Minute of Angle. Minute of angle is a term used to discuss shot dispersion. It is the standard unit of measurement used in adjusting rifle sights and other ballistic-related measurements. It is also used to indicate the accuracy of a rifle. A circle is divided into 360 degrees. Each degree is further divided into 60 minutes, so that a circle contains 21,600 minutes. A minute of angle is an angle beginning at the muzzle that would cover 2.540 cm at a distance of 91.4 meters (Figure F-16,page F-18). When the range is increased to 182.8 meters, the angle covers twice the distance, or 5.08 cm. The rule applies as range increases: 7.62 cm at 274.2 meters, 10.16 cm at 365.6 meters, and so on.
Increase of Shot-Group Size. Just as the distance covered by a minute of angle increases each time the range changes, a shot group can be expected to do the same. If there is 2.540 cm between bullets on a 25-meter target, then there will be an additional 2.540 cm of dispersion for each 25 meters of range —a 2.540-cm group at 25 meters (about 3.5 minute of angle) is equal to a 25.4-cm group at 250 meters (Figure F-17).
The 25-Meter Zero Standard (Figure F-18, page F-18). A standard E-type silhouette is about 48.26 cm wide; a circle (angle) that is 48.26 cm at 300 meters is 4 cm at 25 meters. Therefore, a soldier that can fire all bullets well within a 4-cm circle at 25 meters and adjusts the sights for zero will hit the target at all ranges out to 300 meters.
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