That's the whole point of the red-dot; all you have to do is put the dot on the target - it doesn't matter where the dot appears to you in the lens and the dot doesn't have to be lined up with anything on the gun. That's what makes them faster than irons for CQB. Take the thing to the range and shoot it to prove it to yourself. 'Co-witness' has no tactical meaning. All it means is that if you sight on a target with the BUIS (sighted in at the same range you sighted in the red-dot) then actually turn on the red-dot, the dot should be sitting right on top of your front sight post, which is a neat effect with no meaning whatever. You don't use the BUIS and the red-dot at the same time. The purpose of the BUIS is so you can continue to fight if the red-dot fails. As long as the lens is not damaged, you continue to sight through it. If the lens is damaged, that's where the quick-release mount comes in handy; drop the red-dot and keep shooting.