Using a scope on your rifle, shotgun or pistol can greatly improve your accuracy. Just as different types of guns have different applications, so do the scopes that are available for these guns. When choosing a scope, keep in mind the type of shooting you plan to be doing and the type of weapon that the scope is for.
Variable Power Scopes
Variable power scopes are equipped with adjustable magnification settings and are practical for a variety of ranges. The first set of numbers in a variable power scope description indicates the scope's magnification range. For example, a 3-9x40 mm scope gives you a magnification range of three to nine times your normal vision and has an objective lens diameter of 40 mm. The objective lens allows light into the interior of your scope; as a general rule, the larger the objective lens, the sharper your sight picture.
Fixed Power Scopes
Fixed power scopes are preset at a specific magnification. These scopes are practical if the majority of your shooting is done at a consistent range. Fixed power scopes are generally produced with medium magnification, such as 2x, 4x or 6x. The scopes will provide you with the accuracy you're looking for, but are not as versatile as variable power scopes.
Pistol scopes function in exactly the same way the rifle scopes do; however, there is a significant difference in terms of eye relief. Eye relief is the distance between the scope's ocular lens and your eye. On a rifle or shotgun scope, eye relief is approximately 4 inches. On a pistol scope it can be up to two feet. The difference in eye relief prevents rifle and pistol scopes from being used interchangeably.
Mil-Dot scopes, also referred to as tactical scopes, feature crosshairs with range marks that can be used to estimate the distance to your target in meters (provided that you know the height of your target in meters). By counting the number of mil-dots from the bottom to the top of your target, dividing your height by that number, and multiplying your answer by 1,000, your results will be the distance in meters. For example, with the target height of 2 meters (6 feet) and a mil dot count of 4, your equation would read: 2 ÷ 4 = .5 x 1,000 = 500. Your target is 500 meters away.