How To Zero A Red Dot On An AR15

In this quick guide let's go over how to zero AR15 when using a scope, a red dot or a pair of iron sights. While different ammo weight and barrel length will yield different shot group results as distance increases. In the context of this guide, will only focus on using 55 grain 5.56 ammo with 16" barrel.

The zeroing techniques behind each aiming solution are similar. The shooter will pick a shooting distance and zero the rifle and memorize the hold over for future references. 

Zeroing Procedure

  1. Properly mount optics to prevent necessary error that can be avoided in the first place
  2. Pick a zero distance (Distance is roughly the muzzle to the target)
  3. Use a laser range finder to estimate the distance
  4. Send at least 3 shots slow and steady
  5. Measure the shot group distance
  6. Make appropriate adjustments
  7. Re-confirm zero

Determine Zeroing Distance

Here are the most popular AR15 zeroing distances

Please note that optic mount height can affect the shot group as distance increases.

The military standard is a 25-meter target, which gives you a zero for 300 meters (In the perfect world). But many shooters prefer a 50-meter target, which gives you a tight shot group zero around 200 meters.

Understanding The 5.56 NATO Ballistic Performance

The term "effective" defined by the US Army is the maximum range a projectile is expected to inflict casualties or damage 5.56mm NATO projectile is about 200 to 250 meters (218-273 yards). This is because half of the firefights occur well beyond 300 meters, making the weapons marginally effective.

556 nato muzzle velocity
556 ballistic drop performance

The 5.56 bullet's effective range is less than its advertised range. The 5.56mm NATO round may reach a target at 460 meters, but it may not have the desired impact or lethality at that range.

Setting Up Your Rifle: The Basics

Zeroing AR15 Iron Sight

Use the small sight aperture: On the rear side of your AR-15, make sure you're using the small sight aperture. This is crucial for accurate shooting for shooters with poor eye sight.

Lower the rear sight: Lower the rear sight as far as it will go. This is your starting point.

Adjust for distance: If you're zeroing for 300 meters and you have an older AR-15 model (like an A1 or A2), move the rear sight one click past the 300 mark.

This gives you a one-minute angle up. If you have a newer model with a removable carrying handle and two knobs on the side (like an 83 or 84), you'll need to move up two clicks. These models have finer thread adjustments, which are half-minute of angle clicks.

For windage (left-right) adjustments, use the knob on the rear sight. For elevation (up-down) adjustments, use the front sight. Remember, clockwise turns raise the point of impact, while counterclockwise turns lower it.

Stabilize The Rifle

Stabilize your rifle: Make sure your rifle is stable. The best way is to place it on a sturdy tripod (If not going prone) You don't want it move around when you're shooting. Sandbags or a rubber block can also provide excellent support.

Hold your rifle correctly: Many shooters prefer to support the rifle with their hand under the forearm. But we recommend a "sniper hold". This allows you to make more stable movements and adjustments by raising and lowering your support hand.

Check your sight alignment: This is crucial. The front sight needs to be directly in the middle of the rear sight aperture. If your sights aren't perfectly aligned, your sight picture will change every time you move your head, resulting in larger groups downrange.

Zeroing Optics

Whether you are using a red dot sight, a prism scope or a rifle scope. The turret adjustment value is something the shooter must take note of. Based on this value, the shooter can calculate the exact number of clicks to dial to zero the optic.

zeroing-red-dot-100-yard.png

Here is the simple math to follow:

adjust-MOA.png

Take how much you have missed (In inches) from the point of aim divided by the zeroing distance (yard) in the 100th. Then divide that value by the click adjustment value (MOA). This will give you the number of clicks to dial.

Don't be afraid if the number you have calculated looked like you have to dial like 50 or 80 clicks if you are zeroing for 25 yards. This is totally normal. As the target range gets closer, more clicks are needed to bring that point of impact closer to the point of aim.

zeroing eotech

Remember, most turret adjustment direction reference the point of impact, NOT the point of aim. And the easiest way to remember which way to dial is the following:

  • If the shot group is 4 inches off to the left of point of aim, then it's about moving 4 inches to the right. So dial 4 inches to the right.
  • If the shot group is 4 inches above the point of aim, then it's about moving the elevation turret 4 inches down. So dial 4 inches down.
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