M16, M4 and AR-15 Aiming Devices

Every weapon has a method of aiming, that is either fixed or attached to operate the weapon effectively. Soldiers must be familiar with the various aiming devices, how they operate, and how to employ them correctly to maximize their effectiveness. This chapter provides the principles of operation of the most widely available aiming devices, and provides general information concerning their capabilities, function and use.

An aiming device is used to align the Soldier, the weapon, and the target to make an accurate and precise shot. Each aiming device functions in a different manner. To employ the weapon system to its fullest capability, the Soldier must understand how their aiming devices function.

The following aiming devices are described within this chapter:

  • Iron. Iron represent the various types of mechanical sighting systems available on the weapon. They are available in two distinct types:
    • Iron sights (rear aperture and front sight post).
    • Back up iron sights (BUIS).
  • Optics. These are optics predominantly for day firing, with limited night capability. The optics found within this manual come in two types:
    • Close Combat Optic (CCO).
    • Rifle Combat Optic (RCO, previously referred to as the Advanced Combat Optic Gunsight or ACOG).
  • Thermal. These are electronic sighting systems that provide a view of the field of view (FOV) based on temperature variations. There are numerous variants of thermal optics, but are grouped into one type:

Thermal Weapon Sight (TWS).

  • Pointer/Illuminator/Laser. These aiming devices use either a laser beam, flood light, or other light to aim the weapon at the target. There are three types of pointers, illuminators, and lasers used by the service rifle:
    • Advanced Target Pointer Illuminator Aiming Light (ATPIAL).
    • Dual Beam Aiming Laser–Advanced (DBAL-A2).
    • Illuminator, Integrated, Small Arms (STORM).

 

UNITS OF ANGULAR MEASUREMENT

There are two major units of angular measurement the Army uses: mils and minutes of angle (MOA). These two different units are commonly used terms to describe a measurement of accuracy when firing a weapon, system, or munition. They typically include the accuracy of a specific weapon, the performance of ammunition, and the ability of a shooter as it relates to firing the weapon.

 

MINUTE OF ANGLE

A minute of angle (MOA) is an angular unit of measurement equal to 1/60th of a degree (see figure 3-1). The most common use of MOA is when describing the distance of change required when zeroing a weapon.

One MOA equals 1.047 inches per 100 yards. For most applications, a Soldier can round this to 1 inch at 100 yards or inches at 100 meters to simplify their arithmetic.

 

 

Minute of angle example
Minute of angle example

MILS
The mil is a common unit of angular measurement that is used in direct fire and indirect fire applications. (see figure 3-2)

Mil example
Mil example

This mil to degree relationship is used when describing military reticles, ballistic relationships, aiming devices, and on a larger scale, map reading and for indirect fire.

 

RETICLE
A reticle is a series of fine lines in the eyepiece of an optic, such as a CCO, TWS, or RCO (see figure 3-3) used as a measuring scale with included aiming or alignment points. Reticles use either mils or minute of angle for their unit of measurement.

Close combat optic / Rifle combat optic reticle / Thermal reticle examples
Close combat optic / Rifle combat optic reticle / Thermal reticle examples

 

STADIA RETICLE (STADIAMETRIC RETICLE)
Commonly used in the thermal weapon sight, a stadia reticle provides a means of rapidly determining the approximate range to target of a viewed threat, based on its standard dimensions. The stadia reticle (sometimes referred to as “stadiametric” or “choke sight”) can provide approximate range to target information using width or height of a viewed dismounted target using standard threat dimensions (see figure 3-4).

Stadia reticle example
Stadia reticle example

 

There are two stadia reticles found on the rifle/carbine reticle within the sight of the thermal weapon; vertical and horizontal.

  • Vertical stadia. At the lower left of the sight picture, Soldiers can evaluate the range to the target of a standing dismounted threat.
  • Horizontal stadia. In the upper right portion of the sight picture, Soldiers can evaluate the range to a target of an exposed dismounted threat based on the width of the target.

 

ELECTROMAGNETIC SPECTRUM

A major concern for the planning and use of thermal and other optics to aid in the detection process is understanding how they function, but more appropriately, what they can “see”. Each device develops a digital representation of the scene or views it is observing based on what frequencies or wavelengths it can detect within the electromagnetic spectrum. (Note: Thermal devices see differences in heat.)

  • Thermal optics. This equipment operates in the mid-and far-wavelength of the infrared band, which is the farthest of the infrared wavelengths from visible light. Thermal optics cannot translate (“see”) visible light. Thermal optics cannot “see” infrared equipment such as infrared (IR) strobe lights, IR chemical lights, illuminators, or laser pointers. They can only identify emitted radiation in the form of heat.
  • Image intensifiers (I2). This equipment, such as night vision devices, use the near area of the infrared spectrum closest to the frequencies of visible light, as well as visible light to create a digital picture of the scene. These systems cannot “see” or detect heat or heat sources.

These sights generally operate on the principles of convection, conduction, and radiation (mentioned in chapter 2 of this publication). The sight “picks up” or translates the IR wavelength (or light) that is emitted from a target scene through one of those three methods.

Things to be aware of (planning considerations) with these optics are that they have difficulty imaging through the following:

  • Rain – absorbs the IR emitted by the target, makes it difficult to see.
  • Water – acts as a mirror and generally reflects IR, providing a false thermal scene.
  • Glass – acts similar to water, interfering with the sensor’s ability to accurately detect emitted radiation behind the glass.

Situations, where IR can see better, are the following:

  • Smoke – will not obscure a target unless the chemical obscurant is extremely hot and dense, or if the target is sitting on top of the smoke source.
  • Dust – may interfere with the accurate detection of the emitted thermal signature due to dust and debris density between the sensor and the target scene. Dust typically does not obscure the IR signature unless its temperature is similar to the targets.

Figure 3-5 depicts the areas of the electromagnetic spectrum. It details the various wavelengths within the spectrum where the aiming devices, night vision devices, and equipment operation. It illustrates where these items can and cannot “see” the others, respectively, within their operating range.

 

Electromagnetic spectrum
Electromagnetic spectrum

OPTICS

Optics are sighting aids for rifles and carbines that provide enhanced aim point reticles, and may include magnified fields of view. Optics are specific to day operations, although may be used during limited visibility or night operations. They do not have any method of enhancing low light conditions.

Optics enhance the Soldier’s ability to engage targets accurately and at extended ranges. The available optics for mounting on the M4- and M16-series modular weapon system are:

  • Iron Sight.
  • Back Up Iron Sight (BUIS).
  • CCO, M68.
  • RCO, M150.

 

IRON SIGHT

Some versions of the M4 and M16 come with a carrying handle with an integrated rear aperture. The carrying handle may or may not be removable, depending on the version of the service rifle.

The integrated rear aperture includes adjustments for both azimuth (wind) and elevation. Specific instructions for zeroing these aiming devices are found in the respective weapon’s technical manual.

The carrying handle has two selectable apertures for the engagement situation:

  • Small aperture. Used for zeroing procedures and for mid- and extended-range engagements.
  • Large aperture. Used during limited visibility, close quarters, and for moving targets at close or mid-range.

The iron sight uses the fixed front sight post to create the proper aim. Soldiers use the front sight post centered in the rear aperture. The following information is extracted from the weapon’s technical manual.

 

Carrying handle with iron sight example
Carrying handle with iron sight example

BACK UP IRON SIGHT
The BUIS is a semi-permanent flip-up sight equipped with a rail-grabbing base. The BUIS provides a backup capability effective out to 600 meters and can be installed on M16A4 rifles and M4-series carbines. (See figure 3-7.)

The BUIS on the first notch of the integrated rail, nearest to the charging handle. The BUIS remains on the modular weapon system (MWS) unless the carrying handle/sight is installed. The following information is extracted from the weapon’s technical manual.

 

Back up iron sight
Back up iron sight

 

CLOSE COMBAT OPTIC, M68

The close combat optic (CCO), M68 is a non-telescopic (unmagnified) reflex sight that is designed for the “eyes-open” method of sighting. It provides Soldiers the ability to fire with one or two eyes open, as needed for the engagement sequence in the shot process.

The CCO provides a red-dot aiming point using a 2 or 4 MOA diameter reticle, depending on the variant. The red dot aiming point follows the horizontal and vertical movement of the firer’s eye, allowing the firer to remain fixed on the target. No centering or focusing on the front sight post is required. There are three versions of the CCO available in the force.

 

Note. Re-tighten the torque-limiting knob after firing the first three to five rounds to fully seat the M68.

The CCO is zeroed to the weapon. It must remain matched with the same weapon, attached at the same slot in the attached rail system or be re-zeroed. If the CCO must be removed for storage, Soldiers must record the serial number and the rail slot to retain zero.

 

Note. The weapon must be re-zeroed if the CCO is not returned to the same rail slot on the adaptive rail system.

 

Advantages

The CCO offers a distinct speed advantage over iron sights in most if not all engagements. The adjustments on brightness allow the Soldier to have the desired brightness from full daylight to blackout conditions.

The CCO is the preferred optic for close quarter’s engagements.

 

Disadvantages

The CCO lacks a bullet drop compensator or other means to determine accurate range to target beyond 200m.

The following information is an extract from the equipment’s technical manual for Soldier reference.

 

blank
CCO Reticle, Comp M2 examples

 

 

RIFLE COMBAT OPTIC

The RCO (see figure 3-9) is designed to provide enhanced target identification and hit probability for the M4-/M4A1- or M16-series weapon.

There are several versions of the RCO available for use across the force. Soldiers must be familiar with their specific version of their assigned RCO, and be knowledgeable on the specific procedures for alignment and operation (see figure 3-9 for RCO azimuth and elevation adjustments).

The reticle pattern provides quick target acquisition at close combat ranges to 800 meters using the bullet drop compensator (BDC) (see figure 3-10 on page 3-15). It is designed with dual illuminated technology, using fiber optics for daytime employment and tritium for nighttime and low-light use.

The RCO is a lightweight, rugged, fast, and accurate 4x power optic scope specifically designed to allow the Soldier to keep both eyes open while engaging targets and maintain maximum situational awareness.

 

Advantages

The bullet drop compensator (BDC) is accurate for extended range engagements using either M855 or M855A1 ball ammunition. The ballistic difference between the two rounds is negligible under 400 meters and requires no hold determinations.

This is a widely fielded optic that is rugged, durable, and operates in limited light conditions. The self-illuminating reticle allows for continuous operations through end evening nautical twilight (EENT).

 

Disadvantages

This optic’s ocular view is limited when engaging targets in close quarters engagements. This requires additional training to master the close quarter’s skills while employing the RCO to achieve overmatch against the threat.

The RCO reticle does not include stadia lines. Windage must be applied by the shooter from a determined estimate. The RCO has a specific eye relief of 70-mm (millimeter) or 1.5 inches. If the eye relief is not correct, the image size will be reduced.

The fiber optic illuminator element can provide excessive light to the reticle during certain conditions that produce a glare. The RCO does not have a mechanical or built in method to reduce the effects of the glare created. The increased lighting may interfere with the shooter’s point of aim and hold determinations. Soldiers may use alternate methods to reduce the glare by reducing the amount of fiber optic exposed to direct sunlight during operating conditions.

The following information is an extract from the equipment’s technical manual for Soldier reference.

blank
RCO reticle example

 

 

THERMAL SIGHTS

Thermal sights are target acquisition and aiming sensors that digitally replicate the field of view based on an estimation of the temperature. They use advanced forward- looking infrared technology that identify the infrared emitted radiation (heat) of a field of view, and translate those temperatures into a gray- or color-scaled image. The TWS is capable of target acquisition under conditions of limited visibility, such as darkness, smoke, fog, dust, and haze, and operates effectively during the day and night.

The TWS is composed of five functional groups: (See figure 3-10.)

  • Objective lens – receives IR light emitting from an object and its surroundings. The objective lens magnifies and projects the IR light.
  • Detector assembly – senses the IR light and coverts it to a video signal.
  • Sensor assembly – the sensor electronics processes the video for display on the liquid crystal display (LCD) array in the field of view.
  • LCD array/eyepiece – the LCD array provides the IR image along with the reticle selected. The light from the LCD array is at the eyepiece.
  • User controls – the control electronics allows the user to interface with the device to adjust contrast, thermal gain, sensitivity, reticle display, and magnification.

 

Thermal weapon sight example
Thermal weapon sight example

 

A small detector used in thermal sensors or optics to identify IR radiation with wavelengths between 3 and 30 μm (micrometer). The thermal optic calculates and processes the thermal scene into a correlating video image signal based on the temperature identified. These optics can differentiate thermal variations of 1 degree Celsius of the viewable scene. These variations generate a corresponding contrasting gradient that develops a thermal representation on the LCD screen in the eyepiece.

 

AN/PAS-13 SERIES OF WEAPON THERMAL SIGHTS

 There are several versions of weapons thermal sights (WTS) available for use across the force. Soldiers must be familiar with their specific model and version of their assigned weapon thermal sight, and be knowledgeable on the specific procedures for alignment and operation. The various models and versions are identified in their official model nomenclature:

  • Version 1 (v1) – Light Weapons Thermal Sight (LWTS).
  • Version 2 (v2) – Medium Weapons Thermal Sight (MWTS).
  • Version 3 (v3) – Heavy Weapons Thermal Sight (HWTS).

Weapons thermal sights are silent, lightweight, and compact, and have durable battery-powered IR imaging sensors that operate with low battery consumption. 

 

Advantages

Military grade weapon thermal weapon sights are designed with the following advantages:

  • Small and lightweight.
  • Real-time imagery. Devices provide real-time video of the thermal scene immediately after power on.
  • Long-lasting battery life. Low power consumption over time.
  • Reliable. Long mean time between failures (MTBF).
  • Quiet. The lack of a cooling element allows for a very low operating noise level.
  • One optic fits on multiple weapons. The use of the ARS rail mounting bracket allows for the same optic to be used on other weapons.
  • The F- and G-models attach in front of other aiming devices to improve their capabilities and eliminate the zeroing procedures for the device.

 

Disadvantages

These devices have limitations that Soldiers should take into consideration, particularly during combat operations. The primary disadvantages are:

  • Cannot interpret (“see”) multispectral infrared. These systems view a specific wavelength for emitted radiation (heat variations), and do not allow viewing of all aiming and marking devices at night.
  • Reliance on rechargeable batteries and charging stations. Although the batteries are common and have a relatively long battery life, additional equipment is required to charge them. If common nonrechargeable (alkaline) batteries are used, a separate battery adapter is typically required.
  • Cannot interpret thermal signatures behind glass or water effectively.
  • Thermal systems cannot always detect friendly marking systems worn by dismounts.

 

Weapon thermal sights by version
Weapon thermal sights by version

 

Thermal sight has a wide field of view and a narrow field of view.

Thermal weapons sight, narrow field of view reticle example
Thermal weapons sight, narrow field of view reticle example

 

Thermal weapons sight, wide field of view reticle example
Thermal weapons sight, wide field of view reticle example

 

 

POINTERS / ILLUMINATORS / LASERS

Pointers, illuminators, and laser devices for small arms weapons emit a collimated beam of IR light for precise aiming and a separate IR beam for illumination. These devices operate in one single mode at a time, as selected by the user. The laser is activated by a selector switch on the device or by a remote mechanism installed on the weapon. The basic two modes or functions are:

  • Pointer. When used as a pointer or aiming device, a small, pin-point beam is emitted from the device. The IR beam provides an infrared visible point when it strikes an object or target. The IR beam operates in the 400 to 800 nanometer wavelength and can only be seen by I2 optics, such as the AN-PVS-7 or -14 night vision devices.
  • Illuminator. Typically used to illuminate a close quarters area as an infrared flood light. The illuminator provides a flood-light effect for the Soldier when used in conjunction with I2 night vision devices.

Note. Laser is an acronym for light amplified stimulated emitted radiation, but is predominantly used as a proper noun.

 

The following devices are the most common laser pointing devices available for use on the M4- and M16-weapons.

 

Laser Aiming Devices for the M4 and M16
Laser Aiming Devices for the M4 and M16

Note. The ATPIAL, DBAL-A2, and STORM have collocated IR and visible aiming lasers. A single set of adjusters move both aiming beams. Although the aiming lasers are collocated, Soldiers should zero the laser they intend to use as their primary pointer to ensure accuracy and consistency during operation.


 

AN/PEQ-2 TARGET POINTER/ILLUMINATOR AIMING LIGHT (TPIAL)

AN/PEQ-2 aiming devices are Class IIIb laser devices that emit a collimated beam of IR light for precise aiming and a separate IR beam for illumination of the target or target area (see figure 3-14 on page 3-21). Both beams can be independently zeroed to the weapon and to each other. The beams can be operated individually or in combination in both high and low power settings.

Note. The IR illuminator is equipped with an adjustable bezel to vary the size of the illumination beam based on the size and distance of the target.

The aiming devices are used with night observation devices (NODs) and can be used as handheld illuminators/pointers or mounted on the weapon with the included brackets and accessory mounts. In the weapon-mounted mode, the aiming devices can be used to direct fire and to illuminate and designate targets.

The aiming light is activated by pressing on either the ON/OFF switch lever, or the button on the optional cable switch. Either switch connects power from two AA batteries to an internal electronic circuit which produces the infrared laser. Internal lenses focus the infrared light into a narrow beam. The direction of the beam is controlled by rotating the mechanical Adjusters with click detents. These adjusters are used to zero the aiming light to the weapon.

Once zeroed to the weapon, the aiming light projects the beam along the line of fire of the weapon. The optical baffle prevents off-axis viewing of the aiming light beam by the enemy.

 

caution

The following information is an extract from the equipment’s technical manual for Soldier reference.

 

The AN/PEQ-15, ATPIAL’s (see figure 3-15 on page 3-23) visible aiming laser provides for active target acquisition in low light conditions and close-quarters combat situations, and allows users to zero using the borelight without using NOD. When used in conjunction with NODs, its IR aiming and illumination lasers provide for active, covert target acquisition in low light or complete darkness.

The ATPIAL visible and IR aiming lasers are co-aligned. A single set of adjusters moves both aiming beams, and the user can boresight/zero using either aiming laser. The following information is an extract from the equipment’s technical manual for Soldier reference.

 

AN/PEQ-15, ATPIAL
AN/PEQ-15, ATPIAL

 

 

AN/PEQ-15A, DUAL BEAM AIMING LASER – ADVANCED2

The AN/PEQ-15A DBAL-A2 is a multifunctional laser device that emits IR pointing and illumination light, as well as a visible laser for precise weapon aiming and target/area illumination. The visible and IR aiming lasers are co-aligned enabling the visible laser to be used to boresight both aiming lasers to a weapon without the need for night vision devices. This ruggedized system can be used as a handheld illuminator/pointer or can be mounted to weapons equipped with an M4 or M5 adapter rail system (MIL-STD-1913).

  • Visible light – can be used to boresight the device to a weapon without the need of night vision goggles. A visible red-dot aiming laser can also be selected to provide precise aiming of a weapon during daylight or night operations.
  • Infrared laser – emits a tightly focused beam of IR light for precise aiming of the weapon. A separate IR illumination provides supplemental IR illumination of the target or target area. The IR illuminator is equipped with an adjustable bezel to vary the size of the illumination beam on the size and distance to the target (flood to point divergence).

The lasers can be used as hand-held illuminator pointers, or can be weapon- mounted with included hardware. These highly capable aiming lasers allow for accurate nighttime aiming and system boresighting.

The AN/PEQ-15A, DBAL-A2 (see figure 3-16 on page 3-25) visible aiming laser provides for active target acquisition in low light conditions and close quarters combat situations, and allows users to zero using the borelight without using NODs. When used in conjunction with NODs, its IR aiming and illumination lasers provide for active, covert target acquisition in low light or complete darkness.

The DBAL-A2 visible and IR aiming lasers are co-aligned. A single set of adjusters moves both aiming beams, and the user can boresight/zero using either aiming laser. The following information is an extract from the equipment’s technical manual for Soldier reference.

AN/PEQ-15A, DBAL-A2
AN/PEQ-15A, DBAL-A2

 

AN/PSQ-23, ILLUMINATOR, INTEGRATED, SMALL ARMS

3-65. The AN/PSQ-23 is a battery operated laser range finder (LRF) and digital magnetic compass (DMC) with integrated multifunctional lasers. The illuminator, integrated, small arms device is commonly referred to as the STORM laser. The visible and IR aiming lasers are co-aligned enabling the visible laser to be used to boresight both aiming lasers to a weapon without the need for night vision devices. This ruggedized system can be used as a handheld illuminator/pointer or can be mounted to weapons equipped with an M4 or M5 adapter rail system (MIL-STD-1913).

  • Laser range finder – provides range to target information from 20 meters to 10,000 meters with an accuracy of +/- 1.5 meters.
  • Digital magnetic compass – provides azimuth information and limited elevation information to the operator. The azimuth accuracy is +/- 0.5 degrees to +/- 1.5 degrees. The elevation accuracy is +/- 0.2 degrees. The DMC can identify bank or slopes up to 45 degrees with an accuracy of +/-

0.2 degrees.

  • Visible light – provides for active target acquisition in low light and close quarters combat situations without the need for night vision devices. It can be used to boresight the device to a weapon without the need of night vision devices. A visible red-dot aiming laser can also be selected to provide precise aiming of a weapon during daylight or night operations.
  • Infrared laser – emits a tightly focused beam of IR light for precise aiming of the weapon. A separate IR illumination provides supplemental IR illumination of the target or target area. The IR illuminator is equipped with an adjustable bezel to vary the size of the illumination beam on the size and distance to the target (flood to point divergence).
  • Infrared illuminator – the STORM features a separately adjustable IR illuminator with adjustable divergence. It is fixed in the device housing and is set parallel to the rail mount.

Note. The STORM’s LRF and DMC may be used in combination to obtain accurate positioning information for targeting purposes and other tactical applications.

 

The integrated visible aim laser (VAL) and illumination lasers provide for active, covert target acquisition in low light or complete darkness when used in conjunction with night vision devices. The STORM is also equipped with a tactical engagement simulation (TES) laser allowing it to be used in a laser-based training environment.

The AN/PEQ-15A, DBAL-A2 visible aiming laser provides for active target acquisition in low light conditions and close-quarters combat situations, and allows users to zero using the borelight without using NODs. When used in conjunction with NODs, its IR aiming and illumination lasers provide for active, covert target acquisition in low light or complete darkness. The following information is an extract from the equipment’s technical manual for Soldier reference.

AN/PSQ-23, STORM
AN/PSQ-23, STORM

 

 


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