The area of the target covered by the rifle's front sight post can be used to estimate range to a target. A Marine notes the appearance of the front sight post on a known-distance target. A Marine then uses this as a guide to determine range over an unknown distance. Because the apparent size of the target changes as the distance to the target changes, the amount of the target covered by the front sight post varies based on the range. In addition, a Marine's eye relief and perception of the front sight post affect the amount of the target that is visible. To use this method, a Marine must apply the following guidelines:
i The front sight post covers the width of a man's chest or body at approximately 300 meters. i If the target is less than the width of the front sight post, the target is in excess of 300 meters and the rifle's BZO cannot be used effectively. i If the target is wider than the front sight post, the target is less than 300 meters and can be engaged point of aim/point of impact using the rifle's BZO.
See figure 10-3.
Figure 10-3. Front Sight Post Method. Visible Detail Method
The amount of detail seen at various ranges can provide a Marine with an estimate of the target's distance. To use this method, a Marine must be familiar with the size and various details of personnel and equipment at known distances. Visibility (such as weather, smoke or darkness) limits the effectiveness of this method. A Marine should observe a man while he is standing, kneeling, and in the prone position at known ranges of 100 to 500 meters. He should note the man's size, characteristics/size of his uniform and equipment, and any other pertinent details. The Marine then uses this as a guide to determine range over an unknown distance. A Marine also should study the appearance of other familiar objects such as rifles and vehicles. To use this method, a Marine applies the following general guidelines:
i At 100 meters, the target is clearly observed in detail and facial features are distinguished i At 200 meters, the target is clearly observed. There is a loss of facial detail. The color of the skin and equipment are still identifiable.
i At 300 meters, the target has a clear body outline, face color usually remains accurate, but remaining details are blurred.
i At 400 meters, the body outline is clear, but remaining detail is blurred.
i At 500 meters, the body shape begins to taper at the ends, and the head becomes indistinct from the shoulders.
i At 600 meters, the body appears wedge-shaped and headless.
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