In simple terms, a rifle scope is a tube with internal magnifying lenses that is affixed to a firearm, usually a rifle. The scope’s purpose is to help a shooter aim more accurately when firing at distant targets. Depending upon the manufacturer, model and quality of the lenses and other components, rifle scopes range in price from less than $50 for a basic scope to $12,000 for a Hensoldt Zeiss Sniper Auxiliary Model, or “SAM.” Regardless of the cost, all rifle scopes will work adequately at close range — it’s at distances of 300 yards or more that a high-quality precision scope is needed for accurate shooting.
History of the Rifle Scope
Dating back to the 17th century, refractory telescopes led to the development of the first telescopic rifle sights in 1835. By 1855, improvements such as the inclusion of achromatic lenses similar to those used in conventional telescopes were added, and windage and elevation adjustments were also improved.
Variable power scopes first appeared in the late 1940s. These early versions often didn’t reset to zero after windage and elevation adjustments and were susceptible to fogging over from damp weather and altitude. Several years later, variable power scopes became reliable enough to be accepted by shooters. Around 1960, waterproof scopes that prevented fogging were available.
Rifle scope design has remained basically unchanged since the 1960s, although some refinements have been made, such as anti-reflection lens coatings, parallax adjustments and illuminated reticles that extend morning and evening shooting times. Crosshair reticles have also been improved, including adaptations of the military’s mil-dot rangefinder system.
Perhaps the most significant change in scope design was Swarovski Optik’s 1997 introduction of the LRS telescopic sight, which integrated laser technology into the scope that could accurately measure distances up to 600 meters. Although LSR scopes are no longer produced, technologically improved rifle scopes with laser range finders are available from Bushnell and Burris.
Anatomy of a Rifle Scope
Inside the tube, or body of the scope, there’s a lens toward the front that lets in light called the objective lens. At the rear of the body is the ocular lens, which is what allows the shooter to see the target. There’s a focus lens behind the objective lens that helps sharpen the sight picture, and between the two is an erector tube that houses the magnification lenses and reticle, or crosshair assembly used to aim the rifle. The image seen by the shooter is enlarged when the magnification lens is moved toward the objective lens, and it’s reduced when the magnification lens is moved closer to the ocular lens.
The reticle can be mounted either in front of or behind the magnifying lenses, which affect what the shooter sees when magnification adjustments are made. If the reticle is in front of the magnification lens, the crosshairs will appear to change size as magnification is increased, while the target image remains the same, irrespective of the magnification setting. Reticle sizes in scopes located behind the magnifying lens remain constant regardless of the magnification setting.
The lenses and reticle assembly are held in place by the scope’s body, which is usually a lightweight, corrosion-resistant aluminum tube that’s been sealed to prevent moisture from entering and fogging the lenses. The wider area at the front scope tube holds the objective lens and is called the objective bell. At the other end of the scope tube is the ocular bell, which houses the ocular lens. The portion of the tube between the ocular and objective bells is called the main body, which is where rings that secure the scope of the rifle are attached. Most tubes have 1” diameter main bodies, although there are exceptions, so when ordering scope rings, it’s important to confirm that the ring size and main body are a match. Many long range and premium level rifle scopes will have a 30″ or 34″ main body diameter which is slightly bigger than the 1″ tube allowing more light into the scope, making for a brighter sight picture.
Target Turrets and Scope Adjustments
The main body also has knobs called target turrets that are used to make quick sighting adjustments while shooting in the field or at the range. Typically, the top knob adjusts the elevation by moving the bullet’s impact point higher or lower. The knob on the scope’s right side adjusts for windage, which determines how far left or right the bullet will strike. Together, the windage and elevation knobs fine-tune the reticle’s position to match the rifle’s aiming point with the crosshairs. Windage and elevation knobs usually have click adjustments that the shooter can feel with each turn of the knob. One click is normally ¼ minute of angle.
The two most common scope adjustment measurement systems are the Minute of Angle, or MOA, and the milliradian, or MRAD, which is also sometimes abbreviated as mil or mils.
The Minute of Angle is 1/60th of a degree, and is the most commonly used system due to its association with inches; one MOA closely corresponds to one inch at a distance of 100 yards. Because the MOA’s adjustment increments are as small as ¼ inch or less at 100 yards, MOA scopes have more precise zeroing capabilities than Milliradian scopes. Calculating MOA distances at ranges of more than 100 yards, however, is somewhat complex, and works best when coupled with a screw-adjustable BDC or duplex reticles. MOA rifle scopes are sometimes paired with a mil dot reticle, although the match isn’t the most efficient use of the mil-dot reticle system.
Similar to Minutes of Angle, a milliradian is a fraction of an angle. A milliradian is 1/1,000th of an inch, which equates to approximately 3.6 inches at 100 yards. Although it sounds more complicated than MOA, the adjustments are actually much simpler, since milliradian scope reticles are used much like an ordinary ruler. If you see through the scope that the bullet struck 1.2 mils below the center crosshairs, simply adjust the sight 1.2 mils up, and the next shot should be spot on.
Since there is no need to calculate a linear measurement from an angular one with an MOA system, the adjustment process is the same at any distance. As an example, a ¼ MOA adjustment means a 1/4 inch shift at 100 yards and would require a ½ inch shift at 200 yards. This sounds simple enough but can become complicated when calculating adjustments for odd-numbered distances. MRAD overcomes the need to mathematically calculate adjustments since the reticle is readily visible and has an easily readable scale. Favored by a majority of long-range shooters, milliradian adjustments are found only on mil reticle scopes. Hunters, however, sometimes find that the MRAD’s exposed adjustment knobs can be cumbersome to use in the field.
Interpreting and Understanding a Rifle Scope’s Specifications
It’s easy to learn about a telescopic sight’s technical specifications just by looking at the box once you know how. Also found in product descriptions in catalogs and on the Internet, a scope’s basic specifications are expressed in an industry standard format that reveal its magnification power and objective lens diameter stated in millimeters separated by an “x” symbol. As an example, a 3×40 scope is a fixed power scope that will magnify the target image by a power of three, making it appear three times larger than it would to the naked eye. The second number refers to the diameter of the forward, or objective lens, which in this example is 40 millimeters. A rifle scope marked 3-9×50 means it is a variable power scope that can be adjusted for magnification levels from three through nine, and has a 50 millimeter objective lens.
Eye Relief, Exit Pupils and Light Transmission
Eye relief is the distance the shooter’s eye can be from the surface of a scope’s ocular lens and still see a full, clear picture of the target. If the shooter’s eye is beyond the eye relief distance, the field of view is reduced. Usually, the higher the magnification and the larger the field of view, the shorter the eye relief measurement.
The exit pupil is the width of the light cone that reaches the shooter’s eye at the same distance as a scope’s eye relief measurement. The larger the exit pupil, the brighter the image will appear when viewed through the scope. To see a scope’s exit pupil, hold it at arm’s length, and you’ll notice a small circle of light in the eyepiece, which is the exit pupil. To calculate the size of a scope’s exit pupil, divide the objective lens’ diameter expressed in millimeters by the scope’s magnification power. As an example, the exit pupil of a 4x32mm scope is 8mm, which is computed by dividing the lens’ 32mm diameter by the scope’s 4x magnification power.
Most people’s eyes are affected by age, and shooters are no exception. Older people’s pupils dilate less and more slowly, which affects the sharpness of the target image and makes eye relief an important consideration when shopping for a scope. An exit pupil that’s larger than the pupil of the shooter’s eye, however, means that a portion of the light cone — and therefore the image — is outside his or her field of vision. An exit pupil smaller than the shooter’s eye pupil allows for viewing everything within the light cone, but can’t tolerate much lateral eye alignment error, which can directly affect shooting accuracy.
Light transmission refers to the percentage of available light that travels through the scope and actually reaches the shooter’s eye, which is always reduced at least slightly in the process. The three factors that affect light transmission are the quality of lens glass, the presence or absence of anti-reflective coatings and the configuration of the lenses within the scope body. High-end, more expensive scopes can at least theoretically provide a 98% light transmission. Most scopes transmit about 90% of the available light, and light transmission of 95% is considered very good.
Objective Lens Size and Tube Diameter
The next items to consider when shopping for a rifle scope are the objective lens size and the scope tube’s outer body diameter.
The objective lens size determines the amount of ambient light surrounding the target that reaches the shooter’s eye and brings the image into focus. The larger the objective lens, the more light that’s transmitted, resulting in a brighter and clearer image of the target. Larger objective lenses usually go hand-in-hand with higher magnification although, practically speaking, it is only at magnifications of 12x or greater that the difference between a 40mm and a 50mm objective lens is noticeable.
Large objective lenses are superior from the standpoints of image clarity and brightness. Larger lenses, however, need to be mounted higher above the rifle’s action and barrel than lower objective lenses. This can result in the shooter having difficulty maintaining correct cheek-to-stock contact, which can negatively affect shooting accuracy. The issue can be easily and inexpensively resolved by purchasing a built-up cheek rest.
A potential drawback to scopes with large objective lenses is their overall size and weight, which make them heavier and bulkier than scopes with smaller objective lenses. This can both adversely affect the rifle’s balance, and also make it more susceptible to bumping into objects, potentially leading to loss of zero sighting or a cracked lens.
Most scope tube bodies are either 1” (25.4mm) 30mm or 34mm in diameter, with 1” being by far the most common. The slightly larger 30mm and 34mm scope bodies are preferred by long-range hunters and target shooters typically firing at distances of 500 yards or more because they can accommodate larger lenses and have greater internal adjustment ranges. For the majority of shooters, the choice between a 1” or 30mm scope comes down to personal preference.
Parallax
Parallax effect is when the object’s position or direction seems to change when viewed through a lens from different positions. Parallax in rifle scopes makes the reticle appear to shift when the shooter’s head moves even slightly, leaving the scope incapable of focusing the target and reticle on the same plane. The result can be bad groupings or missed shots.
Inexpensive rifle scopes are usually pre-set to be free of parallax at certain fixed distances, such as 100 yards, but are unable to correct parallax at either shorter or longer distances. This is not a problem with lower magnification scopes, since any reticle shift will be too small to be noticed. Scopes of 12x or more, however, should come with a parallax adjustment, or side focus knob, which is typically located on the left, opposite the scope’s windage turret.
A simple method of checking for parallax effect is to nod your head slightly up and down while looking through the scope; if the crosshairs seem to shift positions, you have parallax. An easy means of correcting parallax without a parallax adjustment is to move your head back slightly until the scope shadow is uniform on all sides of the reticle. This will ensure the eye stays in the correct alignment with the reticle and target, potentially saving valuable target acquisition time while hunting or during a competition shoot.
Lens Coatings and Quality
Riflescopes typically include eight or more lenses, including the objective and ocular lenses. The quality of coatings applied to the lenses directly affects the scope’s overall performance.
The various lenses inside most rifle scopes are coated to reduce glare and reflection, increase the amount of light transmitted, improve true color transmission and protect them from the elements. Except for the quality of the glass used to make a lens, coatings are probably the most important factor in delivering a crisp, clean image of the target.
Light transmission refers to the amount of light that passes through the scope that actually reaches the shooter’s eye. Modern anti-reflection coatings perhaps have done more to improve the quality of today’s scopes than any other single item. Anti-reflective lens coatings are either single or multi-layer. Single layer coatings can increase light transmission by as much as 70%. Multi-layer anti-reflective coatings can improve light transmission by 90% or more.
The other major factors in determining the quality of a scope are the type of glass used in the lenses and the precision with which each is ground, shaped and polished. Inexpensive glass can result in hazy or mirage-distorted images. Even the finest glass, however, won’t result in a high-quality scope if the coatings are inferior or inadequate.
Field of View
A scope’s field of view (FOV) is the lateral area visible to the shooter at 100 yards. FOV decreases with increases in magnification and increases when the magnification power is lowered. Increasing the size of the objective lens has no effect on the field of view.
Larger fields of view offer fast target acquisition, which is why lower powered scopes are normally used when hunting close-range targets in thick underbrush. Speed is normally not a factor when shooting long distances in open terrain, and the lower FOV from a higher magnification isn’t a problem.
Focal Plane
Another feature of today’s riflescopes is the choice of where the reticle is positioned within the scope. The two choices are the first focal plane (FFP) and the second focal plane (SFP).
The majority of today’s scopes use SFP reticles, which means that when the scope’s magnification level is changed, the reticle’s size remains the same in relation to the size of the target. The result is a clear and consistent sight picture at all magnification settings. SFP rifle scopes with BDC or mil dot reticles, however, must be set to maximum magnification to fully utilize their features.
First focal planes do not have this problem. Since the reticle size scales up and down in direct relation to the changes in magnification, the BDC markings and milliradian measurements will be accurate regardless of the scope’s magnification setting. A potential drawback is that at lower levels of magnification such as 3x to 5x, the reticle may be difficult to see clearly, making FFP scopes better suited for long-range shooting, since they will normally be set to higher magnifications.
Reticles
From basic center dots to complex grids, there are literally dozens of reticle patterns available. Here are the three most common reticles in use today:
- Duplex Reticle. The duplex reticle has thin, vertical and horizontal tapered crosshairs that are thicker at the outer edges, which cause the shooter’s eye to focus naturally at the center of the scope’s eyepiece. The crosshair’s thick outer edges help when shooting in low light where the thinner, center crosshairs might not be clearly visible. Duplex reticle scopes are widely used for both target shooting and hunting.
- Mil-dot Reticle. The mil dot reticle is an offshoot of the duplex reticle, which has four tiny, .25 mil diameter dots positioned along each axis arranged to allow for accurately estimating the distance to the target. The mil dot reticle has some significant advantages over the duplex reticle, including the size and spacing of the reticle lines that correspond to specific milliradian angles. The mil-dot reticle can be used to accurately measure the distance to the target, and has the added benefit of allowing the shooter to quickly make intuitive adjustments for windage and elevation. The mil dot’s markings can also be used as a makeshift bullet drop compensator, or BDC, to estimate the amount the projectile will drop over a given distance. The mil dot’s versatility and accuracy have made it the standard reticle for scopes on firearms used by military and law enforcement agency snipers. Because of the mil dot reticle’s intuitive focusing and its ability to allow the shooter to quickly perform distance calculations for windage and elevation adjustments, rifle scopes with mil-dot reticles are recommended for shooting targets at 300 yards or more.
- BDC Reticle. BDC (bullet drop compensator) reticles are more popular today than ever. Utilitarian BDC reticle scopes allow accurate shooting at various distances without adjusting the elevation setting, which is made possible by the aiming points built into the reticle pattern that correspond to different target ranges. A potential drawback to scopes with BDC reticles is that they are compatible only with certain cartridges, such as a .223 with a 55 grain bullet or a .308 cartridge with a 65 grain projectile. BDC reticle scopes are most accurate within 500 yards, and are a great choice for AR-15 rifle platforms.
Rifle Scope Applications and Characteristics
Variable Power Scopes
Not all that long ago, variable power scopes were considered something of a novelty. They were more fragile and less reliable than fixed power telescopic sights, and shifts in point-of-impact were common when magnification settings were increased or decreased. Now, variable power scopes are by far the most popular of all rifle scopes in use today. Variable power rifle scopes are used by hunters, tactical and long-range precision shooters and military and civilian law enforcement agency SWAT teams and snipers.
Hunting Scopes
Just the twist of a knob allows the hunter to immediately change the scope from being set for close-in shooting to taking long range targets. Experienced shooters tend to keep the magnification setting low until a long-range target presents itself, and greater magnification is needed.
For years, 3-9x scopes were preferred by most hunters, and because of its versatility, the 3-9x is still widely used today. The 3x setting is good for most, close-range targets, and a 9-power magnification is enough for most big game hunting ranges. An example of a great 3-9x with a 40mm objective lens that works well for most all-around hunting conditions is the Burris Fullfield E1 or Nikon Monarch scopes. For somewhat longer range shooting situations, such as hunting Bighorn sheep in the mountains or coyotes on the open prairie, a Leupold VX-3i 4.5-14x40mm scope is a great choice.
A 3-18x50mm, such as a Leupold VX-6HD, can extend shooting time. Its large, 50mm objective lens makes it ideal for both intermediate and long distance shooting in early morning or evening low light conditions.
The versatile 4.5-18x can be used for everything from hunting wild boar and other fast-moving game at close to long-range big game hunting. A great example is the Bushnell Elite Long Range Hunter Scope.
Long Range Precision Scopes
Variable power scopes for long range precision shooting (LSRP) come in several power and lens configurations, which are typically from 3-18x up to 7-35x with 50mm to 56mm objective lenses. As the connection between the shooter and the target, a telescopic sight is arguably the most important component of long range precision shooting. The NightForce ATACR 5-25x56mm and Leupold Mark 8 3.5-25x56mm is an example of a rifle scope for long range precision shooting.
Other configurations used for long range precision shooting include the Sig Sauer Tango6 4-24x, Burris 8-40x50mm, Leupold VX-3i LRP 8.5-25x50mm and US Optics 5-25x52mm scopes with 50mm to 56mm objective lenses, all of which and more are available online at Hinterland Outfitters.
Tactical Shooting Rifle Scopes
Tactical rifle shooting requires quick target acquisition at close range, which is why lower-powered variable scopes with 24mm to 40mm objective lenses are usually preferred. Other factors to consider are the distance at which the majority of shooting will take place, the maximum range at which it will be used, the caliber, the weight and length of the rifle and whether the scope will be used in low light shooting conditions.
Popular scope choices for tactical rifles include:
Shopping for a Rifle Scope
Shooters tend to spend a considerable amount of time and energy researching various makes and models before deciding upon their next rifle purchase. Chances are they’ll spend several hundred, if not thousands of dollars on a high-end custom rifle, whether its intended use is for target shooting or hunting. When it comes to selecting a scope for the new rifle, however, the tendency is to quickly grab something inexpensive off the shelf without giving the matter much thought. This is the number one way to degrade your new rifle platform. You wouldn’t use Honda sedan wheels and tires on a Lamborghini would you?
Riflescopes let the shooter see targets more clearly and aim with much greater precision than iron sights. The huge number of options available and the various features of each, however, can be overwhelming to the uninitiated.
One of the first things to consider when shopping for a scope is how it will be used. A bench rest shooter might use a 10x scope for shooting 1,000 yard targets while seated. Hunting game in a forest or thick underbrush, however, would make it difficult to aim accurately through a high-powered telescopic scope, and the hunter would probably find a 3x or 4x scope to be more appropriate. Generally, lower magnifications of 4x to 6x allow the shooter to aim faster and more intuitively. Higher powered scopes of 16x and over offer greater target resolution, but are heavier, more expensive and challenging to use when firing without a bipod, sandbags or other means of support.
Scopes with magnifications of 10x or under are more suitable for firing from the offhand (standing) position or shooting at targets within 500 yards. Rifle scopes over 10x are generally preferred for shooting long distances with a rifle supported by a bipod or other rest.
Although more expensive than fixed magnification scopes, variable rifle scopes provide the best of both worlds, since they offer a wide range of magnifications that can be quickly and easily changed to suit the situation. A potential drawback of variable scopes is that because they contain moving parts, they might be somewhat less rugged than their fixed magnification counterparts. Higher end scopes from reputable manufacturers, however, are unlikely to have durability issues whether they are fixed or variable.
Which Is the “Right” Scope?
Choosing a rifle scope depends in large part upon how it will be mounted and used. Long distance target shooters may need a scope with 12x or higher magnification and precision optical adjustments, whereas a 3x, lower priced scope may be perfectly adequate for hunting in woodlands or heavy brush.
Rifle scopes range in price from less than $50 dollars for a basic, entry level scopes from Tasco, Truglo, Millett or ADCO to thousands of dollars for higher end, precision scopes from, NightForce, US Optics, Swarovski, Schmidt & Bender, Burris or Zeiss. Some other major brands carried by Hinterland Outfitters are Leupold, Bushnell, Millett, Redfield, Sun Optics, Sig Electro, Trijicon and Weaver.
Generally, higher priced scopes offer more precision adjustments, superior clarity, improved accuracy and increased durability. Higher-end scopes may also offer wider choices of reticle types, variable magnification ranges and advanced features including parallax adjustments and illuminated reticles. When in doubt, move up to the next model just to be on the safe side — after all, the scope, like the rifle, can represent a substantial investment, and presumably will be with you for many years to come.
Hinterland Outfitters carries a full line of quality rifle scopes for virtually any shooting situation at prices to fit any budget. After researching our extensive inventory online, contact us by telephone at 877-446-8370 or email us at info@blog.hinterlandoutfitters.com. One of our experienced and knowledgeable team members will be pleased to answer your questions and provide additional information to help you decide which rifle scope is right for your unique situation. You’ll be glad you did.