Fm

Effects of wind are much greater at longer ranges; however, they are uniform in relation to speed—for example, a 5-mph full-value wind would have exactly one-half the effect shown in the figure, moving the bullet 5 inches at 250 meters, then 10 inches, and so on. A wind of greater speed would move bullets at all ranges 1 1/2 times more than a 10-mph wind, or 7 1/2 inches at 175 meters. The same rule also applies to a half-value wind. A 5-mph half-value wind would move bullets one-fourth the amount shown in Figure F-9—3 3/4 inches at 300 meters.

An easy way to remember the effects of wind is that a 10-mph wind moves the bullet 10 inches at the battlesight zero range of 250 meters. If this information is taken to the standard field fire range with targets at 75, 175, and 300 meters, it is easy to remember that a 10-mph wind moves the bullet 1,5,10, and 15 inches at the ranges of 75,175,250, and 300 meters, respectively. These numbers can be converted to a 1-mph wind —1/10 inch at 75 meters, 1/2 inch at 175 meters, 1 inch at 250 meters, and 1-1/2 inches at 300 meters —so that when the wind speed has been determined, it can be multiplied with the mph figure to determine bullet displacement.

0 0

Post a comment