The majority of CCOs (Close Combat Optics) have been in the form of the red dot sight, such as the Aimpoint M2 and Trijicon ACOG Reflex sight. The Eotech series of sights, known as "holosights" are the next generation in CCOs.
I bourght my Eotech 552 HWS (Holographic Weapon Sight) simply because I just didn't like the tubular nature of the aimpoint. The Eotech carries the same holographic three dimensional properties as a modern fighter aircraft HUD (Head's Up Display) and thus does away with the conventional tubular design completely, giving the operator a full periphiral vision which can be extremely vital in a combat situation. Not only this, but the Eotech uses a 65 MOA (Minute of Angle) ring and a 1 MOA dot in the middle. This gives the best comprimise between speed and accuracy.
The durability of the sight is another reason why I purchased it. It is a very, very tough little piece of equipment. The sight itself is made of a hard plastic material that has been drop tested to military specifications. The internals are also encased in a resin to absorb the shock of impact. In addition to this, a heavy metal (and replacable!) "roll bar" hood is placed over the outside of the sight window. I myself have accidently drop tested this, by removing the sight from the rail, and having it slip from my hands, and land on concrete. The only damage it sustained was a minor scratch.
The window itself is designed to be as versatile as possible. As the reticle is recorded and viewable everywhere on the window, the sight will still function properly and maintain it's point of aim/impact. If the screen is obstructed with mud, snow or even in an extreme case, the window itself is shattered at one point, but other areas of the HUD are still alright, then the user can view the reticle and continue to use the sight effectively. Whilst a BB hit is unlikely to shatter the window, you at least have that peace of mind knowing that the sight will still function.
Unlike red dot sights, there is no muzzle side reflections in any way, and the reticle is only viewable by the operator. Even GEN III nightvision equipment cannot pick up glare from the HWS. The surface for the HUD is flat and treated with an antireflective coating which eliminates glare and reflections. There is simply no need for costly filters such as Killflashes which also dim the light that travels through the sight, thus rendering it less effective.
Unlike other sights, it uses more conventional and easier to source batteries, which are N cell and AA. Due to the massive size difference in these two battery types, there is two different sizes of Eotechs on the market. The shorter, stubby nosed one accomodates the N Cell batteries whilst the considerably longer version takes the AA which can be found in just about any store you come across. I went for the 552, which uses the AA batteries. This version costs more but is worth it in the long run.
The Eotech HWS also comes with a built in picatinny railgrabber, so you can put it straight onto the rifle (if the rifle has a rail mounted to it, of course). With the Aimpoint M2 you have to buy a 30mm mount for it, which just adds to the cost. There is a throw lever ACCUCAM mount by GG&G, which takes the place of the standard one, but this is only needed if you think you're going to be taking it off in a hurry, or just paranoid that the screw will come loose and the sight falls off the rifle! However, this is extremely unlikely.
It really is hard to compare the Eotech with a sight like the Aimpoint M2. It's not so much like comparing apples and pears, but apples and very large grapefruits. The age of the red dot is dying out, and the HWS is taking it's place. I can only say good things about the Eotech.
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