MOA is MOA

When teaching marksmanship, a concept that many students have difficulty grasping is that of "Minutes of Angle" - MOA. This article is a primer on MOA.

Definition
A complete circle can be divided into 360 equal units - degrees. Each degree can be further subdivided into 60 equal units - minutes. Each minute can be further subdivided into 60 equal units - seconds.

Therefore, a minute is a unit of measurement. Technically speaking, a minute is 1/21,600th of a circle. It's a measurement of how wide an angle is.

As luck would have it, a minute stretched out to 100 yards away, is really close to 1 inch - 1.047" to be more precise.

Common Errors
Many in the shooting world will see a 1 inch group and say that it is "Minute of Angle." This statement is roughly correct if the group was shot from 100 yards. If it is shot from a different distance, then the statement is not at all correct.

If you shoot a 1 inch group at 25 yards, then the group is 4 Minutes of Angle wide. 4 MOA.

If you shoot a 1 inch group at 300 yards, then that was 0.33 Minutes of Angle wide. 1/3 MOA.

Close Range
If you are shooting at 100 yards, then measuring the MOA of your group is relatively easy - just measure the inches between the farthest shots and you pretty much have it.

Understand though, that if you are closer than 100 yards, then the MOA "cone" shrinks:
- 1 MOA at 75 yards = 0.75 inches.
- 1 MOA at 50 yards = 0.5 inches.
- 1 MOA at 25 yards = 0.25 inches.

Long Range
If you are shooting at 100 yards, then measuring the MOA of your group is relatively easy - just measure the inches between the farthest shots and you pretty much have it.

If you are shooting past 100 yards, the MOA cone is expanding.
- 1 MOA at 200 yards = 2 inches.
- 1 MOA at 400 yards = 4 inches.
- 1 MOA at 1000 yards = 10.47 inches.

Why This Is Important
Because most optics have adjustments in MOA.
* A Rifleman needs to measure the group - specifically, how far off target a group is.
* Then the Rifleman calculates MOA.
* Then the Rifleman applies the correct number of clicks to the sighting device.

Being a Rifleman means no guesswork. Only measurement, calculation, and application.

Example 1
You have a scope that states 1/2 MOA per click. From a steady position at 100 yards, you fire a group that is close together, but is not close to the center of the target. It measures 9 inches above target center, and 4 inches to the right.

You know that at 100 yards, 1 inch is approximately the same as 1 MOA.

You calculate that you need to apply 9 MOA of downward elevation and 4 MOA of left windage to be at the middle.
- Since the rifle scope states 1/2 MOA per click, you apply 18 clicks down and 8 clicks left adjustment.
- You fire another group and have success!

Example 2
Your rifle is zeroed at 25 yards. You take this scope out to 200 yards and find that the group measures 5 inches above the center of the target.

You know that at 200 yards, 1 MOA is approximately 2 inches. Therefore, you calculate that you are 2.5 MOA high.

Again, with a scope having 0.5 MOA per click, you know that you will have to apply 5 clicks down elevation to be on target. You apply it, and fire another group which is in the middle of the target.

Example 3
You are firing from 25 yards. The group is tight, but it is 1.5 inches low, and 4.5 inches to the left.

You know that 1 MOA at 25 yards is 0.25 inches. Therefore, you calculate that your group was 6 MOA low, and 18 MOA to the left. 

This optic has 1/4 MOA adjustments, so you apply 24 clicks up elevation and 72 clicks right windage. Now it's on the money!