I beg to differ. You can keep both eyes open and probably should as closing one eye increases strain on the muscles of the aiming eye.
Hum , I just pulled out my AR with the iron sights . I have to say at close range and well lit area I can keep both eyes open and see the target . How ever low light or longer ranges its much more difficult .
That was just glancing and or looking down the sights . Im not sure if I could keep both eyes open if I were actually shooting . With the guns recoil and then me having to reaquire the target I think that would be very tuff for me . It is easier with the large aperture then the small one but I guess that goes with out saying .
I will tell you this . The next time im out shooting I will be trying this .
First they came for the communists, and I did not speak out - because I was not a communist , Then they came for the socialists, and I did not speak out - because I was not a socialist , Then they came for the trade unionists, and I did not speak out - because I was not a trade unionist , Then they came for the Jews, and I did not speak out - because I was not a Jew , Then they came for me - and there was no one left to speak out for me.