Open sights work exceptionally well for many shooters. I had a wide V rear and bead front sight on my 9.3x57 using 270gr. Speer at 2,300fps when I shot the moose calf at a lasered 200yards. While that rifle has a scope on it now in my bro's hands, it is not needed for most big game hunting.
The Express sight and bead is an excellent sight for aging eyes as well as young ones.