Editing Sniper (section)

===Range finding===
The range to the target is measured or estimated as precisely as conditions permit and correct range estimation becomes absolutely critical at long ranges, because a bullet travels with a curved [[trajectory]] and the sniper must compensate for this by aiming higher at longer distances.<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}} If the exact distance is not known the sniper may compensate incorrectly and the bullet path may be too high or low. As an example, for a typical military sniping cartridge such as [[7.62×51mm NATO]] (.308 Winchester) M118 Special Ball round this difference (or "drop") from {{convert|700|to(-)|800|m|yd|sp=us}} is {{convert|200|mm}}. This means that if the sniper incorrectly estimated the distance as 700 meters when the target was in fact 800 meters away, the bullet will be 200 millimeters lower than expected by the time it reaches the target.<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}}

[[Laser rangefinder]]s may be used, and range estimation is often the job of both parties in a team.<ref name="Plaster 2006">{{harvnb|Plaster|2006|p=346}}</ref> One useful method of range finding without a laser rangefinder is comparing the height of the target (or nearby objects) to their size on the mil dot scope, or taking a known distance and using some sort of measure (utility poles, fence posts) to determine the additional distance. The average human head is {{convert|150|mm|sp=us}} in width, average human shoulders are {{convert|500|mm|sp=us}} apart and the average distance from a person's pelvis to the top of their head is {{convert|1000|mm|sp=us}}.

To determine the range to a target without a laser rangefinder, the sniper may use the [[Angular mil|mil]] dot [[reticle]] on a scope to accurately find the range. Mil dots are used like a [[slide rule]] to measure the height of a target, and if the height is known, the range can be as well. The height of the target (in yards) ×1000, divided by the height of the target (in mils), gives the range in yards. This is only in general, however, as both scope magnification (7×, 40×) and mil dot spacing change. The USMC standard is that 1 mil (that is, 1 milliradian) equals 3.438 MOA ([[minute of arc]], or, equivalently, minute of angle), while the US Army standard is 3.6 MOA, chosen so as to give a diameter of 1 yard at a distance of 1,000 yards (or equivalently, a diameter of 1 meter at a range of 1 kilometer.) Many commercial manufacturers use 3.5, splitting the difference, since it is easier to work with.<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}}{{verify source|date=June 2016}}

It is important to note that angular mil (''mil'') is only an approximation of a [[milliradian]] and different organizations use [[Angular mil#Definitions of the angular mil|different approximations]].

At longer ranges, bullet drop plays a significant role in targeting.<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}} The effect can be estimated from a chart, which may be memorized or taped to the rifle, although some scopes come with [[telescopic sight#Bullet drop compensation|Bullet Drop Compensator]] (BDC) systems that only require the range be dialed in. These are tuned to both a specific class of rifle and specific ammunition. Every bullet type and load will have different [[ballistics]]. .308 Federal 175 grain (11.3 g) BTHP match shoots at {{convert|2600|ft/s|m/s|abbr=on}}. Zeroed at {{convert|100|yd|m|-2}}, a 16.2 MOA adjustment would have to be made to hit a target at {{convert|600|yd|m|-2}}. If the same bullet was shot with 168 grain (10.9 g), a 17.1 MOA adjustment would be necessary.<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}}

Shooting uphill or downhill is confusing for many because [[gravity]] does not act perpendicular to the direction the bullet is traveling. Thus, gravity must be divided into its component [[Euclidean vector|vector]]s. Only the fraction of gravity equal to the [[cosine]] of the angle of fire with respect to the horizon affects the rate of fall of the bullet, with the remainder adding or subtracting negligible velocity to the bullet along its trajectory. To find the correct zero, the sniper multiplies the actual distance to the range by this fraction and aims as if the target were that distance away. For example, a sniper who observes a target 500 meters away at a 45-degree angle downhill would multiply the range by the cosine of 45 degrees, which is 0.707. The resulting distance will be 353 meters. This number is equal to the horizontal distance to the target. All other values, such as windage, time-to-target, impact velocity, and energy will be calculated based on the actual range of 500 meters. Recently, a small device known as a cosine indicator has been developed.<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}} This device is clamped to the tubular body of the telescopic sight, and gives an indicative readout in numerical form as the rifle is aimed up or down at the target.<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}} This is translated into a figure used to compute the horizontal range to the target.

Windage plays a significant role, with the effect increasing with wind speed or the distance of the shot. The slant of visible convections near the ground can be used to estimate crosswinds, and correct the point of aim. All adjustments for range, wind, and elevation can be performed by aiming off the target, called "holding over" or [[Kentucky windage]].<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}} Alternatively, the scope can be adjusted so that the point of aim is changed to compensate for these factors, sometimes referred to as "dialing in". The shooter must remember to return the scope to zeroed position. Adjusting the scope allows for more accurate shots, because the cross-hairs can be aligned with the target more accurately, but the sniper must know exactly what differences the changes will have on the point-of-impact at each target range.<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}}

For moving targets, the point-of-aim is ahead of the target in the direction of movement. Known as "leading" the target, the amount of "lead" depends on the speed and angle of the target's movement as well as the distance to the target. For this technique, holding over is the preferred method.<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}} Anticipating the behavior of the target is necessary to accurately place the shot.<ref name="Plaster 1993 p. "/>{{page needed|date=February 2018}}