Scope IDs

Question
Hello Mr. Bob, I am looking to buy a scope for my new mini 14. I have been looking in magazines to buy one and am not sure what to buy because I'm not sure what for example 3-9X40 means. Please clarify this and also if you could explain what for example 1/2 MOA is. I woild greatly appreciate this. Thank you.

Answer
Hello Casey.

There are literally hundreds of different scope models and options to choose from but most of the core features are easily explained. Here are some tips:

The first number(s) usually refer to the magnification power. If only one number such as 4x25mm then it is a fixed power scope with a magnification factor of 4. So an object which is 100 yards away would appear to be only 25 yards away when viewed through the scope. If a second number or a range is given such as 3-9, this indicates a variable power scope which is adjustable from 3 to 9 magnification. There is a dial or knob on these scopes to let you adjust, similar to using the zoom lens on a camera. 3-9 is a very common zoom range because it offers a lot of flexibility at the most common shooting distances ranging from 10-200 yards or even a bit more. Some scopes can go as high as 40 or more on the magnification but these would be designed for extremely long distance shooting or spotting.

The second number refers to the diameter of the objective or front lens on the scope. So a 4x25mm scope has a front lens which is 25mm wide, and a 3-9x40 has a front lens which is 40mm wide. The larger lenses collect more light thus you can see more area in your view at one time and the picture that you see is brighter, which is helpful at dawn, dusk, or shooting at night with spotlights or other artificial lighting. The smaller lenses can be more compact for travel or storage and they are generally less expensive thus they are normally only used for closer distances or occasional target shooting.

MOA stands for minute of angle. It refers to the ability to adjust the scope's point of aim, usually with small knobs or dials which move the crosshairs or reticle slightly from side to side or up/down. Making an adjustment of 1 MOA would move your point of aim approximately 1" at 100 yards. Higher quality scopes are designed for precision accuracy at longer distances so they are often adjustable down to 1/4 or even 1/8 MOA but you may not need this degree of precision for closer distances or occasional target shooting.

Other variables in scope design and quality include the materials used to make the tube: aluminum, titanium, steel, etc. and the quality of the glass used to make the lenses. There are also many different types of crosshairs or reticles including some which offer illumination in red or green for shooting in low light or when shooting in heavily wooded areas where there will be a lot of green foliage.

The following site offers a much more comprehensive guide to scope features and selection:
http://www.opticsplanet.net/how-to-choose-riflescope.html

I hope this information helps you. Good luck!

Bob