Choosing the Right Riflescope

By Pat Mundy - of Leupold

Choosing the right riflescope is a difficult task, only made more difficult in recent years by the continual improvements in technology. Light management, mechanical reliability, ruggedness, cosmetics, clarity, and value have improved dramatically, making many modern riflescopes into products that sportsmen and women could have only dreamed about just 50 years ago.

When shopping for a riflescope it is essential to compare construction, mechanical reliability, optical qualities, ability to reduce glare and handle light, and overall suitability to your hunting application. Never underestimate the value of a world class warranty and good customer service.

In 1947, Leupold and Stevens, an Oregon based manufacturing company, introduced the first oxygen purged, nitrogen filled riflescope. They were responding to a problem that had plagued many scopes up until that time, which was an intolerance to rapid temperature changes, which, coupled with high humidity, caused the internal lenses of a riflescope to fog. Unfortunately, this fogging was apt to happen almost any time, which meant that many scopes were very much a “good weather only” proposition and that they could never really be depended on when afield. This purging of oxygen and filling with nitrogen solved this problem and soon became the industry standard for environmental protection in riflescopes.

Today, virtually every scope manufactured claims some degree of waterproof and fogproof construction, and this is very critical to the overall performance of the scope. Absolute waterproof integrity, coupled with durable construction are especially critical for the hunter who works in extreme conditions. Rapid temperature changes, humidity fluctuations, and even variations in elevation—the hallmarks of extreme hunting, can all compromise the waterproof integrity of a scope.

Equally as important as ruggedness is the optical quality of a scope. Lens glass is carefully chosen based on its function within the scope, and of its ability to meet the optical requirements specified by optical engineers. The glass is carefully cut, and meticulously polished to remove any scratches or inclusions that could interfere with the clean passage of light through the lens. Special multicoatings (layers of metallic compounds that increase light transmission) are then applied to each lens to maximize its light transfer properties, and maintain the highest level of optical clarity. What a hunter receives from this treatment is unexcelled clarity and brightness. Contrast, color, and clarity are all enhanced to the point where it is worlds easier to spot the difference between a tan game coat and brown underbrush today than it was a generation ago.

However, lenses are only part of the optical equation. The enemy of good light management is glare, and glare is a difficult element to master. Extensive internal blackening of components, (including lens edges in some cutting-edge riflescopes), coupled with intensive grooving of the inside of the scope tube itself, causes light to be channeled properly through the scope. These treatments reduce the incidence of stray light bouncing around within the scope body to ruin image quality.

Modern riflescopes should also deliver crisp, accurate windage and elevation adjustments and a reliable point of impact across the entire power range. In years past, variable riflescopes often shifted point of impact as easily as they changed magnification. This is no longer the case, and today, most variables will deliver the same point of impact when set at 3.5x as they will when set at 10x.

Variable powered riflescopes also offer a light management advantage over fixed power scopes, in that, as you change magnification, you also change the exit pupil—which is a measure of the amount of light passing through the scope to your eye. Exit pupil is derived by dividing the diameter of the objective lens by the magnification of the optical device. The human eye can dilate from about 7mm for a young person in total darkness to 2mm in bright sunlight. Ideally, the exit pupil of the optical device should match or slightly exceed the dilation of the eye’s pupil so that the eye is receiving as much light as it can use for a given condition. This way, the image will always appear bright.

An example of exit pupil: if a hunter goes hunting with a 3.5-10x40mm scope early in the morning, and is in need of a crisp, bright image right at shooting light, he can dial his scope down to 5x, and he will receive an 8mm exit pupil (40mm divided by 5x equals 8mm exit pupil). Later in the day, when the sun is high, and area he is hunting is bright, he can turn his scope up to 10x and still receive a 4mm exit pupil (40mm divided by 10x equals a 4mm exit pupil), which is excellent for bright conditions. As evening approaches, he can turn the scope back down to 8x or so, to receive a 5mm exit pupil (40mm divided by 8x equals a 5mm exit pupil), and still have plenty of light to make a shot right at the end of legal shooting hours.

Exit pupil is dependent entirely on magnification and objective lens diameter. If magnification is increased, exit pupil will decrease, unless the objective lens diameter increases at a proportional rate. 50mm objective riflescopes will deliver a larger exit pupil, and thus, a brighter image, in poor light, all things being equal, than a similar powered scope with a smaller objective. Of course, there are other tradeoffs of a 50mm scope, such as the requirement of higher mounting, the greater weight and bulk, and the fact that a higher line of sight in relation to the bore line causes point of impact to be affected slightly. All of these factors must be considered before deciding on a scope for your brand of shooting, but in most cases, a scope that will deliver a 3.5-5mm exit pupil at the magnification you are most comfortable with for hunting will be more than adequate for most hunting tasks.

One other thing to remember is that contrary to common belief, a larger objective lens does not increase the field of view of a riflescope. It only increases the amount of light entering the scope, and, in the case of scopes using slightly less capable components, it will increase the “sweet spot” at the optical center of the lens, making images appear sharper and more crisp in the center of the field of view.

All of these factors should be considered when a hunter goes shopping. A hunter in pursuit of elk in the black timber, for example, would usually be best suited by a different riflescope then a hunter pursuing antelope on the high plains.
Field of view, magnification, and eye relief are the three elements of the “optical triangle” and they all work together to give a hunter the pleasing, full view that he needs. Heavy timber or close range shooting demands a large field of view, which is dependent on lower magnification. So, an elk hunter or coastal deer hunter might prefer a 2-7 variable, with the ability to set the magnification on 2x for “up close and personal” shooting, and still increase the magnification to 7x if a 200 yard shot across a clear-cut presents itself. A hunter pursuing sheep or pronghorns, on the other hand, may prefer a 4.5-14, since he or she is less apt to take a close shot, and more likely to have to take one of longer range, where magnification will aid in the surgical shot placement necessary for a quick, clean kill.

Varmint hunting demands higher magnification, as shots can usually be very long, and targets are very small. Because most varmint rifles don’t recoil much, eye relief can be sacrificed for magnification. Eye relief of 3.5 inches or more is ideal for use on rifles that have much recoil, and four inches is even better. This will deliver a full sight picture, and at the same time keep the objective lens out of a shooter’s eyebrow during recoil.

Never overlook reticle choice, either. Flexible reticles, such as the Duplex® invented by Leupold over 40 years ago, lead the shooter’s eye naturally to the center of the aiming point and are ideal at close range or in heavy cover. Lighter or finer variations of the same reticle provide good range estimating capabilities, and also deliver the fine aiming point necessary for longer range, more precise shooting that is typical of much western hunting and varminting.

In more recent years, reticles have further matured, into some of the more complex (yet extremely capable) range estimating reticles we see today. Some examples include reticles designed for tactical applications, such as the Mildot, Horus Vision reticle, and some of the reticles employed by Nightforce. Each of these reticles provide many aiming points, or a grid to make very long range hits easier. For the hunter, reticles such as the Ballistic Plex, Boone & Crockett Big Game reticle, Varmint Hunters Reticle, or TDS reticle all provide simple, yet very capable methods of making hits at the longest ethical ranges—with practice.

Many of today’s riflescopes use 30mm main tubes. The 30mm tube provides both more strength and, usually, considerably greater latitude of windage and elevation adjustment. More latitude makes it easier to get zeroed at the range, and for those shooters who love to shoot long distance, it allows you to “dial up” to be on target at longer ranges.

Finally, never forsake a good warranty. Obviously, the best warranty is one you never have to use, but in the rare instance that a scope does go south, it is good to be covered by product service that is fast, reliable, friendly, and free.
Today’s riflescope market is full of good choices. Optical products in general, and riflescopes in particular, have changed dramatically over the last couple of generations. No one benefits more from this than today’s hunter, who has more good choices than ever when he or she walks into a store looking for a reliable, effective product. Consider the above criteria, along with the game and terrain you hunt, when making your choice, and in most cases, you will purchase a product that will be with you for a lifetime of rugged hunts and fond memories.