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How to Sight In a Red Dot Scope On Your AR-15 [Easy]

L.p. Brezny | Updated February 26, 2024 | Why You Should Trust Us | How We Earn Money
Cover photo of how to sight in a red dot scope showing the target view through a red dot scope

Red dot scopes are a must-have for hunters, shooters, or tactical professionals who like to shoot short to mid-range. They optimize your shooting experience, but if you don’t sight them in properly, all you’ll be getting is inaccurate shots. 

In this article, I’ll be explaining how to sight in a red dot scope on your AR-15 the easy way.

For similar reading see our guide to the different high quality red dot sights on the market.

Key Takeaways

  • Learning how to sight in your red dot scope will increase your accuracy in the field.
  • If you don’t want to sight in your red dot scope with ammunition, you can use a boresighter, which is also an effective method.
  • When mounting your red dot sight, place it as far forward as possible to maximize peripheral vision and balance the AR-15’s weight.

How to Sight in a Red Dot Scope

When sighting your red dot scope, place your target at the desired zeroing-in distance. Mark your bullseye, which will be your point of aim (POA), and then fire several shots at the target.

Image of a man aiming at the target from afar

Most likely, you won’t hit the target. Where your bullets hit is what we call the point of impact (POI). Measure the difference between the POI and POA in inches and convert them to Minutes of Angle (MOA). Don’t worry – I’ll explain what MOA is in just a bit.

Adjust the windage (left and right) and elevation (up and down) knobs, then shoot at the target again to confirm your sighting is accurate.

Understanding MOA

Sighting in has to be done correctly if you want the rounds to hit the target. That means making the right adjustments to the elevation and windage knobs. These adjustments are measured in Minutes of Angle (MOA).

Image of the adjustment knob of a red dot scope

If you check your red dot sights, you’ll notice that the reticle adjusts using MOA. And when you’re trying to sight in your red scope accurately, you must convert the difference between POI and POA to MOA.

So, what is MOA, and how does it work? 

Well, the adjustment value on red dot scopes used on rifles is usually 1/2 MOA. That means each click shifts your POI to half an inch at 100 yards. Still, be sure to read your red dot scope’s manual to confirm the adjustment value, as it may vary across brands.

With that information, start shooting at your target. Three rounds are a good point of reference. 

Move to the target and observe how far the POI is from the POA. Let’s assume your rounds hit two inches above and two inches to the right of the POA. You need to adjust your elevation up, four clicks, and your windage, left four clicks because one click equals half an inch.

Understandably, your red dot sight might be using MILs instead of MOA. But don’t worry, as the math is still the same. 

While 1 MOA equals one inch at 100 yards, one MILs equals one centimeter at 100 meters. Therefore, measure the difference between POA and POI in centimeters rather than inches.

Image showing 1 MOA click on a turret cap

Also, your zeroing distance will have to be in meters instead of yards. This will help you determine how many clicks you must make when adjusting the turrets.

Check out this video if you want a visual guide on how to sight in a red dot scope:

Red Dot Zero Distance

When sighting in your red dot sight, you must choose the appropriate distance. If you’re using a rifle, the recommended distance is 50 yards. Sometimes it’s referred to as 50/200 yard zero. 

That’s because when zeroing in your sight at 50 yards, the POA and POI are the same as at 200 yards. 

Well, they aren’t exactly the same, but they are very close.

Zeroing a red dot scope at 200 yards is way too far. It will be hard to see your target well and shoot small groups. Zeroing in at 50 yards is more practical and doable, which is why I’d suggest this distance.

Image of a man aiming at a white target

Another reason shooters recommend 50 yards is that even a new shooter can accurately shoot that distance with a red dot scope, making it easy to achieve tight groups.

At a 50-yard range, each click is equivalent to 1/4 an inch. If we use the earlier example of two inches, then you have to adjust the elevation and windage turrets by eight clicks to ensure the POA and POI are aligned.

Sighting in Red Dot at 25 Yards

Let’s assume you decide to sight in your red dot scope at 25 yards. This is also a common distance to work with. 

At 25 yards, a click is 1/8 an inch. If you sight in your red dot scope at 25 yards and after the first shot, the POI is 2 inches to the left and 2 inches below your POA, it means you have to adjust the knobs by 16 clicks right and 16 clicks up for the POI and POA to align.

Zero Red Dot at 10 Yards

If you often use your rifle for self-defense, you will want to zero in your red dot at 10 yards. That way, you can be confident your weapons will be ready if such a situation arises, as most self-defense situations occur within that distance.

Image of a man holding a rifle with a red dot scope

When shooting at 10 yards, one MOA is around 1/20 of an inch. Remember that a red dot sight’s adjustment value is 1/2 inch at 100 yards. 

So, if you shoot and the difference between our POA and POI is two inches to the left and two inches up, you need to adjust your turrets by 40 clicks.

How to Zero a Red Dot Without Shooting

Ok, let’s get away from the calculations and technicalities. You can zero in your red dot without shooting. Here’s how to do that:

Use a Boresighter

One of the easiest ways to sight in a red dot scope is by using a laser boresight. If you want to save your ammo, this is a great method. 

Image of a boresighter inserted into the muzzle of a rifle

The device can come in two forms. The first one resembles the shape of your rifle’s caliber so that it can fit in the rifle chamber. The other one comes with a stem that you insert into the rifle’s muzzle.

So, how do these work? 

Turn it on and carefully place it either in the rifle chamber or at the end of the barrel, depending on what type of boresighter you have. After, point it at your target. It will direct a laser dot at the target. 

When you point your rifle at the target and look through your scope, you’ll notice the difference between where your red dot is pointing and where the laser sight points. Adjust your elevation and windage knobs so that the red dot is lined up with the laser.

Image showing a laser sight pointed at the target

If you do this correctly, you should have successfully managed to sight in your red scope without firing a single shot. When you’re ready to shoot, don’t forget to first remove the boresighter.

Manual Boresighting

If you haven’t bought a boresighter, you can do this manually. The process below is for manual boresighting an AR-15.

So, you first separate the upper and lower receiver and remove the charging handle. Place your weapon on a steady platform and look down through the bore to the bullseye.

Next, move to your red dot scope and adjust the dot to align with the bullseye. Now take another look through the bore to ensure it didn’t move when you were adjusting your scope. If everything looks great, you can reassemble the rifle.

Sight vs Scopes

We’ve all heard people using the terms red dot sights and red dot scopes interchangeably in a sentence. In fact, we might have done the same thing. 

Red dot sights aren’t scope per se. By definition, scopes have a magnification power that can be 4x, 8x, and so on.

Image of a red dot sight

Red dot sights aren’t scopes because they don’t make objects appear bigger. On the other hand, people use scopes to make it easy to hit their target over varying distances. 

Sights, red dot sight included, don’t magnify anything. We use them to predict where a bullet will hit when we shoot. That said, red dot sights can be paired with magnifiers to make the target appear bigger.

These sights are usually used for short distances. But when you combine them with a magnifier, you can hit targets as far as 200 yards, which is impossible when using red dot sights only.

Mounting Red Dot Sight

While you may know how to sight in your red dot scope, if you don’t know how to mount it properly, your shooting experience will likely suffer. 

When mounting, be sure to place it as far forward as you can. The major reason why is to have as much peripheral vision as possible.

If you place the red dot sight far back, it will obstruct your peripheral vision. To prevent that, install it far forward to maximize your vision and reduce tunnel vision. 

Aside from that, placing it forward gives your AR-15 balance by distributing weight evenly on your weapon. That said, here are a few tips for mounting your red dot sight.

Apply a Threadlocker

Firing rounds cause vibrations to run through your gun, which can loosen screws and cause your red dot sight to slide out of position. When you have spent several minutes trying to sight in your optic, the last thing you want is to lose your zero.

Image of a hand holding a blue threadlocker and different types of threadlocker in the background

Luckily, there’s a simple solution, which is applying a threadlocker on the screws when you mount your sight. It’ll hold your optics in place. 

Blue Loctite is a good option because it keeps the screws in place but still allows you to remove the optics easily when you want to.

Avoid red Loctite though, as it will permanently lock the screws in place. Remember, we want to be able to uninstall our sight in the future to clean and maintain the rifle.

Push Your Red Dot Forward When Screwing It

There’s always a tiny space between the mounting holes and the screws, which can make the red dot sight move around. So, push the optic forward while tightening the screws to ensure it fits snugly and doesn’t have room for much movement.

For more on red dots see our guide to the Trijicon optics RMR footprint and what sights work with it.

Frequently Asked Questions

Can you zero a red dot with iron sights?

You can zero a red dot with iron sight, although it’s not exactly the most accurate method. Ensure that you have aligned the iron sight’s POI with the red dot POI.

Do you use front sight with red dot?

You don’t use a front sight with a red dot because the aiming concept of red dots doesn’t involve using front sights.

What distance should you sight in a red dot rifle?

The distance you should sight in a red dot rifle is 50 yards. However, if you mainly use your weapon for home defense, sight in at 25 yards.

Do you sight in a red dot scope?

You do need to sight in a red dot scope. Like other types of scopes, you have to sight it in to increase your accuracy.

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