Bullet drop
From Wikipedia, the free encyclopedia
Bullet drop is the name given to the tendency of a bullet to drop in flight due to the effect of gravity. It is important to understand the ballistics of a given cartridge when zeroing the weapon. For example, Hornady lists a bullet drop of 42.40 in (1.076 m) at a distance of 500 yards (457.2 m) for a .30-06 rifle zeroed at 200 yards (182.88 m) [1]. To plan for bullet drop and compensate properly, one must understand the parabolic trajectory of the round. Once the rifle is calibrated to hit the desired mark at a given range, one can estimate where the round will be at any point along its trajectory (with the exception of windage, which is a lateral movement, as opposed to the vertical movement of bullet drop). After the trajectory is plotted, one can use a bullet drop compensator (or "BDC") to adjust the rifle without the need to fire a shot.
Note also that bullet drop need not always be a "drop". After the round leaves the muzzle, it will actually rise some distance, before settling into a ballistic trajectory. Because of this, if the same .30-06 rifle were calibrated to be "zero" at 400 yards (365.76 m), one would actually see a "rise" of 13.8 in (350.2 mm). However, this would still be 7.2 in (182.8 mm) lower than the muzzle itself. In general, smaller, faster cartridges, such as the .204 Ruger and .17 HMR are less prone to bullet drop, and more prone to windage. Conversely, heavier cartridges are less prone to windage and much more prone to bullet drop.
