The iron sights on the top of the ACOG are crap. Most of the guys I know who use the ACOG (myself included) either have taught themselves to aquire the sight very qucikly throught the scope or they use what is called Jpoint which is simply a red dot sight that sits where the iron sight would go (it actually screws into the same holes). This is what I use and I really like it. It takes some getting used to at first because it sits higher but you can actually aquire the picture quicker. I just put a 10 meter zero on the Jpoint and get my hold off out to 25 meters and beyond that I have the ACOG. It is a pretty good system.

SFC W