How to adjust a red dot sight

Red dot sights are the most popular type of optic for firearm owners. They provide a clear, wide sight picture and they don't suffer from parallax error (that means your head and eye placement doesn't matter). But to squeeze that accuracy out of your new red dot, you need to zero it so your point of aim matches your point of impact. Here's how.

How Red Dot Reticles Adjust

Only ever use iron sights and conventional rifle scopes? You'll be happy to know red dots adjust exactly like any other sight: You make adjustments to reticle placement, based on a known distance to your target, using windage and elevation turrets or buttons built into the red dot itself, like how the Bushnell TRS-25 (shown up above) has adjustment turrets like the Trijicon ACOG rifle scope next to it.

Whether you're using a reflex, prism, or holographic red dot, their differences don't matter when it comes to zeroing. Without getting technical, all red dot reticles adjust so that point of aim matches point of impact typically with quarter, half, or 1-MOA clicks, like most other optics.

Understanding MOA

"Why do I need to know this?" Because your red dot's instructions probably indicate that your reticle adjusts using MOA. If you're zeroing your firearm with your new red dot, you need to be able to convert the difference between point of aim and point of impact from inches to MOA.

If you're not sure what MOA is, exactly, we're going to keep it simple: 1 MOA measures 1 inch at 100 yards. That means 0.5 MOA is 0.5" at 100 yards, and a 0.25 MOA is 0.25" at 100 yards. As distance decreases, so too does the conversion from MOA to inches. At 25 yards, 1 MOA is 0.25", 0.5 MOA is 0.25", and 0.25 MOA is 0.0625".

Want to fully understand MOA? Read the full guide here.

You don't need to understand the technical stuff when it comes to MOA. You only need to know how to convert inches to MOA in order to effectively zero your red dot - and to make adjustments downrange at different wind speeds and distances.

1. Convert inches to MOA.

Let's use examples. You're zeroing a handgun with that sexy new Sig Romeo 1 red dot. You're firing at a target 25 yards away. You're aiming for the bulls-eye and your round lands 5 inches below the center. How do we turn 5 inches into MOA so we can adjust our optic? With this formula:

[Distance between aim and impact in inches] divided by [distance to yard / 100] = MOA.

Let's plug in 5" as our difference between aim and impact, and use 25 yards as our distance:

5 / [25/100] = ?

5 / 0.25 = 20 MOA low.

Let's say you're zeroing with a rifle at 100 yards and your round lands 5" low once again:

5 / [100/100] = ?

5 / 1 = 5 MOA low.

Using this formula, you're converting the inches you need to correct your aim into MOA, so you can adjust. But how do you make those adjustments?

2. Adjust your red dot's reticle.

The amount of MOA your red dot's reticle moves per adjustment click, in addition to the total number of MOA you need to adjust, determines how many clicks you need to make to adjust your point of impact. 

Using example #1, we determined we need to adjust our handgun red dot's reticle 20 MOA upward. On a red dot with 1-MOA turrets or buttons, you'd simply adjust 20 clicks or button presses upward. If each click or turn corrects by 0.5 MOA, it'd be double, or 40 clicks. And if it's 1/4-MOA (which is common), it'd be quadruple, or 80 clicks.

Using example #2, we'd make 5 clicks upward with 1-MOA adjustments, 10 clicks upward with 0.5-MOA adjustments, and 20 clicks upward with 1/4-MOA adjustments.

"Which direction do I adjust my turrets?"

Always click your reticle's adjustment turrets or buttons in the direction you want to shift your point of impact. That means if you're aiming low, you should move the up/down (elevation) adjustment up. If your rounds are landing left of the target, you'd move your left/right (windage) adjustment to the right.

How to Save Ammo Zeroing

Now you know how to convert inches to MOA, and you know how to input your adjustments into your reticle to zero it. But how do you make zeroing easy? You might install your red dot and find that, even at 25 yards, your un-zeroed reticle  is so far off that you miss completely. This is a more common problem than you think. And you need a way to easily measure the difference, in inches, between your aim and impact on the target itself.

Get a laser boresight.

This writer spent eight years in the military, sending thousands of rounds to targets at the qualification and zero ranges. I am here to tell you, having ran ranges and having helped hundreds of soldiers zero their rifles, that you absolutely need a laser boresight. Missing the target and trying to guess how far you're off - and then making big, blind adjustments to try and get on paper - will waste time, targets, and money.

So, why is the boresight so important? A decent laser boresight costs about as much as a couple rounds of loose ammo, and it'll save you boxes of ammo. Using the boresight, you'll get an easy-to-read estimation of where a live round will land on your target relative to your point of aim. You can then easily adjust your reticle and get familiar with your adjustment knobs or buttons, without ever having to pull the trigger. A boresight can get you to an almost-perfect zero within 50 yards, requiring only minor adjustments, and you can probably achieve a full zero at 25 yards.

Use a zeroing / tighting target.

Even if your boresight gets you your aim damn close to impact, you should always confirm your zero at a known distance. And chances are, you'll want to send rounds on target to confirm your accuracy either way. To make zeroing at the range with live ammo easy, you should grab some Sighting Targets. 

These targets come printed with perfect 1" squares, making MOA adjustments at known distances - like 25, 50, or 100 yards - super easy. You don't even need a spotter scope. Just count the blocks between your point of impact and the center of the target to measure your difference in inches.

FAQ

Q: Can I zero other optics with these instructions?

A: Yes. Red dot scopes, iron sights, and variable or fixed-power rifle scopes, all adjust using the same basic principle: Adjustment point of aim in order to shift point of impact, using windage and elevation adjustments.

Variable-power scopes require a bit more consideration when zeroing. Read our in-depth guide on how to zero a scope here.

Q: How can I calculate the number of clicks I need to adjust my reticle?

A: Multiply the observed difference between your points of aim and impact in MOA. Multiply that number by the MOA per click listed on your buttons or turrets. If it's not listed, check the manual for your optic. Example: If you observe a 20 MOA adjustment is required and your turrets say "half an MOA" or "0.5 MOA" per click, multiply 20 by 0.5. This would be 40 clicks.

Q: What if my red dot uses MILs instead of MOA?

A: MILs are the metric system's equivalent of MOA. One MIL equals 1 centimeter at 100 meters, whereas one MOA equals 1 inch at 100 yards. If your red dot uses MILs, then simply measure your difference between aim and impact in centimeters instead of inches. Zero at a known distance of meters instead of yards, and determine how many mils per click your reticle requires to make adjustments.

DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At RangeOften.com, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.

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