Tactical rifles, especially when equipped with a Picatinny or Weaver rail on the top of the upper receiver, are capable of accepting a wide variety of tactical scopes and sights. The type of scope or sight put into service should reflect the needs of whatever tasks the rifle is needed to perform.
A tactical scope for an AR-15 used at short range will have different requirements than a tactical scope meant for use on a rifle chambered in 308 Winchester and used at long range. Likewise, tactical scopes mounted on rifles intended for extreme ranges such a 338 Lapua Magnum or 50 BMG.
The red dot sight
In its role as a combat rifle, red dot sights are the most popular as they allow for rapid target acquisition. Red dot sights are made by a multitude of companies ranging from low quality imports for under $100 to models costing close to $1000. The most popular brands in this category include the Vortex Strike Fire, Burris fast Fire and the various Aimpoint models.
The term “red dot sight” is a bit of a misnomer as the reticle can be represented by a standard crosshair and the color green is being used with more frequency. Red dot sights project a visible red dot into the focal plane of the scope. This is usually powered by an LED (Light Emitting Diode) and battery life is measured in years as opposed to hours. The shooter superimposes the dot on the target and it acts as the point of aim.
Another one of the benefits of the red dot sight is the ability to keep both eyes open to allow the shooter to scan for additional targets or threats. This is desirable in self-defense, military, police and competitive three-gun shooting scenarios. It has also become popular among hunters.
The primary drawback to the red dot sight is the lack of range. Based on the ability of the shooter, these sights are not generally usable beyond 200 or 300 yards. There are, however, companies offering magnifiers that can be mounted behind the sight to extend the range of the shooter when necessary.
The holographic sight
Similar to the red dot sight in principle is the holographic weapon sight. The concept of the holographic sight was based on Synthetic Aptitude Radar (SAR) and the system was originally used on US fighter planes. As the laser sights used in SAR became smaller and able to be made more cheaply, the US military asked that they be developed for use on small arms.
A holographic sight uses a laser to generate and project a reticle into the user’s line of sight. The reticle is projected by means of a hologram onto the glass in the sight’s prism. The EO Tech sight is said to be completely free of parallax regardless of distance or viewing angle. Parallax refers to an error by which the scope’s reticle appears to move in comparison to the target when the user moves his head behind the sight in a lateral direction: either up and down or left to right
The first of these designs was first developed by EO Tech, a company based in Ann Arbor, Michigan, in the early 1990s. EO Tech partnered with Bushnell in the late 1990s to produce a commercial variant to test it among hunters and competitive shooters. EO Tech went into full production of a MILSPEC version and made some improvements for durability incorporating what it refers to as a “roll bar” surrounding the unit to protect the sight from damage.
The most popular model is the original EO Tech 553. EO Tech sights which have had their glass damaged by gunfire were found to still work apart from the shattered view.
This sight runs on either one or two batteries depending upon the model. Single battery sights have a battery life of close to 600 hours, whereas the two-battery version can run for 1000 hours. EO Tech sights have an integral mount that can attach to a Picatinny or Weaver rail.
The reticle display of the EO Tech allows the shooter to maintain his peripheral vision and keep both eyes open while shooting as opposed to using a scope with a tube. The company maintains that the sight is visible to 300 yards on target and a magnifier with a “flip to the side” mount is available to engage targets at longer distances. The EO Tech sight is fully compatible with night vision devices as well.
A number of other companies manufacture similar sights for the shooter who may not need a robust version or one that is not night vision compatible.
The fixed power scope
Probably the oldest of the tactical scopes is the fixed power scope. These are conventional tube styled telescopic sights that are set to a fixed power of magnification. Although the scopes, themselves, are simple in nature and appear very limited, they are among the most diverse as a family ranging from 1X or no magnification up to 24X for long distance shooting.
They are prized as a tactical scope for their simplicity, the lack of the ability to zoom means there are less moving parts and therefore fewer chances for the scope to fail.
Low powered scopes in the 1X to 4X ranges are used for close range work in self-defense, military, police, dangerous game hunting, and competitive three-gun shooting scenarios. A sub-variant of this group is known as the “Scout Scope” and these types of scopes are mounted on the barrel or forward part of the rifle or shotgun’s receiver to allow for rapid target acquisition.
Fixed power scopes in higher magnification ranges are often used on sniper rifles, such as the fabled USMC Unertl 10X scope that was used on the M40 Sniper Rifle for over 3 decades.
The Collimator sight
Collimating sights have been in use since the 1940s. The earliest of these sights had no optical window and were used on mortars and artillery pieces. In the 1970s they were redesigned with the use of fiber optics and tritium as the “occluded eye gun sight” (OEG). The shooter did not look through the sight but rather an optical illusion was created while looking at the sight with both eyes opened causing the reticle to be superimposed over the target. These sights require less illumination for the reticle for the same level of usability, due to the high contrast black background behind the reticle. For this reason occluded eye gun sights were more practical for use on small arms before low power consumption illumination sources such as LEDs became commonplace.
A company known as Trijicon was the original importer of the Armson OEG and over the years made improvements to the concept in what became known as the ACOG (Advanced Combat Optical Gun sight). These sights work in principle as a combination of the fixed power scope with the collimating reticle. In the case of the ACOG, the reticle is etched into the glass and filled with radioactive tritium, allowing the scope to be used at night time or in low-light conditions. Most versions incorporate fiber optics to produce the same effect of the colored reticle for use during the day time.
The Variable Powered Scope
In some ways the variable powered scope can be the most diverse scope for use on a tactical rifle. These scopes allow the user to change magnification from as low as 1X (or no magnification) to as high as 50X. Typical ranges for a tactical variable powered scope are 4-16X and 6-20X.
Tactical variable powered scopes are typically built stronger than their hunting counterparts to resist damage to the optic. Many of these scopes rely on specially designed reticles used to engage moving targets, estimate ranges or may incorporate additional illumination for lowlight scenarios.
If the shooter sets the magnification on a lower powered setting it will aid in target acquisition because the field of view is greater than on the higher settings. Once the target is acquired, the shooter can then choose to zoom in on the target for a more precise shot.
Some of the variable powered scopes that begin at a 1X setting are as fast for the shooter to get on target as a red dot or holographic sight, but provide enough zoom to go out to 6X magnification. Unless you are looking for a dedicated long range tactical optic, these may be your best choice.
The Mil Dot reticle
One of the most popular reticles to be found on a tactical scope is known as the Mil Dot reticle. The Mil Dot reticle was developed for use by the USMC on the Unertl 10X scope. Basically it is a traditional crosshair with thick posts with a series of 10 milliradians (also known as mils) between the posts with each one represented by a dot spaced 1 mil apart. There is no central dot on a true Mil Dot reticle. A milliradian equals 1 yard at 1000 yards or 1 meter at 1000 meters. This allows a shooter to determine the range to a target if he knows the size of his target and has a Mil Dot calculator or slide rule to help with the calculations.
On a true Mil Dot scope the milliradians are slightly shaped like footballs as opposed to true circles.