I've got the 4 mil on a 22/45, and it's a great little sight. I agree, the battery compartment is a little awkward, but it's a definite improvement over the FF II where the battery was located underneath the unit and the whole sight had to be removed. And in reality, how often are you going to need access to the battery? The brightness settings take a little getting used to as well. They have to be cycled completely through each time you use the unit. First push of the button is auto adjust brightness, then high, medium, low and off with each subsequent push. If your looking for a sight that's super compact, lightweight and solidly built you won't go wrong with the FF III. Just remember your mounting differences between an AR and shotgun. That little sight will probably be way too low just mounting it directly to the picatinny rail on your AR. You'll most likely need some sort of riser mount, which Burris offers.