Wind Speed And Direction

The effects of wind vary depending on changes in wind speed and direction. Wind is classified by the direction it is blowing in relationship to the firer/target line. The clock system is used to indicate wind direction and value (Figure F-8, page F-8). Winds that blow from the left (9 o'clock) or right (3 o'clock) are called full-value winds, because they have the most effect on the bullet. Winds that blow at an angle from the front or rear area are called half-value winds, because they have about one-half the effect on the bullet as full-value winds. Winds that blow straight into the firer's face or winds that blow straight into the target are termed no-value winds, because their effect on the bullet is too small to be concerned with.

Figure F-9, page F-8, illustrates how the effects of wind on the bullet are similar to the effects of gravity—as range increases, the effects of wind increase.

A 10-mph full-value wind moves an M16A1 (M193) bullet about 1/2 inch at 25 meters to about 46 inches at 475 meters. (Using the data presented, wind effects for all

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