Telescopic and Red Dot Sights

By Chuck Hawks


For many years I was a camera store manager and professional photographer. Later I became a photography teacher. In the course of pursuing those careers, and because I was interested, I came to have a better than average understanding of optics and lens systems.

I am also an amateur astronomer, and have owned several astronomical telescopes. Being a curious kind of guy, I have done quite a bit of reading about basic telescope designs, the various types of objective and ocular lens designs, and so forth. Conventional telescopic sights are basically small refracting telescopes, so I think I understand some of the trade-off required in their design.

I have tried to present enough information in this article to explain some of the most important aspects of optical sights. I have necessarily left out a great deal of information that might give some readers a better appreciation of the subject, but bore others to tears. I have, for example, not discussed the several types of optical aberrations present in all refracting optical systems, or the design of objective lens systems. This is important stuff, but perhaps a bit beyond the level of understanding most readers wish to achieve. It is sometimes hard to strike the proper balance between brevity and necessary detail.

What I thought would be a fairly short and easy article to write has become a lengthy and somewhat difficult undertaking. As I wrote this piece I kept thinking of issues I should address, and the whole project kept growing in scope and length. For this I apologize, and beg your indulgence.

After decades of reading the popular gun and outdoor magazines, I have become convinced that most gun writers have little real knowledge about optics, although they may know just enough to impress most of their readers. As you will read below, it is much easier for scope companies to sell magnification, which most consumers already understand, than to educate potential customers about the other, often more important, attributes of telescopic sights.

Unfortunately, the reviewers who write the articles about optical sights for the popular magazines may be poorly prepared to inform their readers about the drawbacks of the products they tout. In many cases they seem to be oblivious to the existence of drawbacks! I suspect that many gun writers are inclined to use whatever scope the manufacturer sends them, relying on the information (some might say spin) provided by the manufacturer.

This situation has allowed some counter-productive trends to develop in scope marketing, such as excessive magnification, oversized objective lenses, and the use of intermediate eye relief scopes (so called "scout scopes") on rifles that do not require them. The average hunter should avoid all of these pitfalls, so if what you read below seems a little different from what you have read elsewhere, or excessively detailed, please bear with me.

I guess what I am suggesting is not that you should consider me the ultimate authority on optical sights (for I don't pretend to be), but that you should pick your expert with care. Consider the source of this and any other article on the subject, and make your own decision.

Telescopic sights

The design and manufacture of telescopic sights and mounts has made giant strides since their inception, and particularly since the end of the Second World War. Shooters can now see distant targets clearly, and aim at them precisely.

The optical quality, durability, and precision of scopes have improved dramatically. Adjustments are now almost always internal in hunting scopes, and reticules stay centered. "Duplex" type reticules, a thick crosshair with a fine center cross area invented by Leupold, have virtually replaced the old standard cross hair, as well as the Lee floating dot and the post with cross hair, although these options can sometimes be ordered. Various sorts of range finding reticules are also available.

I prefer the simplest reticules, either a plain medium cross hair or a Duplex cross hair. When the time comes to shoot I want to concentrate on the target, not the miraculous gizmo inside of my scope.

One of the biggest changes has been the emergence, and then the domination, of the variable power scope. Advanced, computer assisted, optical design and multi layer anti-reflection coatings have made this possible. The traditional 2.5x, 2.75x, and 3x scopes have nearly disappeared. They have been supplanted by the 1-3x, 1-4x, and 1.5-6x variable scopes.

The traditional "all-around" 4x scope is still available from most manufacturers, but the 2-7x variable is usually the same physical size, and more versatile. The traditional 6x scope is also still available from several manufacturers for long-range big game rifles and medium range varmint rifles, but the 3-9x variable is more popular. Even on varmint rifles the traditional high fixed power scopes are being supplanted by high power variables of 4-12x and up. There is still a place for the durable, bright, simple, fixed power scope, but the top sellers are the versatile variable power models.

Manufacturing and selling optical sights is a very competitive business, especially since the Japanese makers entered the market. The selection of both telescopic and red dot sights has never been better.

Red dot sights

Electronic "red dot" sights have become increasing popular for handguns. Most of these look like short, fat, long eye relief telescopic sights, but have no magnification. They use battery powered electronics to project a red dot at the point of aim, centered in the optical tube, where the crosshairs of a conventional telescopic sight would appear. Red dot sights usually have conventional turrets with knobs for adjusting the windage and elevation of the sight, again similar to a conventional scope. Some red dot sights have dispensed with the tube altogether, and consist of a base with the optical and electronic systems necessary to project the red dot in a sort of "heads up" display. Most red dot sights come with rings, and mount by clamping to conventional Weaver-style scope bases.

The red dot sight's optics put everything seen through it (red dot and target alike) in the same optical plane, again just like a conventional scope. The long eye relief and zero magnification make it unnecessary to focus a red dot sight.

The intensity (brightness) of the red dot is controlled by a knob, usually in about 10 steps from very dim (for use in near total darkness), to bright enough for use in the brightest full sunlight conditions. The glowing red dot makes a very conspicuous aiming point.

Since small coin sized batteries power red dot sights, it makes sense to keep an extra set handy. They use very little power in operation, and a set of batteries usually lasts at least a couple of years in normal use. You must remember to turn the sight off when the day's shooting is over, however.

Red dot sights have proven in competition to be very fast sights to acquire, and since they have unity magnification, they can be used with both eyes open. They are a boon to pistol shooters, and have also seen use on "slug gun" type shotguns. I have three red dot sights for various pistols, and I like them very much, better than traditional iron sights or a conventional long eye relief scope for most handgun shooting.

Quality

Quality is the most important "feature" of any optical sight. A product that is well made of high quality components is always worth the extra money it costs compared to lower quality (both optically and mechanically) "popular priced" products.

Good quality control alone costs the manufacturer (and you) money. But it is worth the extra investment because the result is a better performing, proven product that should last for decades.

Many things affect both the quality and the price of any optical sight. These include optical considerations like the type of glass and the number of elements selected for lens groups, the design of the eyepieces, the care taken in grinding, polishing, and centering the glass elements, the type and coverage of anti-reflection coatings, the sharpness and contrast of the entire optical system, and how effectively aberrations (always present) are controlled.

Important mechanical considerations include the material the tubes themselves are made of, the construction of the tubes (single or multiple piece), the way the lenses and reticules are mounted and retained in place, the accuracy and repeatability of the windage and elevation adjustment mechanisms, how well the tube is sealed against the elements, the ability of all components to withstand recoil and hard knocks, and the external finish of the sight.

In many cases the brand name is a guide to quality. Companies like Kahles, Leica, Leupold, Nikon, Pentax, Schmitt und Bender, Swarovski, Weaver, and Zeiss have spent decades earning a reputation for high quality optical products, and they are unlikely to produce an inferior product. Other companies, like BSA, Bushnell, Simmons, Swift, and Tasco have built a reputation primarily on low price. Some of these offer extensive lines that include upscale models at higher price points. In general, you usually get what you pay for.

The dealer you buy from also matters. A good sporting goods dealer can help you select the optical sight that best fits your needs. Specialty guns shops and sporting goods stores (the traditional kind that sell guns and fishing tackle, not the kind that sell apparel and shoes) are usually the best sources for both good quality optical sights and good information.

Unfortunately, many sales clerks know virtually nothing about optics, sometimes not even how to focus scopes. Do not buy from a clerk or a store that cannot provide the information you need to make an informed buying decision. Buy where you get the help and information you need. Good service usually costs a little more, but is cheap in the long run.

Magnification (power)

Red dot sights typically have no magnification (they are 1x). Telescopic sights do magnify, and they are commonly described by their magnification (4x, 3-9x, and so on). Sometimes a second number is provided, as in "4x28" or "3-9x36." In this case, the first of these numbers refers to the magnification, and the second is the diameter of the objective (front) lens.

Magnification may be fixed, as in four power (4x), or variable between a low and higher value, as in 3-9x or 4-12x. "4x" means the scope makes whatever you look at appear four times closer than it does to the unaided human eye.

Magnification affects brightness. Other things being equal, the higher the power, the dimmer the view. And magnification also affects the field of view of the scope. Everything being equal, the greater the magnification the smaller the field of view.

Remember that everything is magnified when you look through a telescopic sight, including your own shakes and tremors. (This is particularly apparent with a scoped handgun.) The greater the magnification, the harder it seems to keep the image steady. 2, 3, or 4 power rifle scopes are easier for most people to sight through if the rifle is hand held (not being shot from a rest). The higher power scopes (or higher powered variable scopes) sound like a good deal, but often result in jiggly, blurred views and hard to find targets.

It is easy for manufacturers to sell magnification, and they have no incentive to explain the trade-off required in optical design to increase magnification. Nor do they adequately explain concepts like field of view, depth of field, exit pupil, chromatic aberration, and eye relief, all of which (among other things) are negatively impacted by increasing magnification.

Magnification also affects the physical size and weight of a scope. In general, a scope with more magnification is longer and heavier than a scope with less magnification. So, as you can see, magnification must be balanced against other desirable characteristics when choosing a telescopic sight.

Objective lens (diameter)

The second number most commonly associated with telescopic sights refers to the diameter of the objective (front) lens in millimeters. Thus in "4x32," the "32" means that the front lens of the scope is 32mm in diameter. Note that this is the diameter of the lens itself, not the bell that contains it.

The diameter of the objective is important because it controls how much light the scope can let in, and ultimately transmit to your eye. The bigger the objective, the more "light grasp" the scope has. Read more about this under "Exit pupil." Of course, a large front objective makes for a larger and heavier scope. Which is why compact scopes always have smaller front lenses. A 40mm objective lens is the largest normally required, even for high magnification riflescopes. Low and medium power scopes will do very well with objectives of 20mm to 35mm.

The shape (curvature and design) of the objective lens determines the focal length of the scope, and thus its magnification, and also has a big impact on the scopes definition. These are not functions of its diameter.

Main tube diameter

The standard main tube diameter for most U.S. scopes is 1" (25mm). Early scopes were often built on 3/4" tubes, but these have largely passed from the scene.

A 1" tube is entirely sufficient for North American hunting conditions. It allows sufficient internal windage and elevation adjustment range for all normal purposes. (Unless the mount is really cocked or something like that, which is not the scope's fault.) It also allows the transmission of plenty of light for dawn to dusk hunting. Scopes with 1" tubes are lighter than scopes with 30mm tubes, which is always an advantage.

Many premium European scopes come with slightly larger 30mm main tubes, and some North American manufacturers have followed suit for their top of the line models in order to "keep up" with the Europeans. The Leupold LPS and Sightron SIII would be examples of scopes with 30mm main tubes. The rationale behind the larger main tube is primarily more efficient internal light transmission. These scopes are also usually equipped with "syrup bucket" objective bells. This is because in much of Europe, unlike North America, night time hunting is legal and widely practiced. Big scopes negatively impact the handling qualities of the rifle and should be avoided unless they are really necessary.

Choose a scope with a 25mm main tube for all North America hunting conditions and general purpose use anywhere in the world. Consider a scope with a 30mm tube only if the rifle is being set-up specifically for hunting in full darkness.

Clear aperture

The clear aperture of a scope should be the same as the diameter of the objective lens. Clear aperture refers to how much light can actually enter the scopes optical system. It is the diameter of the objective lens less any other obstruction that reduces the amount of light transmitted by the system (secondary mirrors, internal baffles, mounting rings, etc).

Clear aperture is actually the measurement that should be used to calculate the exit pupil, and upon which the light grasp of the scope depends. Some poorly designed scopes may have a clear aperture smaller than the size of their front lens. Clear aperture is seldom discussed by optical sight manufacturers, only objective lens diameter, so once again a top quality brand name is probably your best assurance that you are actually getting what you paid for.

Light transmission

Light transmission affects how much light makes it through the lenses inside of a scope and out to your eye. It is influenced by the type and quality of the glasses used, the anti-reflection coatings, and the control of glare inside the scope. It is a hard thing to prove (or disprove), and recently some scope companies have been making some pretty wild claims about their scope's light transmission.

Exit pupil

The magnification and the clear aperture (usually the diameter of the objective lens) of a scope determines the size of the exit pupil. The size of the exit pupil determines how much light is transmitted to your eye. The exit pupil can be seen by holding the scope at arm's length and looking through the eyepiece. The pencil of light you see is the exit pupil.

The diameter of the exit pupil is easily computed. Divide the diameter of the front objective lens (in millimeters) by the magnification of the scope. For example, take a typical 4 power rifle scope with a 32mm objective lens. Divide 32 (the diameter of the objective) by 4 (the magnification) and you get 8. 8mm is the diameter of the exit pupil for a 4x32 scope.

Now let's figure the exit pupil of a 12x40 scope (or a 4-12x variable power scope with a 40mm front objective set to 12x). Divide 40 by 12 and you get 3.33. So the exit pupil is 3.33mm. A lot less light potentially reaches your eye from a 12x40 scope than does from a 4x32 scope.

Why does the diameter of the exit pupil matter? It doesn't, as long as there is enough ambient light so that the pupil of your eye is smaller than the exit pupil of your scope. But when the ambient light gets dim, and the pupils of your eyes adapt by enlarging, the exit pupil of your scope may become the limiting factor. With the 12x40 rifle scope in the example above, when it gets dim enough for the pupils of your eyes to exceed 3.33mm in diameter, the scope is restricting the light available to your eyes.

Ideally, human eyes in excellent condition can achieve about a 7mm pupil opening, so a 3.33mm exit pupil can be quite limiting in dim light. You may be able to see more when you are not looking through your scope. But the 4x32 scope in the first example above has an 8mm exit pupil, larger than young, fully dark adapted human eyes can achieve, so it never limits what you can see, even at night.

The human eye loses its ability to adapt to dim light as it ages, so a middle-aged person's maximum pupil size is typically down to around 5mm. Elderly eyes are often limited to about a 4mm maximum pupil diameter. So as we age, the exit pupil size we need decreases.

Field of view

The field of view is the area seen through your optical sight. It is properly measured in degrees, but for catalog purposes most scope manufacturers state how much linear area is encompassed by their scope's field of view at a certain range (usually in feet at 100 yards or meters at 100 meters). In any case, the larger the field of view the more area you can see through your scope. A big field of view is particularly important at close range, or for following moving animals.

Since field of view is measured in degrees, the closer the shooter is to the target, the smaller the actual area he sees through his scope. Field of view is inversely proportional to magnification. For these reasons, the woods hunter or someone who may have to shoot at running game needs a lower power scope because it provides a bigger field of view. For example, a Leupold Vari-X II 3-9x variable power scope has a linear field of 32.3 feet at 100 yards when set at 3x, but only 14.0 feet at 9x.

If you use a variable power scope, keep it set at low magnification for maximum field of view when you are out hunting. If you leave your scope at high power and jump a deer at close range, it is pretty frustrating to see only a patch of hide when you snap your rifle to your shoulder, and have no idea what part of the deer you are looking at. This has happened many times to many hunters. I always leave my variable power scopes on low power until I actually need to turn the magnification up to make a shot.

Eye relief

The term "eye relief" refers to the distance from the scope's ocular lens to the eye. For .22 rifles it can be as little as 1.5 inches, since recoil is not a problem. Short eye relief is common for rimfire scopes. Scopes with short eye relief should never be used on centerfire rifles.

For most centerfire rifle calibers 3 to 5 inches is about right. I prefer a scope with about 4 inches of eye relief. This longer eye relief is necessary to keep the scope from hitting the shooter's eyebrow when the rifle recoils. Pay particular attention to the eye relief specification when buying a scope for a magnum rifle. High magnification scopes tend to have less eye relief, as do variable power scopes. Economy scopes also tend to scrimp on eye relief.

Handgun scopes are normally fired at arm's length, and require a scope with extra long eye relief (in excess of 20 inches). Extended eye relief (EER) dramatically reduces the field of view seen through the scope--another optical trade off. In optics there is no free lunch. Which is why the fad for using "tactical" scopes with longer than normal eye relief on rifles that normally don't require an extended eye relief scope doesn't really make a lot of sense.

I have some experience with this, as back in 1966 I had a custom mount made to mount a 2x Leupold EER scope forward of the receiver on my Winchester 1866 Centennial rifle (a commemorative version of the Model 94). That rifle ejected straight up and could not accept a scope mounted over the receiver. The bottom line to the story is that while it was much better than no scope at all, I found no advantage to the EER scope, and it did have the major disadvantage of a greatly reduced field of view. I tried to solve the problem by shooting with both eyes open, looking simultaneously around and through the scope. While this technique works pretty well with a zero magnification red dot sight used at arm's length on a handgun, it is much less effective with a scope that magnifies the target mounted at an intermediate distance on a rifle. I would avoid modern "tactical" scopes like the plague on any rifle that didn't really require one.

Where EER scopes are really necessary is on handguns. I have used scopes on handguns since the very first scope for the purpose (the Bushnell Phantom) became available in the middle 1960's. Optical sights put the target and the point of aim into the same optical plane. This is a great advantage to accurate pistol shooting, particularly at ranges greater than about 25 yards.

Contrast and resolution

These are probably the most easily recognized optical properties of any scope. Resolution essentially means sharpness, a scope with good resolution can resolve fine details. Contrast means crispness, snap, the ability to separate one thing from another. (For a dramatic illustration of the importance of contrast, play with the contrast control on your computer monitor or TV set.) Together, they primarily determine how clear things look through a scope. Good design, premium quality optics, good lens coatings, good internal flare suppression, precise assembly, and good quality control usually result in a scope with high resolution and contrast. Unfortunately, none of these things are cheap.

Parallax

The American Heritage Dictionary defines "parallax" as: "An apparent change in the direction of an object, caused by a change in observational position that provides a new line of sight."

In a discussion of optical sights the word usually refers to the apparent movement of the target relative to the reticle (or red dot) when you move your head as you look through the scope. For technical reasons, parallax can only be eliminated from an optical sight at one range, although it is not usually apparent in normal use unless there is something wrong with the sight. Leupold, for example, designs their centerfire rifle scopes to be parallax free at 150 yards; rimfire rifle and shotgun scopes are designed to be parallax free at 75 yards. Some special telescopic sights, usually long range varmint or target models, come with an adjustable objective that can be adjusted to eliminate parallax at specific distances.

There is another way the word parallax applies to guns and sights. The line of sight is different than the axis of the bore, because the sight is mounted above the bore. This distance between the line of sight and the center of the bore (about 1.5 inches for a low mounted scope) creates parallax (see definition above). To minimize the effect of parallax, always mount an optical sight as close to the bore as possible.

Lens coatings

Most optical sights have magnesium-fluoride anti-reflection coatings on their air to glass surfaces. These coatings assist light transmission. They are what produce the blue, red, or green reflections you see when you look into the front (objective) lens of a scope or red dot sight.

But note how the manufacturer describes his anti-reflection lens coatings. "Coated" means a single layer anti-reflection coating on some lens elements, usually the first and last elements--the only ones you can see. "Fully Coated" means that all air to glass surfaces are coated. This is good. "Multi-Coated" means that at least some surfaces (again, usually the first and the last) have multiple layers of anti-reflection coatings. (The others may have single layer coatings, or none at all.) "Fully Multi-Coated" means that all air to glass surfaces have received multiple layers of anti-reflection coatings. Multiple coating layers are somewhat more effective than a single layer. Always buy Fully Coated or Fully Multi-Coated optical sights. Both are perfectly satisfactory.

A couple of new wrinkles in lens coatings are Leupold's DiamondCoat and Bushnell's Rainguard. The former is an extremely hard ion-assist protective coating applied to the outside elements of the objective and ocular lenses. It is highly resistant to scratching and abrasion and is currently being applied to Leupold's LPS and VX-L series riflescopes and the Mark 4 CQ/T scope adopted by the U.S. military.

Bushnell's Rainguard, applied to the front and rear outside elements of Elite series riflescopes, is a hydrophobic coating that breaks-up and sheds water drops to reduce the glare they cause. It works in snow, rain and fog and is of real benefit to those who hunt in inclement weather. Leupold, Simmons and others have copied this technology and introduced similar coatings under different names (RainCote, HydroShield, etc.).

Focusing a telescopic sight

It is surprising how many people do not know how to focus their rifle scopes. The idea is to focus on the reticule (crosshair), not some object in the distance. To focus a scope, set it to its highest useable power and go outside. Point the scope at a blank area of sky. Turn the ocular bell housing (the end closest to your eye) until the reticule appears to be perfectly sharp. Tighten the locking ring and your scope is focused to your eye. You will not have to change it unless your vision changes.

Fixed magnification scopes

Fixed magnification scopes of 2, 2.5, 2.75, 3, 4, 6, 8, and 10 power used to be common for hunting purposes. The scopes with magnifications of 3x and less were considered ideal for woods hunting, where a wide field of view is more important than magnification. Today, low power rifle scopes are pretty hard to find; they have been largely replaced by variable power scopes in the 1-4x range.

The 4x scope was considered to be the standard "all-around" hunting scope for both rimfire and big game hunting rifles. The 4x scope is still popular and widely available. It has a reasonable field of view for general purpose use. It will allow accurate shot placement on big game animals to at least 300 yards, and riflemen who can shoot well enough to consistently kill a deer size with one shot beyond that range are few and far between, regardless of what you read in the hunting and gun magazines. A quality 4x scope remains a good choice for an "all-around" rifle.

Likewise, 4x is about all the magnification the small game hunter with a .22 rimfire rifle can use. Years ago I did some field research and concluded that 3x offered an excellent balance of magnification and field of view for a .22 rifle. But 3x scopes for .22 rifles are unavailable today, while 4x models are common and just about as useful.

Fixed magnification scopes still have important advantages when compared to variable power models. In scopes of the same quality and maximum magnification, a fixed power scope is optically superior. It is also simpler in design and construction, and therefore more durable. The fixed power scope is easier to seal against water and dust. It is usually lighter and more compact than a variable power scope. And fixed power scopes are less expensive than equivalent quality variable power scopes. For all of these reasons a fixed power scope may be a better choice than a variable power scope, depending on the application.

The fixed power scope has evolved from being the only choice, to being the choice of hunters more interested in economy than versatility (i.e. who couldn't afford a variable power scope), to being the choice of discerning and knowledgeable shooters.

Variable power scopes

The great advantage of variable power (zoom) scopes is the freedom they give the shooter to select a larger field of view or greater magnification, depending on the situation. This is an enormous asset on a dual purpose rifle, or an all-around rifle. The rifleman who shoots only at close range, or who always shoots at long range, has no real need for a variable power scope. But hunters who may hunt mule deer in the mountains, where shots across canyons are common, and Roosevelt elk in deep cover with the same rifle will find a variable power scope a great asset. For them a 2-7x variable scope is pretty hard to beat.

The hunter who uses his or her 6mm rifle for varmint shooting during the off season and deer and antelope hunting in the fall will find a 3-9x, or 2.5-10x variable power scope a boon. It is much easier to turn a ring to change the magnification and field of view of a variable power scope than to dismount and re-mount (and re-zero) a pair of fixed power scopes, and more economical to boot.

Because of this the 3-9x variable scope has replaced the fixed 4x scope as the best selling optical sight for rifles. Actually, the more compact 2-7x scope is probably a better all-around choice, but consumers have been pretty well brainwashed in favor of higher magnification.

Variable power (zoom) scopes almost always perform better at the low to medium power settings than they do at the highest settings. Most of them have an optical "sweet spot" that can be determined by careful observation. For example, in a 2-7x variable this often occurs around 3-4x, or in a 3-9x scope this often occurs around 4-5x. This is natural, since the entire design of a variable power scope is a series of compromises--a zoom scope cannot be optimized for any one magnification and field of view, since it must be satisfactory over a wide range. And the wider the zoom range, the greater the optical compromises that must be made. Always buy the narrowest zoom range you can get by with. Don't go for a 2.5-10x scope if a 3-9x model will do the job. You are not getting "extra power" for your money; you are getting a more compromised optical design.

Since the front objective of a variable power telescopic sight cannot enlarge to let in more light as the magnification is increased, the view gets dimmer as the magnification goes up. This is because the exit pupil gets smaller. (See the section on exit pupil for more on this subject.)

Mounts and rings

No matter how good an optical sight may be, if it is not mounted securely and immovably to the gun it is not going to be much use as a sighting instrument. Red dot sights usually come with rings that attach to a Weaver-style base, and some handguns even have barrel ribs that are the equivalent of a built in Weaver base.

Handguns intended for hunting occasionally come with rings for conventional scopes and have the mounting points for them machined into the frame or barrel rib. The Ruger Super Blackhawk Hunter is an example of such a handgun.

Most conventional pistol scopes accept standard 25mm (1") rings that mount to a conventional base. Leupold offers bases and rings for many popular handguns, and Weaver offers bases and rings for nearly all handguns adaptable to a scope, so mounting a red dot sight or pistol scope is usually not much of a problem.

I once had a red dot sight (a Tasco PDP-4) that had so little longitudinal adjustment for its rings that it would not mount on the revolver for which I had purchased it. I tried to mount that sight on three different pistols before I found one that would accommodate its ring spacing, and that one already wore a red dot sight! That experience taught me to compare a red dot sight's ring spacing and the mount it is intended to fit in the store, before purchasing either.

The same sort of problem can occur with a conventional rifle or pistol scope if they have relatively short tubes and large bell housings and adjustment turrets. That also happened to me once. Usually there is no problem, however, as conventional scopes have much longer tubes than red dot sights.

Most of the scope manufacturers offer mounts and rings for their scopes, and there are companies that only supply mounts and rings. Most telescopic sights have 25mm (1") diameter tubes, and standard rings are designed to accept scope tubes of this diameter. Some scopes have larger 30mm diameter tubes, and rings that attach to standard bases are also available in this size.

Rings come in various heights, usually low, medium, and high. Always use the lowest rings that will allow the bell housing at the front of the scope to clear the gun's barrel. A scope should ideally be mounted directly over the bore and as low as possible to minimize parallax.

Because they increase parallax, high "see through" scope mounts designed to let the hunter use a rifle's iron sights without removing the scope are a bad idea. They also force the shooter to shoot with his head up, reducing contact with the comb of the stock and degrading practical accuracy.

A proper scope is faster and more accurate than any iron sight. There is simply no need for the latter except in an emergency involving damage to the scope. In case of that unlikely event, it is no problem to keep a screwdriver or Allen wrench in camp to remove a damaged scope. For the same reasons, plus their added complexity and reduced rigidity, "swing away" scope mounts that allow a scope to be rotated to the side to clear iron sights should also be avoided.

Bases for rifles generally come in one piece or two piece styles, depending on the action they are intended to fit. Many actions can accept either type, so the shooter has to make a choice. I always use a one piece base if possible. I believe they are stronger and less subject to miss-alignment. You must always buy a base intended for the type of rings you intend to use, a Weaver-type base for Weaver type rings, or a Redfield-type base for Redfield-type rings.

Leupold bases and rings are identical to Redfield bases and rings, and the two are interchangeable. I have heard that Burris also copied the basic Redfield design and that their rings and bases are interchangeable with the first two. Burris offers an interesting "ring within a ring" that mounts to Redfield/Leupold-type bases.

Several companies have also copied the Weaver bases and rings, and their rings and bases should interchange with Weaver bases and rings. The Tasco supplied rings I have used on pistol sights, for instance, mate perfectly to Weaver bases.

Most scope bases are designed to accept either the Redfield/Leupold-type rings or the Weaver-type rings. Although I have found Weaver rings and bases to be completely satisfactory, I prefer the Redfield/Leupold rings for two main reasons. First, they are locked-on to the base rather than clamped over it. And second, they are machined rings that come in halves. This means that you mount the lower half of each ring to the rifle and set the scope in the lower ring halves in whatever position you want it. Then place the top half of each ring over the scope tube, and use the supplied screws to attach the upper half of each ring to the lower half, clamping the scope in place. The scope does not move at all as you tighten the screws.

The standard Redfield/Leupold bases also have another advantage. The way the rear ring is secured to the base allows for windage adjustment when you bore-sight your rifle, so you can get the scope perfectly aligned (left to right) with the rifle barrel without touching the windage adjustment of the scope itself. Naturally, the rear ring must be fully tightened before you begin actual shooting.

Weaver type rings are more complicated. They are also a two piece design. The rings are fabricated from two pieces of heavy gauge sheet steel rather than machined. The two parts of each ring hook together on one side, and are clamped together by two screws on the other side. They don't seem to fit the scope tube as perfectly as the machined Redfield-type rings, and as they are tightened from only one side the scope rotates slightly as the screws pull the rings tight. To get the crosshairs straight you must allow for this rotation of the scope tube during tightening. I have gotten fairly good at it, but it is a learned process and can be quite frustrating.

Optical sights for pistols

Optical sights for pistols require very long eye relief, because the handgun is typically held at arm's length. This requires special optical design and results in a reduced field of view.

Telescopic sights for pistols are typically of low magnification for several good reasons. Among these is the relatively short range of traditional straight walled pistol cartridges, which makes high magnification unnecessary. Also, the movement (jiggle) normally associated with holding a pistol at arms length becomes very annoying when magnified several times. Most handguns, even magnum revolvers, are small compared to rifles and a large scope makes them feel very top heavy.

Most handgun hunters favor a 1.5x or 2x fixed power scope, or a 1-4x variable scope. These provide a reasonable field of view and minimize jiggle blur.

For varmint hunting with specialty pistols, higher power scopes are in vogue, commensurate with the flat trajectory and extended range of the rifle cartridges these pistols use. A fixed 4x or 6x scope, or a variable 2.5-8x long eye relief scope would seem to be the answer.

Perhaps the best sort of optical sight for most pistol applications is the red dot sight. Its zero magnification minimizes the annoyance of the unavoidable gun tremor inherent in pistol shooting, and increases the field of view. The fat tube diameter of most red dot sights (over 30mm) also increases field of view. The bright red, glowing, aiming point is easier to acquire than a conventional black crosshair, even if the gun is not held perfectly in line with the eye. And the glowing red dot can be seen in any lighting condition, including full darkness--an important consideration for a hunting pistol also used for home defense.

Scopes for hunting rifles

For seeing targets in dim light, you need fairly bright optics. For example, the navies of the world generally use 7x50 binoculars (7x with a 50mm objective) on their ships. These offer a 7.1mm exit pupil, and gather all the light young eyes can use, even at night. But such binoculars are comparatively heavy and bulky, and so is a rifle scope with a 50mm objective. The big game hunter seldom needs 7x magnification and is usually better served by something more compact. And, in any case, hunting at night is illegal in most jurisdictions.

For hunting applications a 5mm exit pupil is usually quite satisfactory. A 5mm exit pupil is bright enough to allow the observer to see into shadowed areas, or in very dim light, and the scope can be made compact enough to not be an excessive burden on the rifle.

This means that a 2.5x fixed power scope really only requires a 12.5mm clear aperture. A 2.5x scope with a straight tube and a 20mm objective (which is common for that power) actually has an 8mm exit pupil.

A 1-4x variable needs only a 20mm objective at maximum power for a 5mm exit pupil. Set that scope to 2.85x and you have a 7mm exit pupil for shooting in the dead of night (assuming your eyes are perfect and can actually make use of that big an exit pupil).

A fixed 4x scope with a 32mm objective has an 8mm exit pupil, which will give even a fully dark adapted eye more light than it can use. The same applies to a variable power scope with a 32mm objective, like a 2-7x, when set at 4x.

A scope set at 8x requires a 40mm objective for a 5mm exit pupil. It is hard to imagine needing more magnification or light grasp than that for shooting big game. The same 40mm objective will give a 7mm exit pupil at 5.7x. What more could a hunter ask for? Rifle scopes are sights, not instruments for astronomical observation.

Objective lenses larger than 40mm tend to make for heavy and bulky scopes that are unsightly as well as a burden to carry. Unless one really needs the high power and extra light grasp they are better avoided. The proliferation of scopes with very large objectives indicates that there must be a market for them, but I have to believe it is composed largely of shooters who are not well informed about optics and have been sucked in by advertising spin.

Scopes for big game rifles

Field of view is the most important requirement for a scope that is likely to be used at fairly close range. The woods hunter will be well served by a telescopic sight with a generous field of view, like a 1-4x variable or a 2x to 3x fixed power rifle scope.

The common 4x fixed power scope or a 2-7x variable is probably about as good as anything for general purpose field use. Such scopes are particularly appropriate on "all-around" rifles in calibers like .270, .308, and .30-06.Varmint shooters can and do use high magnification scopes. Variable power scopes of 4-12x and greater power are the most popular type for long range varmint rifles.

The mountain or plains hunter is likely to take more shots at longer ranges than other big game hunters. But not all shots will be long, and some may be quite close. For the long range big game rifle a 3-9x variable scope is just about ideal. It offers a reasonable field of view at 3x, and at 6x to 9x all the magnification a big game hunter will ever need for even the longest shots.

A rifle intended for use on dangerous game should never be equipped with a high magnification scope. All dangerous game animals are fairly large, and shots at dangerous game beyond 200 yards are generally frowned upon. A large field of view is crucially important for fast target acquisition at the ranges at which dangerous animals are typically engaged. A fixed 2x or 2.5x scope is about right, or a 1-3x or 1-4x variable.

High magnification variable scopes can lead to tragedy in the presence of dangerous game. Should the hunter actually use the high magnification to look or shoot at something at long range, and forget to reset the scope to low magnification, the reduced field of view at the higher power could be fatal in the event of a subsequent unexpected charge.

Scopes for varmint rifles

The varmint hunter needs a high power scope for his or her rifle, since the range is likely to be long and the target small. Most shooting will be at static targets from a steady position or a rest, and a large field of view is not usually necessary. Varmint rifles are themselves heavy, and they are ordinarily not carried long distances.

Fixed power scopes of from 8x to 20x are fairly common on varmint rifles chambered for cartridges like the .22-250 and 6mm Remington. High powered variable scopes are the most popular type. Scopes like the Leupold 4-12x40mm Vari-X II or 6-18x40mm Vari-X III with adjustable objective typify the modern varmint scope.

Scopes for .22 rimfire rifles

A good scope is a practical necessity for consistent, humane kills. It is also a great asset when plinking at tiny targets. A compact fixed power scope of 3 or 4 power is about right, and all that is needed. A compact variable like a 3-6x is plenty of scope for a .22 hunting or plinking rifle. A high power or variable scope with a large objective is too heavy and bulky, and is a poor choice for a .22 rifle. Most .22's have receivers that are grooved for "tip-off" scope mounts. A few require standard type bases and rings, similar to those used for centerfire hunting rifles. Either system is suitable for a .22, because recoil is not a factor.

A scope designed for a .22 rifle need not have the comparatively long (3 inches or more) eye relief necessary for a hard kicking high power rifle. The slight recoil from the .22 Long Rifle cartridge will not drive a scope back into the shooter's eye. So a 1.5 inch eye relief is adequate. And the internal construction of the scope does not need to be designed to withstand the acceleration caused by the recoil of a high powered rifle. This makes a scope designed specifically for a .22 rifle less expensive than a scope designed for centerfire rifles.

.22 scopes are designed to be parallax free at a shorter distance (usually 75 yards) than scopes designed for centerfire rifles, since they will be used for small targets at comparatively short range, instead of large targets at long range. A good .22 scope does need to have accurate internal adjustments and high quality optics.

While most scopes for high power rifles can be adapted to a .22, some scope manufacturers offer models designed specifically for .22 rimfire rifles. Burris, Bushnell, Leupold, Simmons, Tasco, and Weaver are among the popular brands that offer such scopes. Redfield used to make an excellent compact 4x scope suitable for .22 rifles, and perhaps will again. I have used this, as well as Weaver 4x fixed and 3-6x variable power .22 scopes to take a lot of small game.

Shotgun Scopes

Shotguns firing rifled slugs ("slug guns") are required for deer hunting in some eastern states. Several manufacturers offer scopes specifically intended for use on slug guns. Often these are cheaper than similar rifle scopes. The hunter forced by regulation to use a shotgun with slugs for deer hunting will be well served by the shotgun version of the same sort of scope used by the woods rifleman. A fixed 2.5x shotgun scope, or a 1-4x or 1.5-5x variable power shotgun scope, would seem to be good bets.

Shotgun scopes tend to have somewhat longer eye relief than rifle scopes of similar power, around 5 inches, perhaps because most shotguns firing rifled slugs kick like the devil. Shotgun scopes are (or should be) parallax free at 75 yards rather than 150 yards like most rifle scopes. And some shotgun scopes come with a heavier reticule appropriate for close range shooting in dense cover.

Some shotgun scopes are mounted on the slug barrel of a standard pump or autoloading shotgun. This allows a shotgun used for bird hunting most of the year to become a slug gun during deer season by simply swapping barrels. For this purpose an extended eye relief scope like the M8 2x Leupold would seem to be a good choice. Another good choice would be a quality red dot sight mounted in the same location.

Recommended brands

I cannot comment on all of the brands on the market today, but I will mention those brands with whose optics I have had some experience. (For more recommendations, see my article "Recommended Riflescopes," which can be found on the Scopes and Sport Optics Page.) In the travel industry (remember, I also have a Travel site on the web) hotels and cruise lines are commonly given star ratings, from one star (*) to a maximum of five stars (*****). One star would represent a very low priced and probably unsatisfactory product; two stars represent the economy class product; three stars represent the standard or medium price and quality product; four stars represent a deluxe, high priced product; five stars represent an ultra-deluxe, very high end product. Sometimes a plus (+) is awarded to a product at the top of its class.

In order to compare "apples to apples" (so to speak), I am going to adopt a similar system here for my comments about specific brands of optical sights. It would hardly be fair, for example, to compare a perfectly satisfactory and well made Weaver scope costing $300 to a $1500+ Swarovski scope whose one-piece 30mm tube is machined from a solid block of aircraft grade aluminum alloy. (Yes, it is!)

ONE-STAR

These are typically the blister pack scopes you see at discount department stores. Brands such as BSA, Tasco and "house brand" scopes. Basically, they are not worth purchasing or discussing.

TWO-STAR

What I think of as the economy scope lines include such brands as Swift, the lower end of the Bushnell line and Simmons. Frankly, I learned long ago that buying cheap is expensive in the long run. Among the two-star brands I usually recommend Bushnell, who has successfully marketed low priced scopes for decades.

The Bushnell Banner and Trophy lines are worth considering when low price is the primary consideration. Bushnell scopes have generally provided satisfactory performance and the company has earned a reputation for standing behind its products. The Bushnell sales representatives I have met have been knowledgable and helpful. The Bushnell line encompasses a very wide range of optical sights at an equally wide range of prices, from economy models on up into the deluxe price range.

Less well known to most consumers is the name Mueller. Mueller Extreme Sports Optics markets the two-star-plus Eraticator riflescope. This is a high power varmint scope with excellent features for its moderate price, including fully multi-coated optics, target type adjustment turrets with 1/8 MOA clicks, an illuminated reticle, European style fast focus eyepiece and more.

Very strong contenders in the two-star-plus category are the new Redfield line (made by Leupold) and the Sightron Series One (SI). These are unusually well made scopes for the price.

THREE-STAR

Bill Weaver was one of the pioneers of telescopic sights, and introduced the first popularly priced scope to the American market long before the Second World War. Weaver is now owned by the Meade Telescope Company. Today the mainstays of the Weaver riflescope line are the variable power V-series and fixed power K-series. Weaver .22 rifle scopes, handgun scopes, and red dot sights have also proven reliable and durable. In addition, the people at Weaver have always been exceptionally helpful when I had questions. I have been using Weaver scopes since the K4 came in a blued steel tube and lacked coated optics. For years Weaver scopes have been my first choice among the medium price brands. Weaver also makes a very extensive line of scope mounts. The Weaver mounting system has been widely copied by other manufacturers, and is as close to a standard as we have.

Leupold & Stevens was founded in 1947. Leupold scopes are made in the U.S.A. in Beaverton, Oregon. They are so well known and highly regarded that there is not much I can say that has not been said before. They are the favored brand of professional guides, outdoor writers, competitive shooters, and custom rifle builders all over North America. They have also been chosen for use by elite U.S. military forces. Leupold invented the Duplex reticule, which has been copied by virtually every other scope manufacturer in the world. Leupold scope lines now cover the middle to premium price classes (three-star to five-star). In the three-star class Leupold offers the FX-I and VX-I lines.

I have owned and reviewed a VX-I and found it to be roughly comparable to a Weaver V-series scope. Also roughly comparable is the Nikon Buckmaster line. All are servicable scopes.

THREE-STAR-PLUS

The Bushnell Elite 3200 series has an excellent reputation in the medium price class. Randy Wakeman, Guns and Shooting Online Senior Contributing Editor, has written very complimentary things about these scopes, and so have I. I regard the Elite 3200s as being at the top of the three-star category and generally the best buy in their price class. (For more on rifle scope price classes, see the article "Riflescopes by Price Class" on the Scopes and Sport Optics Page.)

The new Weaver Classic Extreme line features 30mm main tubes and other features that put them near the four-star class. These excellent scope are at the very top of the three-star cartgory.

FOUR-STAR

Weaver has entered the four-star arena with their excellent and rugged Grand Slam and Super Slam lines. In price they are roughly comparable to the Leupold VX-II and Sightron SII / SIIB scopes. Grand Slam scopes are made in Japan and have excellent features including camera quality optics, one piece tubes, "European" style fast focusing, accurate click adjustments and an easy to manipulate "sure grip" variable power ring. The Weaver Grand Slam scopes are a best buy in the medium-high price class.

My favorite Leupold scopes are the VX-II and VX-III series variable power models. These are quality products both optically and mechanically, and are worth every penny of their price. At the top of the four-star category are the Leupold VX-L scopes, notable for their big objectives and low mounting capability. The VX-L's are sort of super VX-III's. All Leupold scopes are covered by their famous Lifetime Guarantee, which applies to all Leupold scopes even if the scope was purchased used--no warrantee card needed. Leupold's customer service is simply the best. Leupold also produces an extensive line of excellent scope mounts of the Redfield and, more recently, Weaver type. Both the VX-II and VX-III lines have earned best buy status in their respective price classes.

Sightron, founded in 1994, is a relative newcomer to the optics business. I have gained considerable experience with their extensive Series Two (SII) Big Sky scope line, which I would judge as about equal (and similar in price) to the Leupold VX-II line. Sightron scopes are made in Japan and combine good optics, precise adjustments, a lifetime warrantee (to any owner, not just the original purchaser), and an attractive finish at a price that makes them an excellent value. Sightron also offers the more expensive SIII scope line, built on 30mm tubes and intended to compete with other upscale (four-star-plus) scopes, as well as red dot electronic sights. Sightron seems to be a well run outfit, responsive to the needs of its customers. The have earned a reputation for very good customer service and the SII Big Sky line is definitely a best buy in the medium price class.

Like about 90% of all professional photographers, I have used Nikon cameras and lenses for a long time. I was what Nikon used to call an Advanced Systems Specialist when I was in the retail end of the photography business. I have a long history with Nikon optical products and a lot of respect for the company itself and the professional way they work with both their dealers and customers. When they introduced their line of Monarch scopes I was not surprised to find that they were solidly in the four-star class. Before long I was using Nikon scopes myself.

Zeiss has successfully entered the four-star arena with their Conquest line of hunting scopes. These scopes are assembled in America and have earned a good reputation. They feature, among other things, a Lifetime Transferable Warranty and the prestige of their famous German name.

The German made Docter Sport Optic line competes with the upper price range of four-star scopes. These are solid, high quality scopes in the European tradition and less expensive than the bulk of the Swarovski, Kahles and Zeiss lines. If you prefer German optics, take a look at the Docter Sport Optic line.

The Bushnell Elite 4200 series is well up in the four-star price class. Like other Bushnell Elite products, these are excellent value for the money.

FIVE-STAR

This is the price range of the ultra-deluxe rifle scopes from Leupold (VX-6), Kahles (Helia line), Schmidt & Bender, Swarovski and Zeiss (Diavari line). The European scopes offer features best suited to European, rather than North American, hunting practices, but offer excellent optical and mechanical quality. (The Leupold VX-6 line is the exception here.) This makes most European models heavy and bulky, with oversize (30mm) tubes and syrup-bucket objective lenses, as it is legal to hunt at night in many parts of Europe.

Leupold offers their ultra-deluxe VX-6 line in direct competition with the best European scopes. These feature one-piece 30mm tubes, big objective lenses, special lens coatings, 4" constant eye relief and European fast focusing, among other desirable features. All Leupold riflescopes, including the VX-6 series, are made in the U.S.A. So far they seem to be holding their own. I would tend to favor a Leupold VX-6 if I were shopping for another five-star scope, as they are designed and built in the US for North American hunters.

Incredible care goes into the manufacture of all of these exquisite five-star scopes, probably beyond what is necessary, or even reasonable. Of course, that is the way it is with products that are the absolute best of their type.

Conclusion

Over spend, but don't over buy. This contradictory sounding advice is actually pretty good. What I mean is, buy the very best quality optical sight you can afford, even if you have to scrimp to do it. However, don't buy more magnification, light grasp (objective size), weight and bulk than you actually need. Spend big bucks, but take a minimalist approach. The same applies to mounts. Avoid gimmicks and complexity; spend your money on solid, low height, quality mounts. Whatever magnification or type of optical sight best fits your needs, if you buy top quality sights and mounts you will not be disappointed.




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