Rifle scopes give shooters the benefit of extending their vision far beyond normal reach of their eyesight. Most scopes can also be used to determine range, through the use of a little math. Rifle scopes either have a fixed power setting or variable power settings which give the shooter the versatility of viewing objects at different magnifications.
Scopes are produced with either a fixed power setting or an adjustable power setting. Fixed power scopes are preset at a specific magnification. Adjustable power scopes allow the shooter to set the magnification as the situation dictates. The power can be adjusted by turning the variable power ring (adjacent to the eyepiece) to the desired magnification.
The intersection of the scope cross-hairs should be on the bullet's projected point-of-impact. The cross-hairs can be adjusted by using the dials on the top and the right hand side of the scope (the top dial adjusts the horizontal cross-hair and the right-hand dial controls the vertical cross-hair).
Parallax Error Correction
Parallax error is the illusion of target movement produced by a shift in the line-of-sight through the scope. Parallax error can become a factor at longer ranges. Adjustment for parallax can usually be done on the objective bell (provided the scope has an adjustment). To adjust for parallax, change the setting on the objective bell to the target distance.
Many scopes have ranging marks on the scope's cross-hairs that can be used for estimating range. To use these marks, you must know the height of your target in meters, count the number of marks to the top of your target and know a simple algebra equation. The combination of these three variables will result in the range in meters.
Estimate the range by dividing the target height by the number of tick marks and multiplying the answer by 1,000. For instance, if the target is 3 m high and the tick mark count is 2, then the equation would look like this: (3 ÷ 2) x 1,000 = 1,500. Your range to target is 1,500 meters.
- hunting rifle with optic image by Aleksandr Ugorenkov from Fotolia.com