Application



The history of "red dot" sights goes back many decades. They were originally developed for the American sporting market. American special forces units then began buying them in the civilian market for use in low-light raids, allowing them to increase their shooting effectiveness by orders of magnitude, saving many lives. So it has been with many technologies that are now used extensively by our military (Second Amendment supporters take note - does "...the security of a Free State.." ring a bell?). Development for profit in the free market occurs at zero cost to the taxpayer and often in advance of any perceived need.



Anytime you would use iron sights, and at the same distances, you can use electronic sights. The electronic sights will be a lot faster on target, easier to use in a wider range of lighting conditions, and you'll keep your natural view of the target and its surroundings in the process. They are for high speed, at close to medium range, and are particularly superior for engaging a moving target. This makes them equally desirable for self defense, military, hunting, plinking, competition, and law enforcement.



While electronic sights are often called "red dot sights" the aiming reticle is not always red, and it's not always a simple dot. Most electronic sights have no optical magnification, but there are some 2x versions now offered. At least two companies-- Aimpoint and EOTech, now produce a 3x and 4x magnifier, which is a separate optic with no reticle, designed to mount behind your 1x sight and convert it for use as a medium to long range sight. It offers quick conversion from 1x to 3x without any need to remove or adjust the zeroed portion of your aiming system.







Purpose and Benefits



With iron sights, you have to align your aiming eye perfectly with the sight axis. The eye, the rear iron sight, the front iron sight and the target must all be exactly aligned. Your aiming eye is focused on the front sight, not on the target, and the other eye is typically closed. This technique works very well, but it takes a lot of practice, it tends to fall apart under stress when it's needed most, and it limits your view of the target and the surroundings.



Using a telescopic sight can be a big improvement, but still your eye must be exactly in line with the center of the sight tube, and at the correct distance (eye relief) or you get no sight picture-- an issue that gets more critical with increased magnification. Getting on target can take a significant amount of time. This problem is less severe when using Intermediate Eye Relief (I.E.R.) or Extended Eye Relief (E.E.R.) scopes. Telescopic sights do solve the issue of focus-- the aiming reticle will appear on the same focal plane as the target, so both are in focus at the same time. With magnification however, you're typically aiming with one eye closed, which can reduce your awareness of the surroundings, while the field of view through the scope is limited.



With either a reflex sight or a holosight you do not need to have your eye aligned with the sight tube, or sight axis, and eye relief is no longer an issue. You can be looking through the sight from a position that would be useless for iron sights, or for a telescope, and still you can use the aiming reticle successfully. The shooter no longer needs to focus with one eye on a front sight while the target appears out of focus. As with a telescope, the aiming reticle and the target field will appear on the same focal plane. Unlike a telescope, electronic sights allow the shooter to pay full attention to the target area using both eyes, while the aiming reticle is suspended within the full, natural field of view. For these reasons (reticle in focus with the target, no need for perfect eye-to-weapon alignment, and retention of full field of view) electronic sights are faster on target and are often said to allow for improved "situational awareness".



Additionally, the iron sights, being typically black, can become virtually invisible in low light or when aiming into a dark area or a black target. The aiming reticle in a telescopic sight can suffer the same pitfall. Some telescope manufacturers have addressed this with illuminated reticles. There are iron sights that have tritium powered beta lamp inserts, and others that employ a fiber optic insert in the front sight post. In a reflex sight or holosight, the reticle consists of a bright colored, glowing dot or triangle, etc., so by its nature it is easily seen in a wider range of lighting conditions. If you can see a target, you can use an electronic sight to take aim.







Reflex Sights



Most "red dot" type sights fall into this category. The term "reflex" refers to the fact that the aiming reticle (the dot, triangle, chevron, circle, etc.) is projected forward, from a point behind the objective lens, and is then reflected off the back of the objective lens assembly toward the shooter's eye. The objective lens is therefore a partial mirror, which also means that it will not allow as much light to pass through it as would a regular lens, such as you would find in a regular telescope. In a quality reflex sight this is hardly noticeable, because the reflective lens coating will have been carefully tuned to reflect only the wavelength of light emitted by the reticle illumination system (usually a light emitting diode). LEDs have a very narrow band output, and are ideal for this application. Some reflex sights use ambient light gathered by a fiber-optic system, and others are supplemented by a tritium beta lamp unit for reticle illumination in low light conditions. These latter two rely upon a wider band of light wavelengths and the lens coating will be adjusted to reflect this greater bandwidth, so they will tend to alter the color of the light passing through the sight a little more than the diode type sights. All other visible wavelengths will pass through normally, and since the wavelength (color) that is being reflected is such a narrow slice of the visible spectrum, you scarcely notice it's missing when you look through the sight. Since the lens coating reflects exactly the color of the reticle, the reticle is very efficiently reflected back to your eye and is clearly visible against the target field. A reflex sight contains no laser, and no significant amount of light is emitted forward (toward the target) with this technology.



Reflex sights can be found in two general configurations; the so-called "head-up" type (where else the shooter's head would be is not clear. The name apparently comes from their vague resemblance of a fighter jet's head-up display). These have just one lens assembly, and the reticle source point will be below and behind the lens ("behind" meaning closer to the shooter and farther from the muzzle). They don't look anything like a "scope". These would include the C-more, Trijicon Reflex, etc.. The other configuration looks more like a "scope" in that it has a tubular body with a lens element at each end. Tube reflex sights can be mounted lower on the firearm, since the reticle projection point, and its power source, are typically mounted off to one side rather than below the optical axis of the sight. On a flat-top M-16 type rifle, where you need plenty of sight height anyway, this is no benefit, but on most anything else, the lower mounting option provided by the tube bodied sight can be a real benefit. Tube type reflex sights include Aimpoint, Trijicon Tripower, Leupold, Tasco, Bushnell, and countless others.







Holographic Sights



Whether it's called a "Holographic Weapon Sight" a "Holographic Diffraction Sight" or a "Holosight" it's basically the same technology. A sighting reticle is superimposed on your view of the target field by way of a laser transmission hologram. Without getting too much into the process, it means that a photograph of the reticle is taken using a very careful application of laser light. Google for "holography" and you'll find detailed information on the subject. The hologram, sandwiched in glass, forms a window through which you view your target. Since there is no reflective coating, a holographic sight will not alter the normal light going through it's sighting window any more than a regular piece of glass, or so it seems to my eyes. There is indeed a laser in a holographic sight. The laser beam is spread out by a lens and shone backward, toward the shooter, from a position in front of the hologram window, creating a reticle image that, according to some literature, appears at a virtual 50 yards in front of you. If so, it would mean that a holographic sight would work much like an aperture sight with a sight radius of 50 yards and an aperture of about an inch and a half. The reticles, being holograms, could in theory be any shape or configuration, including three dimensional shapes. All the holographic sights we've seen are of the "head up" type, so they cannot mount as low on the weapon as a tube sight. There may be a good reason why a holosight cannot have its laser module mounted on top or to one side, allowing the sight to mount lower on the weapon, but if so, I have not heard a case for it. Since the hologram window consists of a flat glass panel, the problem of glint being noticeable to one's prey will be less of an issue, compared to a conventional optic having a convex objective lens. This would make the holographic sight slightly more stealthy in that regard. We know of one manufacturer of holographic weapon sights-- Electro-Optic Technologies. The sights are found under the names EOTech and Bushnell. They have (or had) a selection of different reticles, but their standard 1 minute dot with 65 minute circle is excellent, most especially when engaging a moving target.



The laser light coming through the hologram is polarized. While most shooters may never need to know this, it can be an issue when using polarized shooting glasses. I have an old version of the Bushnell Holosight, and the polarity of its hologram is such that it is greatly attenuated when viewed through polarizing glasses. I suspected that all polarizing glasses, intended for cutting glare when worn outside, under the sun, would be built with the same polar orientation. I made some calls to an optometrist, who did some checking for me and was able to confirm this. There is a more or less ideal compromise orientation to the polarizing filters that make up the lenses in your polaroid glasses, so all manufacturers use approximately the same orientation. I called the good folks at EOTech, and they were aware of this. All Holosights and military Holographic Weapon Sights (HWS) made today have the hologram's polarity at an angle that makes for uninhibited viewing of the reticle when wearing polarizing glasses. This is good news. You can now enjoy the benefits of wearing polarizing glasses in the field, and still use your holosight to full effect.



In the field, a reflex sight and a holographic sight are used exactly the same way and for the same reasons. They are completely different technologies used for solving the same problems. Neither one of them is a "laser sight".







Laser Sights



A laser sight is merely a laser pointer designed to tolerate firearm recoil, and having windage and elevation adjustments for zeroing the laser with the firearm. The laser light needs to make the round trip from the firearm, to the target, and back, and still be visible to the shooter. The visibility of the laser dot is therefore affected by distance, tremendously affected by the reflectivity of the target, by the brightness of the daylight, and by atmospheric conditions like fog, rain, snow, dust and smoke. A laser sight therefore needs a lot of power compared to a reflex sight or holosight. Unfortunately, the government has chosen to limit the power of lasers available to us peons, presumably because we are incompetent, and present a danger to ourselves and others. Lasers also cannot be seen at all in clear air unless they are actually falling upon an object (imagine your scope's cross-hairs being invisible until you're right on the target). This is usually not a problem indoors, but outside it can be debilitating (think trap shooting, or think about a target that is against nothing but sky, or against a very distant background). No dot at all can be seen in that case unless the laser is shining directly on the target. You can see the beam in fog, etc., in which case the beam points the way directly to the firearm, like a lighthouse beacon. One benefit to a laser is that it can be used to point out objects to people other than the shooter, since its dot falling on the object can be seen by anyone. The dot, if it's the right wavelength and power, can also be detected by the guidance system on a laser guided missile or bomb. In military applications, these "laser designators" can be weapon mounted, so as to serve the purpose of guiding ordnance into a target, or for pointing out a target to the crew of a gunship, etc., and can also be used to aim the firearm. Infrared lasers make for a stealthy laser sight or designator when used with night vision devices. Lasers do not require the firearm to be shouldered, or brought into the shooter's line of sight, in order to be useful for aiming.



We hear tales from the sand box that visible lasers, whether zeroed to the rifle or not, make for an effective crowd control device. Once a trouble maker notices the bright red dot on his chest, he "gets polite real fast". This is an application I had not considered, and I would say it's a very specialized application. Still, it could be better than having to actually shoot someone just to get their attention.



I can see a use for lasers in casual plinking too, or for Boomershoot, wherein a spotter could use a laser to point out targets to the shooter or vise versa. This could become a real problem though if a lot of people at one event are using this technique-- who's going to know whose laser dot is whose? Same goes for a law enforcement situation where several officers may be painting laser dots at the same time (is that my dot or is it my buddy's dot? What if I pull the trigger and realize later that I was looking at someone else's dot?) The thing to remember is that a laser, unlike all other sighting devices, is an active sensing device. It is not private.



A holographic sight is not a laser sight, in that it does not project a laser beam onto the target, and does not suffer from the above quirks. Rather, it uses a wash of laser light, shone toward the shooter, to display a hologram.



A reflex sight is not a laser sight either. It provides a red aiming dot, similar in appearance to a laser dot, but it has no laser. It puts the dot (or other type of reticle) backward, into your eye.







How Far Does it Go?



When discussing reflex and holographic sights, we are often asked, "How far does it go?" The answer to this question is "Just a few inches". The person asking the question is thinking about a laser sight, when we're having a discussion about a reflex sight. The reflex sight's reticle image travels from the sight body back toward your eye. Unlike a laser, you can point the sight at the open sky or at the moon and see the reticle just as well. You can use reflex sights just as easily at the weapon's maximum range as you can at 5 feet.



A laser sight is limited in its useful range by atmospheric and lighting conditions. In ideal conditions (twilight with a highly reflective target) a laser will be useful at many times the distance you could use it in bright sunlight with a light absorbing target. I've had a very hard time using a laser at 7 yards in direct sunlight, and I once used a laser at about 200 yards with no trouble because the target was in shadow at dusk. Quality reflex sights and holographic sights have no such limitations.







Field of View



Field of view refers to the angle, or the width, or the angular size, of the image viewable through the sight (30 feet at 100 yards, for example, etc.). Field of view is an important issue when using the more familiar telescopic sight-- You want a wide field of view so you can find the target, see what's going on around the target, or in some cases to be able to see the whole target rather than a small portion of it. For this reason, manufacturers have been publishing F.O.V. specifications for their telescopes for years. Field of view specs matter very little if at all when using 1x electronic sights. Certainly, field of view is always important, especially in close quarters battle, in hunting, or in IPSC competition. However, a 1x sight is designed for use with both eyes open. Your field of view is therefore not limited by the sight, but only by the design and condition of your eyeballs. Field of view, per se, through a 1x sight therefore hardly matters.



All the electronic sight is doing is providing a reticle, superimposed on your natural field of view.



What matters to us when using electronic sights is what I will call Maximum Off Axis Displacement (MOAD) defined as the maximum distance from the center axis of the sighting window (right, left, up or down) at which the eye can acquire and use the reticle. It could simply be termed Effective Viewing Area (EVA). The M.O.A.D. may be loosely related to field of view, but when sighting with both eyes open F.O.V. does not correctly identify the issue.



(This is not to be confused with eye relief, which is the required distance between the sight's ocular lens and the eye. 1x electronic sights have unlimited eye relief, so they can be mounted at any point along the weapon.)



If the sight is too close to you, there will be a small blind spot where the body of the optic blocks the view of both eyes at once. The unlimited eye relief of these sights allows mounting the optic forward of the receiver, farther from the eye. At UltiMAK we design our rifle optic mounts to take advantage of this unlimited eye relief, putting the optic forward of the receiver where it eliminates the blind spot, and down low, closer to the iron sight axis where your rifle's comb was designed to place your aiming eye. Achieving these goals requires overcoming more design challenges, better engineering and more sophisticated manufacturing processes, but the payoffs in ergonomics (in a better "fit" to the shooter) are more than worth it.







Occlusion



Often, I hear people talking about a dot, or large triangle reticle "covering" too much of the target. This is a nonsensical issue. First, there is significant occlusion resulting from the front and rear iron sights, and I've never heard a complaint about that. Second, aiming with both eyes open, there is no occlusion of any portion of your naked-eye field of view. Your big triangle reticle may "cover" part of the world for your right eye, but your left eye is free to see it. Whatever may be obscured from one eye will be visible to the other. As long as you have two working eyes there is no such thing as occlusion when using an electronic sight, except when you want it (see below).







Washout



This may be a real issue in some cases, but it needn't. Washout occurs when aiming into a bright area, causing the reticle to become lost in the glare. A very bright reticle setting, as found in a high quality sight, is one solution to this problem. There are at least two others;

1. Close your front lens cover. Now you cannot see through the sight at all-- field of view = 0 Degrees (zero feet at 100 yards). With the front lens cover closed on a reflex sight, your aiming eye sees the glowing reticle against a black background, no matter what. Your other eye sees a largely unobstructed view of the world. Your brain can blend the two images, and assuming you have two useable eyes, you will see your aiming reticle against the target field under any lighting conditions. Enter the Occluded Eye Gunsight (O.E.G.). Close the front cover of your Aimpoint, for instance, and you have, effectively, an O.E.G..

2. Install a polarizing filter on your reflex sight. I'm not sure of their thinking behind them, but several optics manufacturers have come up with dual polarizer attachments that can be (tediously) adjusted so they cross, blocking out most of the incoming light. This is an Attenuated Eye Gunsight (A.E.G.?) or Mostly Occluded Eye Gunsight (M.O.E.G.?) and it will serve the same purpose as the closed lens cover. You can also rotate the two polarizers to where they are aligned, providing a view in polarized light. The latter can be very effective in cutting glare if you align the two filters at the necessary angle (if you're using polarizing glasses, this would already be addressed, and placing a polarizer on your sight will then possibly turn down the light).



In theory, this could be done with a holographic sight by placing a filter or cover forward of the laser window. It would reduce or block light coming from the target area, and allow the laser light to pass through unobstructed, giving you an Occluded Eye Holosight (OEH?). As far as I know, the holo manufacturers have not addressed this. The high intensity reticle settings tend to do the job pretty well though.



Update 2008: GG&G now has a front and rear flip-up hologram cover system for most EOTech sights, available here. (we will refrain from calling it a "lens" cover, since the hologram is not a lens).







Co witnessing



It's often difficult to grasp the true simplicity of a new concept, so we make it complicated as a way of justifying our misunderstanding. So it is sometimes with co witnessing. The term means only one thing-- The ability to use either the optical sight or the iron sights, by changing almost nothing other than your attention. You are able to use the iron sights by looking through the lower portion of the electronic sight's viewing area. It does not mean that the iron sights and electronic reticle are used at the same time. Co witnessing simply gives you a redundant sighting system in case one of them fails, or you forget to switch on the electronic sight.



We occasionally have people tell us things like, "I finally got my dot to co witness about a quarter inch above the iron sights..." Again-- Nonsensical. If your electronic sight is zeroed for the same distance and wind as your iron sights, and you line up your iron sights while your electronic sight is turned on, you will see the electronic reticle aligned with the top of the front iron sight post. When using the electronic sight, you would typically look just over the top of the iron sights, such that the electronic sighting reticle appears to float above the iron sights. Again, the apparent position of the electronic reticle within the sighting window is of no consequence and it depends on the position of your eye. Once zeroed, the reflex dot can be at the very bottom, the extreme left, right, or top of the viewing area and it still represents your proper aiming point.







Zeroing



Electronic sights of all types are zeroed with the same technique used for a regular scope. They have separate windage and elevation adjustments, calibrated in minutes of angle (MOA). One difference is that you usually don't have the typical cross-hairs to use as a visual guide for leveling the sight on the firearm. Leveling of a dot sight is done by eyeballing the exterior of the sight so the windage and elevation caps are square with the firearm (or more importantly, level and square with gravity as you hold the weapon in a shooting position). Unlike a tubular sight, a holosight, or other "head up" type sight has a fixed orientation on the mounting rail. The zeroing process itself is the same as with any scope. One exception is that with co witnessing, assuming the iron sights are zeroed, you can come very close to a "zero-shot zero" simply by sighting down the irons and adjusting the dot to align with them, representing your point of impact. Always confirm zero on paper at the desired distance for your irons and your electronic sight separately before trusting them.



There are some tube reflex sights (Aimpoint for one) that can be mounted with the switch module on either the left or the right side. This has resulted in confusion for some, because one adjustment will be marked "UP-R" and the other is marked "UP-L". If the adjustment happens to be on top, it moves your point of impact "UP" when turned in the direction of the arrow. If it happens to be situated on one side or the other, it moves your bullet impact point either "L" or "R" as marked. Simple enough.



I submit that since most military rifles' iron sights have Bullet Drop Compensated (BDC) settings, some calibrated out to 1,000 meters, it stands to reason that an enterprising optics manufacturer could show strong precedent for a BDC electronic sight. After zeroing at the prescribed distance, you crank the elevation knob to the appropriate range setting and aim dead on, just like you would with iron sights. The adjustments could be mechanical or electronic. A transparent LCD reticle display for instance, could be controlled by a simple computer, programmed for the trajectory of any load. For a 1x or 2x sight, a "screen resolution" of 1 MOA is generally going to suffice. Aimpoint has taken a step in this direction, producing a mechanical, externally adjustable mount with three quick-select range settings, designed for their MPS II reflex sight. BDC presets are practical for the military because they use standardized loads fired from standardized barrels. For us civies, who use a mind boggling variety of loads from an infinite continuum of barrels, an adjustable preset system would be suggested. The concept of an externally adjusted optic is certainly nothing new. Maybe it's time to take a few closer looks at it, but with electronic sights in mind.



Update: We hear from our super-secret inside sources that a prominent optics company is working on a BDC reticle for their current line of military-grade 1x electronic optics. It will have multiple aiming points, each calibrated for a separate distance, based on a common military cartridge/weapon system's trajectory. Hopefully it will have a built-in bubble, because if you're lobbing rounds out to 600 or so, cant will become an issue.



Update #2: EOTech, a division of L3 Communications, is now producing their new BDC holographic rifle sight reticle. It is built in three variations at this time: One for the M4 Carbine (5.56 NATO) one for the M240 and other 7.62 NATO (.308 Win) setups, and another for the M2 machinegun (50 BMG). They also now have a magnifier that can be mounted behind the sights, allowing instant conversion from 1x to either 3x or 4x (depending on model) and back again using QD mounts. Look for these new products soon here at UltiMAK.





