Marksmanship: Precision & Accuracy

Marksmanship is verbosely defined as the skilled manipulation of a firearm to consistently generate impact of fired projectiles on an intended location. More simply, marksmanship is the skill of accurately hitting a target with a firearm. This will be the first in a series discussing marksmanship, but before we get into the techniques, we should discuss some basic concepts: precision & accuracy.

Marksmanship can be evaluated with two metrics, precision and accuracy. Accuracy is the degree of veracity (hitting the desire mark) while precision is the degree of consistency (repeatability of results). Key to being able to measure these metrics is the concept of a group, which is simply a series of shots fired under the same conditions.

Groups

A group is a series of at least three shots fired from the same stance, point of aim, grip, and eye relief. Typically, the greater number of shots a group contains the more useful the data becomes. From a coaching perspective, a higher number of rounds in the black can help inspire confidence.

The types of information that can be pulled from group data and comparison include the affects of wind, poor trigger control, and poor natural point of aim among others, but I'll cover how to identify and correct improperly executed fundamentals of marksmanship in a future article.

Groups are measured by the angular dispersion of the shots, or the distance between the two farthest impacts. The most precise method to measure the distance between two shots is to measure from the outside of each impact and then subtract the diameter of the bullet (be sure both values are in metric or imperial units before subtracting). Angular dispersion measured by the length of the distance is reported alongside the range of the target. For example: a 1 inch group at 100 yards or in the shorthand for of 1"@100yds.

Minutes of Angle

Angular dispersion can also be measured by minutes of arc, or minute of angle (MOA) as the industry refers to it. A minute is an angular measurement that is equal to 1/60 of one degree[1], much like a minute of time is also 1/60 of an hour. As a historical aside, the minute has survived since the Babylonians performed astronomical calculations with the sexagesimal (base-60) system[2].

The width of a minute of angle at 100 yards is equal to 1.047 inches. Since MOA at 100 yards is very close to exactly 1 inch, many shooters use a simplified version known as SMOA (shooter's minute of angle) for calculating adjustments during fire where SMOA equals 1 inch at 100 yards. SMOA is fine for short range work, but may be error prone for precision fire beyond 1000 yards.

Because MOA is an angular measurement, it is independent of the resolution of range. So at 200 yards, 1 SMOA is equal to 2 inches; 300 yards 1 SMOA is 3 inches, ad infinitum. This makes it easy to extrapolate group sizes for different ranges. So theoretically, a 2 inch group at 100 yards would open up to 4 inches at 200 yards, but keep in mind the group is still only 2 SMOA. Ryan Cleckner of the National Shooting Sports Foundation talks more about MOA in the excellent video above.

High Precision - Low Accuracy

Precision

Precision is the measurement of the group and is independent of how close that group is to the desired target. It is a measurement of consistency and reproducibility. It is the most important metric of marksmanship as once a firearm and shooter can reliably create tight groups, bring those groups to bear on target is a relatively simple affair.

Low Precision - High Accuracy

Accuracy

Accuracy is the measurement of how close the group is to the desired target. Ideally, shots are both accurate and precise, as one without the other is ineffective. However, once a shooter obtains a precise group, one only needs to adjust the point of aim to bring precision to bear on the target. This is why most sights and optics have adjustments in MOA.

Next: Fundamentals

The next article in this series will deal with the fundamentals of marksmanship: breathing, trigger control, sight alignment/picture, and position.

References

[1] Minute of arc is a measurement of angle.
[2] Babylon mathematics gave us minutes and seconds.
[3] The science of accuracy & precision.