Although you may rely on expensive optics on your AR-15, it does pay to make sure your iron sights are properly zeroed in just in case you need them. Factories that include iron sights to all rifles and upper halves are bore sighted to 25 yards. Here, you will find out how flip-up and stationary iron sights can be properly zeroed in for maximum accuracy.
The front sight is for elevation while the rear sight will determine windage. In other words, the front sight will control the vertical while the rear sight is in charge of the horizontal. This will help you better understand how to zero in each AR-15 sight so that they work together.
Locating Mechanical Zero
You’ll want to adjust your sights to the mechanical zero, unless you purchased your rifle or upper half from Stag Arms where this step will not be necessary. You will need to rotate the front sight post up or down until you see that the base is flush with the sight. Do the same with the rear sight and you are ready for the next step.
Sights on most AR-15s have a large aperture that is used for shooting close targets. There is usually a line that is present which will help you align the sight using hash marks along the bottom of the rear sight. If you do not find any marks, just rotate the windage knob until the aperture is moved fully to the left or right.
Then, turn it all the way to the opposite direction and count the clicks. By dividing the total number by 2, that is the number of clicks needed to center the rear sight.
Stag Arms Sighting System
Once you have both sights zeroed mechanically, you can then start adjusting for accuracy. Choose a target 25 yards away and fire groups of five shots each. When you find the center of the grouping, you can then measure both vertically and horizontally to properly adjust each sight. Choose either the front or rear sight first and once it is properly zeroed in, then start working on the other. If you are not confident about your grouping, fire another five rounds until you are satisfied.
Since the increments on both sights are set at 1” from the center, this generally means that you can move the sight one click for every inch that the center of the grouping is off. So, if your grouping was two inches off to one side, then two clicks in the proper direction should do the trick. The rear sight should be moved towards the direction you want to go while the front sight should be moved away from that direction.
Confirm by firing another grouping that should put you closer to the target. Remember, it may not be exact, but you can go back and forth until the setting becomes as accurate as possible. Once you have completed zeroing in your iron sights, you’ll be ready to go out and test fire it at longer ranges.