When it comes to properly zeroing in your AR-15 rifle, there are many schools of thought on the proper way to do it. The AR-15 rifle has two adjustable sights- front and rear. Zeroing elevation adjustments are made using the front sight, and windage adjustments with the rear.
What you need:
- Your gun
- 20-30 rounds of ammo
- A set of binoculars or spotting scope
- Some sand bags to rest the front of the rifle
- A few targets with a clear bullseye
- A range with a 25 yard and 100 yard distance
Step 1 Establishing a Battlesight Zero
The following procedure is that published by the military. It claims to establish a zero at 25 meters, which also sets up a 300 meter battlesight zero. This means that all shots will be within a 9" circle at all ranges up to 300 meters. HOWEVER: Zeroing at 25 meters will not zero the rifle at 300 meters. This can be shown by test firing. There is a growing sentiment in the military to change the zero mark from 25 meters to 42 meters, producing a battlesight zero at 250 meters.
Establish Mechanical Zero -
- Align the windage indicator mark on the 0-2 aperture with the center line of the windage scale (the unmarked aperture is up)
- Rotate the elevation knob down until the range scale 8/3 (300-meter) mark is aligned with the mark on the left side of the receiver.
- Rotate the front sight post up or down as required until the base of the front sight post is flush with the top of the sight post well.
Carefully aim and fire each shot of a 3-shot group at a paper target set up at 25 (or 42) meters. If your shots are not striking the point-of-aim, then adjust your sights.
- To raise the shot group, rotate the front sight post in the direction marked UP (clockwise)
- To lower the shot group, rotate the front sight post in the direction marked DOWN (counter-clockwise)
- To move the shot group left, turn windage knob counterclockwise
- To move the shot group right, turn the windage knob clockwise
Repeat the fire and adjust sequence until you find that you have tight groups around your point of aim.
When you have successfully completed these procedures, your rifle will be combat-zeroed. Once zeroed, all other range markings on the elevation knob will likewise be zeroed.