You're absolutely correct if someone is using both.
If the optical sight is working, you ignore the BU sights.
And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.
I was making a statement. there is people that co-witness while their optics are working fine. I find it weird that people would use both the red dot and irons at the same time. The reason i mentioned that was because I was under the impression that the op had a rifle with the triangular fixed front sight post
Guess I'm weird like many others. After you cowitness the rear BUIS does fold down out of your field of vision while the fixed front isn't a problem for me, in fact I like it there since it doesn't slow me down.
Also, if you bottom third cowitness you don't have to look through the rear aperture even if it's up.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek