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Electronic Sights; A look at why they exist, how they work, and how you use them. Photos with model: Oleg Volk For this article, we define electronic sights as anything within the three general categories; reflex sights, holographic sights, and laser sights. Some refer to them as "tactical sights" but a high power, mil dot telescope could be "tactical" just as well. One UltiMAK user from down south refers to them as "high speed, low drag gringo s#%t". I suppose that works, but it's non specific. Other types of targeting devices are certainly "electronic" but they are not discussed here. There are reflex sights that do not use electricity, and so are not strictly "electronic" but they are included here. For convenience, the different sections are accessible directly; Application Purpose and Benefits Reflex Sights Holographic Sights Laser Sights "How Far Does it Go?" Field of View Occlusion Washout Co Witnessing Zeroing Anecdotes on Reliability |
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. |
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. |
Anecdotes on the subject of reliability
We at UltiMAK bought our first Aimpoint, the old model CompML, about four years ago as of this writing. It has been used in practically every test firing/product torture session since, and has logged well over 7,000 rounds in all weather, from boiling hot on a smoking AK barrel to sub zero. More than once it has been taken to a trade show and left on all day. It still has the original battery and is going strong. The more recent Aimpoint models have a new diode that uses a fraction of the current our old sight uses, so the battery in the new models lasts approximately 30 times longer. If the battery is replaced, as a precaution, every two or three years, the average recreational shooter will never experience a battery failure unless the sight is left on for weeks, months, or in the case of the new Aimpoints, years at a time while it's in storage. The Trijicon Reflex, Reflex II, and the new Tripower can be used for a lifetime without batteries. They have a 12-year tritium beta energy source, providing constant-on reticle illumination for low light conditions. After 12 years, the tritium illumination unit, or beta lamp, can be replenished at the factory. For daylight, they have a fiber-optic system that gathers ambient light and pipes it in to light the reticle. The Tripower has a diode that can be powered with a battery, but its battery supply is only there as a supplement to the fiber-optic illumination system for situations in which a super bright reticle is required (see above under "washout"). We have a military pattern M1 .30 Carbine with UltiMAK mount and an old Bushnell Holosight. Within the first few days of shooting the brand new carbine, the rear iron sight body came loose in its dovetail slot and fell off. The front sight has since shot loose. It may be that iron sights are an "old standby" upon which one can rely when the new, high-tech gizmos fail, but in this case it was the other way around. The Holosight has been transferred from one firearm to another, used in all weather conditions, subject to .308 rifle recoil, and it still works like new. I own a new Winchester 1894 "Wrangler" .30-30. I had my kids out for a drive in the mountains, when we decided to take out the Winchester and do some plinking. We were missing terribly, only to discover that the rear sight elevation wedge had fallen out inside the case. It's a perfectly good rear sight design, but it got bumped in just the wrong way as it was being put in the case, and the wedge popped out, throwing the elevation off by a mile. Update; The Winchester's front sight has now come loose, and caused us to waste more ammo chasing a wandering zero. The rifle has fired a total of no more than about 200 rounds since it was made - not enough to equal one typical day of test shooting at UltiMAK. Then there is the Mini-14 Ranch model we bought new for testing our M4-B prototype. The Ruger is a truly great work of engineering. The first day at the range left us crawling on the ground, looking for the rear sight after it had shot loose and fallen off. We had the same experience with a Mini-30. Ruger, to their credit, has since redesigned the rear irons. I once had a brand new Beretta Tomcat pistol. It was a flawless performer, but it came from the factory with a drift adjustable rear iron sight that was so far to one side the bullets were hitting two feet from point of aim at 20 feet. I was able to use a brass punch to drift it into a reasonable position, but it was not something I could have done at the range. A new SKS of mine needed a small correction in front sight elevation so the calibration marks on the rear sight would be meaningful. The split screw front sight post, which is a fine design, broke in half due to shock and recoil before I got the chance to move it. Bad heat treat apparently. Of all the optic sights I've used, I disliked the cheap ones due to poor optical quality and quit using them, so none of them ever got around to failing. Left with the better ones, I've used them for thousands of rounds of testing, target shooting, plinking and hunting, and they have never failed, except one-- a relatively inexpensive telescope mounted on a 10/.22 sitting in the back of my pickup in a soft bag for a year. My kids had stepped on it and the cheap mounting rings were bent. While optic sights can and do fail, it just happens that my personal experience with the reliability of optics has been far better than with iron sights. Please don't accuse me of claiming that optics are tougher than iron sights. I'm not. I have merely related my personal experiences. Others will not doubt have had different experiences. One thing is certain; Iron sights are not the end-all, fool proof, always-there-as-a-last-resort-no-matter-what aiming system that some might think. Understanding, caring for, and regularly practicing with your gear is the key. |
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