Recoil Magazine, the premier firearms magazine, just published an article of mine on understanding Minutes of Angle (MOA) and Mils. You can head over to their website for the preview of MOA vs. Mil and you can read the full article by picking up Issue 23 at your local retailer or by subscribing on their website.
In the article, I cover what MOA and Mils are and how to use them in long range shooting. These topics and more are explained in greater detail in my book, the Long Range Shooting Handbook.
Why is this an update on the website for a law practice? Simply, I shared it to help reinforce that I am a true gun-guy and a firearms industry insider who actually understands firearms and their use as much as I know firearm laws.
Bear With Us, ’Cause it’s Time to Get Your Math On
The argument over whether to use Minutes of Angle (MOA) or milliradians (mil) is one that’s guaranteed to spark a lively online debate among shooters. Before you get sucked into the fray, arm yourself with a healthy understanding of the difference between the two systems, and how to make them work for you.
Both MOA and mils are units of angular measurement. In shooting, angular measurements are used to describe linear size, relative to distance (e.g. 10 inches tall at 300 yards, or 15 centimeters left at 200 meters). The most common uses are incremental adjustments to a bullet’s impact, estimating the distance of a known-size target, “holding” for windage or elevation, and measuring accuracy by shot-group size.
The most important thing to understand about these measurements is that they are angular! For example, when we adjust our scopes we move the reticle inside the scope, which then forces us to move the barrel ofthe rifle up, down, left, or right in order to get the reticle back on to the target. This difference between where the rifle’s barrel was pointed prior to an adjustment in windage or elevation and where the barrel is pointed after the adjustment can be measured as a change in angle.
To help you understand how an angular measurement translates into different sizes at different distances, imagine holding two laser pointers next to each other and pointing them down range. If you spread the two laser pointers apart at a certain angle, the lasers would gradually get further and further apart from each other as they went down range. For any given angle, however, the rate at which the dots spread apart is consistent — the dots will be twice as far apart at 200 yards and 10 times as far apart at 1,000 yards as they were at 100 yards. See Figure 1.
Minute of Angle (MOA)
In the term Minute of Angle, the word minute means 1/60th (for example, 1 minute of time is 1/60th of one hour) and the word angle refers to one of the 360 degrees in a circle. So, 1 Minute of Angle is 1/60th of a degree. (See Figure 2.)
If we spread the two laser pointers from the example above apart 1 MOA (1/60th of a degree), then the two lasers’ dots would be about 1 inch apart at 100 yards, about 2 inches apart at 200 yards, about 3 inches apart at the 300 yards and so on. Simply stated, this means that 1 Minute of Angle is about 1 inch per 100 yards. I say “about” 1 inch because 1 MOA is actually 1.047 inches per 100 yards, but using 1 inch per 100 yards is close enough for our purposes. Cue the slapfest. Many will argue that it’s crucial to use 1.047 inches per 100 yards, and if you don’t it’ll make the baby Jesus cry.
I don’t disagree that it’s more accurate; it’s just that in the real world I don’t notice enough of a difference to use the more accurate number, but hey, maybe you do. Let me qualify that. At 1,000 yards, when I use 1 inch per 100 yards, 1 MOA equals 10 inches. When 1.047 inches per 100 yards is used, 1 MOA equals 10.47 inches. The 0.47 inch difference at 1,000 yards is barely wider than the width of my .308 Win bullet and is so small that you can’t even adjust for it on a scope (the finest most scopes adjust is ¼ MOA, which is about 2.5 inches at 1,000 yards). Therefore, even if I needed to move my bullet’s impact up 11 inches at 100 yards, the closest adjustment I can make is up 1 MOA.