Compensation for gravity. The firer must compensate for the effects of gravity to engage high-priority targets. The objective of the battlesight zero is to find a zero range that allows for target engagement out to the maximum possible range while requiring minimum adjustments to the aiming point. A study of M16 trajectory data reveals that setting the sights to hit at 250 meters is the best compromise for hitting all targets from 0 to 325 meters without major adjustments to the aiming point. As shown in Figure F-2B, the bullet stays close to the line of sight, but this has been accomplished by pointing the bore well above the target. The bullet drop from the bore line applies equally in this figure. The bore is actually pointing 16 inches above the aiming point at 250 meters and 24 inches above the point where the bullet will strike at 300 meters. With graphics showing only line of sight and trajectory, it appears that the bullet rises and then falls, but this is not true. The bullet's line of departure is the bore line, and it always drops from that line as shown in Figure F-2A The line of sight and bullet trajectory actually coincide at 42 meters (the bullet starts out about 2.6 inches below the sights) and again at 250 meters, giving the illusion that the bullet rises and falls.
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