How to Zero an AR-15 at 100 Yards
Woody's answers are based on published federal and state law. Not legal advice. Consult a licensed attorney for your specific situation.
Set up at 100 yards, fire a 3-shot group, measure deviation from point of aim, then adjust windage and elevation turrets accordingly. Each click typically moves impact 1/4 MOA at 100 yards.
How This Affects Your Build
A proper 100-yard zero is fundamental for precision shooting with the AR-15 platform. Most serious shooters use this distance because it provides a true baseline for understanding your rifle's ballistic performance. The 100-yard zero eliminates guesswork when making longer shots and gives you confidence in your equipment's capabilities.
The Detail
Start with a stable shooting position using sandbags, a bipod, or a shooting rest. Your rifle should be completely motionless between shots. Fire a careful 3-shot group aiming at the same point of impact, then measure the center of that group relative to your point of aim. Don't chase individual flyers or adjust after every single shot.
Most AR-15 rear sights and optics use 1/4 MOA adjustments, meaning each click moves your point of impact roughly 1/4 inch at 100 yards. If your group is printing 2 inches low and 1 inch right, you need 8 clicks up and 4 clicks left. Make your adjustments, then fire another 3-shot group to verify the correction.
The process typically takes several iterations to get dialed in perfectly. Environmental factors like wind, temperature, and ammunition consistency all affect your results. Use quality ammunition from the same lot number for your entire zeroing session. Cheap or mixed ammunition will give you erratic groups that make it impossible to establish a true zero.
Once zeroed at 100 yards, you can calculate holds or dial adjustments for other distances based on your ammunition's ballistic coefficient. A 100-yard zero typically puts you about 2.5 inches high at 200 yards and back on target around 250-300 yards, depending on your load and barrel length.
Build Impact
Your barrel length, twist rate, and chosen optic all influence how your rifle will perform at 100 yards. A quality barrel with a consistent crown is essential for achieving repeatable accuracy during the zeroing process.