Maybe It is an optical illusion, but I agree that it would have to be tilted higher. I have hit a buffalo target at 1000 yds with iron sights with my .500 Linebaugh Long 2 out of 5 tries. With the reflex sight he is using it would have to be shimmed quite a bit at the rear.

I used a sight picture on my gun that allowed me to just barely see my barrel in the rear sight notch and placed the front sight on the target.

BTW the gun I used is the one in my avatar.