that I have confidense in them. In fact on my June Africa trip I can distinctly remember the sight picture on every animal I shot with the scope and the 9,3. With the 450 No2 I do not even remember even looking at the sights

. I know I did [look at them

]because I never had a miss with the 450 No2. I guess because I have shot that rifle so much it has become second nature, but I do not remember "aiming" at the 2 buff or 3 elephant that I shot. This is also true for the caribou, black bear shot with the 450/400 and the black bear I shot with iron sights and the 9,3 Chapuis.
I just do not remember consciously "aiming" I just shoulder the rifle and pull the trigger. With a scope I always remember "aiming". Strange but true. I guess the secret might be to shoot your iron sighted rifles a lot, until they become an extension of your will. [Use the Force

]
I do not know how else to explain it.