How to pick the right riflescope

If you are thinking about buying a new riflescope, you are probably already confused by the hundreds of possible choices. How can you possibly sort out the wheat from the chaff in order to get the best scope you can afford? Maybe we can point you in the right direction.

Forget that old chestnut about optics that says “you only get what you pay for.” While it still may be true to some extent, there’s a lot of bright, reliable scopes that are reasonably priced. Because some European scopes cost two or three times the price of top-of-the-line American and Japanese scopes doesn’t mean they are twice as good. Their higher price is partly due to the high wages in those countries, which is one reason why Zeiss and Swarovski are now having some of their scopes assembled in the U.S. using parts imported from Germany and Austria.

Within limits, a high price tag does give an indication of the optical quality inside a scope, but the average guy doesn’t have the wherewithall to rush out an buy the most expensive scope on the market. In any case it may, or may not be the best choice for you. There are a good many other things to consider. 

The first step is to look at what you expect the scope to do for you. If you want it for a big game rifle, that eliminates a lot of target, benchrest and other assorted models from consideration. First, how much recoil does the rifle have? Second, how whatís the price youíve budgeted for? Do you always hunt in good light? What  is the average range at which you expect to be shooting? The answer to that last question gives a good idea of the power you need. But bear in mind that where optics are concerned there’s no free lunches. You give up some field of view, light transmitting ability, eye relief and other worthwhile qualities in order to gain higher power. Where hunting scopes are concerned thatís an inevitable trade-off. It’s better to try and strike a happy medium. 

One of the best ways to narrow your choices is by drawing on your own experience. If you hunt medium-size game animals like ferals and deer, high power is less important than a wide field of view or how well the scope performs in poor light during the prime hunting times at dawn and dusk. 

Do you really need a variable-power scope? Admittedly, a versatile variable is all the rage these days, but you have decide whether you want to spend your money on a switch-power glass or perhaps a slightly better-quality fixed-power scope. Many hunters consider the 6x to be a good all around choice. 

Let’s get down to the nitty-gritty. Basing your choice on what you read on spec sheets is not the best way to calculate which of two scopes would be better for you. It makes more sense to actually look through the scopes. But you can’t tell much by looking through them in a gun shop, or even out front at midday. It’s essential that you be able to put some numerical value on which scope provides the best image for you. The visual chart we’ve reproduced here is the best way to do just that.

The reality is that there’s no way you can run the tests that manufacturers use to evaluate  their products which involves some highly sophisticated optical equipment. So you should base your choice on what you can see on the visual chart. Companies who import El Cheapo scopes won’t like this idea at all, but it’s the only practical method of determining resolving power.

Here’s how to go about it. Copy the chart and pin it to any vertical surface about 100 metres away, or if you are limited for space, you can carry out the test at 25 or 50 metres. This is hardly practical inside a gun shop, so it may be necessary to go to your local range and get the guys there to let you check some of the scopes thay have on their rifles. They’d probably be interested to find out how their scopes rate compared to some others.

Ideally use a solid rest so that you can hold the scope steady and look through it without touching it. If the scope is already mounted on a rifle, this makes it easier to set up. Have, as near as possible, even light over the Visual Check Chart. Do not pin it to a reflective surface. When setting up the scope, align it carefully, so that the reticle if it is a crosswire or dot, is in the centre of the chart. The top of a post reticle should rest at the bottom centre edge of the chart. Once the scope  is properly aligned, close your eyes for 30 seconds, then open them and read the smallest line in which you can count each letter separately. This test should give  a fairly accurate indication of the scopeís resolving ability.

Each line on the chart has a number. If you divide that number by the power of the scope you will get a ‘sharpness’ valuation that gives you a comparison to use. The higher the value of the sharpness evaluation the better. For instance, if one scope has a ‘sharpness’ value of 6 and another has 12, the scope with the 12 value is better.

As you change the power of a variable scope the smallest line you can see clearly will change, but not always in exact proportion to the change in scope power, something youíd better keep in mind. Always check a variable at several different power settings.

It may not be possible to run the tests at 100 metres. But don’t worry. Just adjust the ‘sharpness’ value by the fraction of 100 metres you are using. For instance if you carry out your tests at 50 metres, calculate the sharpness value in the same way, but divide by two to arrive at the corrected 100 metres value. 

You should be able to read the 8 line at 50 metres with the average 4x scope. A 25 metres figure would be divided by four, etc. Avoid trying to get the distance at which you test the scope a whole lot shorter than the range you expect to hunt. That could give you a misleading result.

If you are serious about getting a valid result, you should extend your testing to poor light conditions. Most of the cheaper scopes may allow you to see well under bright light conditions, and give an indistinct image in dim light. The toughest test is carried out  20 minutes before dawn and after dark. The sky in the west east is 12 candle power 20 minutes before dawn and the same intensity of light from the sky would also be true for 20 minutes after sunset. 

To evaluate the results of this test, the reader should know that with normal eyesight (20-20 vision), he can resolve the number 8 horizontal letters at 25 metres. Put another way, the width of the number 8 letters would have to be doubled for him to be able to resolve them at 50 metres. So with a 4x scope, checking it at 50 metres should resolve a figure 1/4 the size of one the unaided eye could resolve. This would be 1/4 of 12mm or a letter 3mm high. A 8x scope should resolve letters (1/8th of 12mm or 1.5mm high) a 16x down to 1/16th or 0.05mm and so on.

Focusing each scope to suit your own eyesight is vitally important as results can vary to be better or worse. This may limit your ability to compare scopes at the range, because the owner may not want you tampering with his adjustment for focus.

After you’ve done all your testing, you should be able to tell which scope has the brightest image, and the best resolving power. But you should also take into account other factors such as weight and bulk and construction. 

Bear in mind, however, that lens quality not a large objective, is the primary factor in scope brightness. The best scopes will all have fully multi-coated lenses, be wary of those marked ‘fully-coated’ or simply ‘multi-coated.’ Top makers multi- coat all lense surfaces, while often on cheaper scopes only one or two surfaces are multi-coated and all the other lenses are single-coated. Picking the best scope for your style of hunting isnít as simple as buying a particular brand. Most scopes these days are fogproof and shockproof, but many other factors are involved. So you’ll find it rewarding to spend the time and thoroughly check each scope out before you part with your hard-earned money.

This article was first published in Sporting Shooter, July 2010.