Riflescopes serve a variety of functions to different users depending on the application. They obviously help the end user aim and align with the end target aiding in precise shot placement. Scopes also use multi-power magnication to aid shooters with poor or aging eyesight. There are also instances, hunters need to obtain a precise look at their game (example verify small buck or doe) before they proceed with the hunt. They also aid in the estimation of the distance of the target.

There is also a very good reason to use a riflescope on your hunting rifle or target shooter- simplicity. Scopes are not at all the fastest method of sighting your target. The fastest would be the open or iron sights that came on your rifle. However, scopes are the simplist. With the open sights, you have to align the front and back sight along with your target. Once a scope has been aligned properly, all the user needs to do is place the crosshairs  or reticle on the target.

Riflescopes are produced more powerful every year. Consumers can get caught up in the technology and can be lured into more power than they actually need and can use. The average deer rifles use riflescopes that are in the magnification range of 3x-9x. That is the scope will magnify the object 3 times to 9 times its actual size.

Listed below are common riflescope terminology and features that are used on common riflescopes.

Magnification:

Several factors and considerations go into choosing a magnification or power range. First understand that higher the magnification or power, the less light the scope will transmit.  Also higher power ranges narrows the field of view which means that through your scope at 80 yards you could be looking at a hairy patch rather than the full deer. The 3x-9x power range is a good choice for average deer rifles. Shotgun or muzzleloaders need even lower power settings of 2x due to their lower ranges.    
For long range target shooting higher power scopes such as a 6x-20x are OK.

Variable vs Fixed:

As mentioned earlier a variable power scope has an adjustable magnification range such as the 3x-9x. This means the scope has an infinite adjustment within the 3 to 9 magnifcation range. Fixed scopes are simply fixed on one magnification level such as the 3x. Some people prefer the fixed due to the simplicity. For short range applications such as small game hunting with 22 rifles the fixed scopes can be a good application. Most scopes used are variable power scopes.

Objective Lens:

The objective lens a lens in the scope that is at the output end. The objective lens are identified on a riflescope by its size namely its diameter in mm. For instance a scope with a 40 objective lens means that the diameter is 40mm. For medium range scopes a 40mm to 44mm size range is the most popular. Larger sizes are available and can have both positive and negative attributes. The larger the objective lens the more light it will transmit, however, it also increases the overall diameter of the scope making it larger and more difficult to mount. The larger the objective lens the higher, the scope will have to be mounted causing the rifle to be cumbersome to handle. Leupold has addressed this problem on their newer models by indenting the bottom of the objective lens closer to the scope. This allows a larger objective lens while maintaining the scope mounting height approximately the same.

Scope Identification:

Riflescopes are commonly identified by the magnification range and the objective lens size. For example, 3-9X40 scope means that the scope has an adjustable 3x-9x magnification range and a 40mm objective lens. Almost all the scope manufacturers identify their products in this manner.

Tube size:

Most scopes have the main tubes either 1 inch in diameter or 30mm in diameter. Knowing the main tube diameter is important in mounting and knowing what size rings to mount the scope to the rifle.

Parallax and Adjustable Objectives:

Parallax is a term used that can be hard to understand. A simpler way to look at it is the variation of the placement of the eye looking into the scope. In other words, each time you look in the scope with your eye, it will not be in the same spot. This could affect the focus of the scope. Adjustments for this is made at the objective lens and scopes with this feature is said to have adjustable objectives. This feature is generally not needed for scopes with power settings 10 or lower.

Coating:

Most scopes have coatings on their lenses. These coating quality can vary from manufacturer to manufactuer. These coatings do reduce the glare and loss of light. The more coating applied normally improve the light transmission and contrast.

Field of view:

This is simply a measurement of the left to right distance that you can see through the scope at a set distance. Normally this distance is at 100 yards. As the scope power level is increased the field of view (FOV) is decreased. As the power level is decreased the FOV is increased.

Minutes of Angle (MOA):

This is basically an option or feature on a riflescope that will adjust the point of impact of the bullet to the target. These adjustments are normally made in 1/4 inch adjustments at 100 yards. If your bullet hole is 1 inch low at a 100 yard target you can adjust by adjusting the MOA by 4 clicks which would be 1 inch at 100 yards. The adjustment is linear based off of the 100 yards. For example if the bullet is low by inch at 200 yards only 2 clicks are required to adjust.

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