Minute of Angle Guide

Spend any amount of time looking at rifles, scopes or scope rings like AR 15 scope rings, and you’re going to see a strange acronym pop up: “MOA”. Those three letters stand for Minute of Angle. Strangely enough, that tells us absolutely nothing about what that actually means.

While it’s called “minute of angle” in the firearms world, the official/scientific term is minute of arc. As you may remember from school, a circle has 360 degrees and a minute of arc is equal to 1/60 of a degree or 1/21,600 of a circle.

Ok, so thanks to some mathemagical equations that I don’t want to bore you with (I learned my lesson on that one), in the firearms world 1 MOA translates to about 1 inch at a distance of 100 yards. So when a rifle has the words “1 MOA Guarantee” written prominently on its box and advertising material, what they’re saying is that, out of the box, it is accurate to 1 inch at…what? That’s right: 100 yards. That ratio is important to keep in mind if you want to shoot rifles: 1 MOA = 1” @ 100 yards. Memorize that information. Trust me.

Right, so how is this useful to you? Well, those little knobs on scopes aren’t just for making it look interesting, they’re for adjusting where the lines inside the scope cross. Side note: This next part may sound a bit obvious but we like to take a “how to boil water” approach to things. I’d rather not just assume everyone knows a certain bit of information.

The crosshairs of a scope don’t come ready to go. Just putting it on a rifle doesn’t mean that you can go out and punch 1 MOA groups right away. A new scope has to be sighted in. This means that is must be set up so that the crosshairs line up with the actual bullet impact spot. Ninety percent of the time, this is done at 100 yards (see a pattern here?). So one knob moves the crosshairs up and down while the other knob moves them left and right. Typically, those knobs are incremented to known distances. You’ll actually be able to feel them click to the next increment. Depending on the scope manufacturer and quality, those increments can be anywhere from ½ MOA all the way down to ⅛ MOA for each click.

Let’s say that you’ve boresighted your rifle to get an approximate starting point. What’s boresighting? We’ll talk about that in another guide but for now it’s just making sure that the crosshairs line up with where the barrel is pointing. That’s not always where the bullet will impact, mind you. It’s just a starting point.

So you take a few shots with the crosshairs lined up in the dead center of the target. You take 3 shots and then take a look at where they hit. For this example, let’s say that the bullet is impacting about 3 inches down and 2 inches to the right. Knowing that your scope has, say, ¼ MOA increments, you can quickly dial in how many clicks you need to adjust in order to bring that group closer to your point of aim. In this case, 12 clicks upward and 8 clicks to the left.

Exactly! Not just ammo either, this can save you a lot of the sighting in time. It also allows you to quickly adjust for bullet drop and wind. All it takes is some quick and simple math that even I could do in my head. Once you get a good handle on how wind affects your target at different speeds, you can wow your friends with your quick scope tweaking.

Even at distances other than 100 yards, you can make MOA adjustments. For example, let’s say your target is at 200 yards. At that point, 1 MOA is equal to 2” and at 300 yards it’s equal to 3”. What to take a wild guess what 1 MOA is at 400 yards? If you said 4 inches, you are able to extrapolate patterns better than most politicians. Bravo!

So at 50 yards, you should be thinking in ½ inch increments. With that, the 2 inch adjustment from our example before would require 4 clicks to line things up instead.

Long range shooting isn’t just about trigger control and reading the environment. Granted, that’s the vast majority of it but still. Knowing terminology and calculations, while not nearly as exciting, will help you out in the long run.