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MOA Explained

80 Percent Arms   |   Aug 26th 2021

MOA is an acronym that stands for “minute of angle.” A minute of angle is an angular unit of measurement. One MOA is equal to 1/60th of a degree. We use MOA to determine firearm accuracy by measuring the size of a grouping, or several shots, on a paper target that will often have the ruler guides like in the photo above. Each box is 1 square inch and is therefore 1MOA.

At 100 yards’ distance, a 1 MOA grouping spreads out across one inch. However, 1 MOA is a different size of grouping depending on the target’s distance. For example, if you were to shoot a grouping of bullets at a target 500 yards away and all your shots hit within a 5” group that would still be considered 1MOA.

Utilizing MOA is also helpful in zeroing or sighting in optics such as red dot sights, holographic sights, or low power variable optic scopes. Knowing where you hit on a paper target in relation to where you specifically want to hit it informs the shooter on how to properly adjust to zero in their optic and helps improve the user’s accuracy.

MOA Breakdown

If none of that helps you, then just understand this basic idea: (the figure above should help, but might be over complicated) when it comes to shooting, there are two lines you need think of and that’s your line of sight which is also known as your point of aim; then there’s the flight path of your bullet which can also be referred to as the point of impact. Where you aim, may not necessarily be where your projectile lands. That’s why we have to zero our optics and even some iron sights.

The relation between our line of sight and the flight path of the bullet is dependent on a few factors but primarily it relies on the distance between you and the target. After that, you’ll be able to factor in additional data points to help inform you on where you should be aiming, what your sight alignment you should be using (if using a handgun), or how you should be utilizing your reticle like if there needs to be any holdover, as an example.

Minute of Angle then comes into play as we know how to consider all the aforementioned and unmentioned factors that go into shooting accurately and essentially we use MOA as not only a sighting tool but also unit of measurement which in layman’s terms can quickly define how accurately a gun can shoot up to an ‘X’ amount of distance.

What is MOA? How do we calculate for it?

Calculating for MOA — Let’s say you are trying to determine what 1 MOA is at a variety of distances. Well, it’s quite easy. All you have to do is use this simple formula: Divide your target’s distance by 100 and that is your answer. So if your target is 300 yards out - divide that number by 100 and it equals 3. 1MOA at 300 yards would be 3 square inches.

Importance of Understanding MOA Formula

Well, if you’re doing long distance shooting, your scope adjustments can be quite large. If you’re shooting at a target 500 yards away, we know the 1MOA is 5”. However, if we need to adjust either the elevation or the windage turrets by 3 MOA, that would be a total of 15 inches in difference. Even if you don’t need to adjust your scope, perhaps you just want to adjust your aim on the fly. Understanding this will help you accurately hit targets that are perhaps further than you are used to. Reticles can also help a lot.

Using MOA to Zero Your Sight

This is true for both red dot sight and long range scopes — when zeroing or ‘sighting in’ your optic, don’t think in “clicks” when making adjustments. You have to remember to check what the rate of MOA per click your optic has before adjusting. Most optics are ¼ MOA per click adjustments. So what does that mean? Say you need to move your reticle 3 MOA in a certain direction. In order to do that, you’ll have to do some basic math because 1 MOA in this case would equal 4 clicks which comes out to a total of 12 clicks total to make that adjustment.

Mil vs MOA vs MRAD

When people compare MOA versus MRAD or MIL they’re referring to different scope measurements. See the photo above for a scope with a MOA reticle vs a MRAD reticle. MRAD and Mil or “MIL-Dot” are actually one and the same. MRAD specifically stands for mill radians or is called “MIL” for short. “Mil-dot” is the abbreviated form of milliradian and dot. Earlier we showed you how at 100 yards 1MOA is equal to 1” right? At the same distance 1MIL is equal to 3.6”.

What’s a Radian?

A milliradian is 1/1000th of a radian. So what’s a radian? A radian is the measure of distance traveled around a circle. Depending on who you ask, there are (US Army standard) 6,400 milliradians in any given circle.

What is a DOPE card?

D.O.P.E. stands for data on previous engagements. It’s a collection of ballistic data that can be very useful when engaging targets at far off distances in a wide variety of situations. These situations might account for distance of target, the speed of the wind, the temperature that day or even the humidity in the air. In slightly simpler terms, a DOPE card/sheet/book is to help you adjust your aim to calculate for bullet drops and or wind drift. The more data you have recorded, the better understanding you’ll have of your rifle’s “dope” and will eventually be able to shoot accurately in more situations. Think of it like a cheat sheet but for rifle accuracy.

What Is Barrel Twist Rate?

When we talk about barrel twist rate it refers to the ratio of inches that a bullet needs to travel down the barrel in order to make it spin in one full turn. So let’s say your barrel has a 1/7 twist rate. That means once fired, a projectile will need to go 7 inches down the barrel in order to make one full turn.

Is a higher barrel twist better?

If you’ve ever heard the phrase “bigger is not always better” that is partially true in this case. That’s because the lower the twist rate is, that means the faster your projectile will spin. Now, unless you’re doing extremely long distance and precision shooting your twist rate will not have an affect on your bullet’s accuracy or velocity. However, it’s all semantics really as your optimal barrel twist rate is going to depend on what caliber you are shooting, what kind of load you’re using, and the length of your barrel. 

If you’re using a larger .30 caliber bullet like .308 then yes, definitely. You’re going to need a slower twist rate and or a longer barrel to be able to better stabilize that longer and heavier bullet prior to its flight to your intended target. If it’s a smaller caliber like .223 Remington, then a lower twist rate like 1/7 or 1/8 is what you should be using.

What is the most accurate barrel twist?

Again, it depends on what caliber you’re using, the load and your barrel length. But overall and objectively speaking the 1/8 twist rate is the best twist rate for stabilizing just about any load for 5.56mm being shot out of a semi-automatic AR-15. Most higher performing match shooters you see will be using barrels with 1/8 twist rate in their rifles.

In the 2010s, most companies were using 1/9 twist rate barrels but soon afterwards the mil-spec standard became 1/7 twist rate and that’s simply what the industry has moved towards as a whole. That being said, we carry barrels in our AR15 build kits in both twist rates. 

Start your next build with 80% Arms!

Now that you understand MOA better, get started on your next 80% AR build so you can slap on an LPVO and practice those angle measurement skills you just learned. Already have a build? Don’t forget an optic! Whether you’re using a Holosun Red Dot Sight or a Trijicon MRO, the knowledge in using both optics regarding minutes of angle is exactly the same.