I actually just got back from sighting mine in. I've had the M3 for a few months and finally just got out to try it. Sadly my gun slid off the wall I had it resting against and the knob to adjust the dot size broke off. I was able to drill a hole into the remaining knob shaft and glue a thumb screw from a computer into it. It isn't a fix that will hold up but at least I was finally able to try the sight. uuggghh! Guess I'm going to have to buy another.....