Guilding the rifle?
The downturn of installing add-ons to a rifle is that obviously the centre of gravity will be affected and the weight will increase, and saying weight means inertia when traversing the rifle, especially if the add-on weight is far from CG, which means that compared to the naked rifle it will take a few milliseconds more to trail the muzzle towards the target. A trade-off between speed and precision has to be made, accessories manufacturers being very keen in trying to reduce as much as possible weight, volume and, when applicable, power consumption.
The interface between the accessory and the rifle normally comes in the form of a rail, the most widely used type of interface being the Picatinny rail. By large the main accessory mounted on a rifle is the optical sight. In this article we will limit the analysis to day sights, as entering the imaging intensification and thermal imaging arena would need an article on its own.
The need for optical sights on standard assault rifles comes both from the need of higher accuracy as well as from the shorter barrels used on current weapons, which means that iron sights have a shorter base thus are less precise. Moreover, shooting in poor light conditions with iron sights is also a problem, as well as shooting against moving targets. The sight is typically positioned close to the CG at least longitudinally, and therefore its extra weight has a relatively limited effect on the trailing velocity.
Different types of sights are available, and although strict categorisation is always dangerous we should say that the two principal fields of use are aimed firing on medium distances and aiming at short and very short distances in urban warfighting. This said, some manufacturers try to provide soldiers with systems that attempt to operate properly in both situations. The number of aiming sight manufacturers is considerable; therefore it will be impossible to mention all of them. Although a few company names have become quite synonymous with assault rifle sights.
One of these is certainly Trijicon, whose fame comes from its Acog (Advanced Combat Optical Gunsight) family of parallax-free reflex sights, the reticles of which are illuminated by a fibre-optic light collector in daytime and by a tritium source at night, making them battery free. Acog sights are all magnified sights, however thanks to the Bindon Aiming Concept, named out of Trijicon founder Glyn Bindon, it is possible to employ them with both eyes open, ensuring maximum situational awareness to the warfighter.
Currently nine different models of Acog sights are available, with magnification of xl.5, x2, x3, x3.5, x4, x5.5 and x6 and different reticles, circle dot, dot, triangle chevron, donut, horseshoe and crosshair, depending on the model. The 4x32 Acog sight known as TA31RCO is the official US Army and US Marine Corps rifle combat optic, which features a chevron reticle with bullet drop compensator offering additional aiming points out to 800 metres.
All based upon an aluminium alloy housing and waterproof up to 100 metres, the weight of such optics varies considerably, the smallest models weighing 142 grams while the larger 6x48 TA648Doc weighs 1.05 kg, the standard issue TA31RCO weighs in at 330 grams.
However, the name Trijicon does not mean only Acog sights; recently the company developed the Tripower concept, which adds an on-call battery system which improves the reticle visibility under specific conditions. Moreover, when there is a need for perfect concealment, a rubber cover allows to obscure the fibre optics avoiding detection.
The company's Tripower model, the TX30, is a xl reflex sight with a red chevron reticle weighing 235 grams. It is waterproof up to 30 metres and operates on two 1/3N batteries. Trijicon also developed a series of Reflex sights for CQB, all at x1 magnification, which feature different types of reticle, mostly with dots but also chevron and triangle sighting. The RX01NSN model with a 4.5 MoA (Minute of Angle) dot was custom-designed for the M4A1 carbine and is provided to US Special Forces as part of Sopmod 1. With a weight between 120 and 345 grams (the SF model is at 261 grams) the Reflex series are considered primary sights.
To add a lighter option, one that can be used as a secondary sight, Trijicon developed the RMR (Ruggedized Miniature Reflex) series, with weights between 14 and 34 grams. These red dot reflex sights work on batteries (one CR 2032 lithium 3V) or on tritium and fibre optics, the battery solution ensures two years of continuous use at nominal temperatures and up to four years in dark storage. The RMR features a red LED reticle with a four or eight MoA option, while the tritium/fibre optic version has a 9 or 13 MoA dot. The lighter model features acrylic lenses with hard coating while the body is in glass-reinforced nylon polymer, the other three models, all but one unmagnified, feature glass lenses and forged aluminium cases.
For close-in shooting and patrolling, reflex sights are currently the prime choice. These normally allow the soldier to keep both eyes open, which helps to maintain a wide field of view and the maximum possible situational awareness. These sights are optical or computing sights that reflect a reticle image on a combining glass for superimposition on the target; they are most commonly available as non-magnifying sights.
The most widely used reflex collimator with red dot sights are probably those produced by Aimpoint of Sweden, which Comp family includes six models, all without magnification, parallax free, and with an LED eyesafe source operating at the 650-nm wavelength. According to the model the red dot diameter is 2 or 4 MoA (1 MoA = 1 inch at 100 yards or 30 mm at 100 metres), the sights have 4 to 7 settings for use with night vision devices and 6 to 9 for daylight operations, including one for extra-bright conditions.
Aimpoint M2 sights have a battery life (two L76 Lithium batteries) of around 10,000 hours at room temperature, while the M3, which uses the CET (Circuit Efficiency Technology) gives 50,000 hours, and the latest M4 with the Advanced CET operates for 80,000 hours with a single AA battery, those figures increasing by a factor of eight to ten when the sight is used at night.
The weight of such sights is limited, between 220 and 335 grams with mount, however Aimpoint decided to provide the warfighter with an even lighter sight, the Micro T-1, only 84 grams, which features the latest technologies and a smaller and lighter battery, the Lithium CR2032, which has a 50,000-hour lifespan.
Among best sellers of variable magnification sights is the Elcan Optical Technologies Specter range. The SpecterDR (Dual Role) l-4x Combat Sight, chosen by US Socom in 2007 as part of Sopmod 2 for enhancing the light weapons lethality, shifts from x1 to x4 magnification in less than one second, the field of view stepping from 26[degrees] to 6.5[degrees]. This gives the soldier the possibility to quickly adjust from CQB to long-range aimed firing, thereby adapting to the tactical situation.
Known as SU-230/PVS in US services, the sight is 153.1 mm long and weighs 640 grams. In CQB mode at x1 a 1.5 MoA 'both eyes open' red dot is provided, while at x4 a ballistic drop reticle is shown for precision engagement between 200 and 600 metres, a red dot and ranging mount are shown for machine gun use.
The SpecterDR features a back-up iron sight with front post and rear peep. Some 145,000 SpecterDRs were ordered by US Special Forces, the sight is in use with other services. Elcan proposes a variety of base designs that can be customised according to users needs. An extended-range version of the SpecterDR is also available, with a x1.5-6 magnification. It has 16[degrees] and 4[degrees] fields of view, is 184 mm long and weighs 700 grams. Both systems employ a DL1/3N 3V Lithium battery with an average operating time of 2000 hours.
The Elcan portfolio also includes the Lightweight Combat Optical Daysight, a fixed red dot x4 sight with a 6.5[degrees] FoV that has been selected for the UK Fist programme. At 528 grams without CQB mount and lens cover, it features a bright red spot with LED illumination for CQB and a ranged 5.56-mm reticle for accurate engagements at 400 to 800 metres. Two other fixed magnification sights are part of Elcan inventory, the SpecterOS 3x, with a 3.1 nominal magnification and a weight of 415 grams, and the SpecterOS x3.4, developed for the Canadian Army which names it C79; at a weight of 690 grams, it has an Elcan Post reticle with a tritium-illuminated horizontal stadia line which, according to the company, proved to be the fastest and more accurate targeting solution both during qualification and in battle.
Leupold, which last year launched its Leupold Tactical Optics division wholly dedicated to military products, has added to its long-range scopes a series of tactical sights for close quarter engagements. Its Prismatic rifle scope is a 1 x 14-mm tactical sight which adopts an etched glass reticle visible both with and without the illumination module, and that can be seen without batteries, in black colour. If the illumination module is fitted, eight brightness settings are available to illuminate the Circle Plex reticle. Windage and elevation in one-half-MoA adjustments are available, adjustment range being 70 MoA for both settings.
The sight is 114 mm long and weighs 340 grams, the main tube thickness makes it practically indestructible, according to the company, which also underlines how its field of view, 27.6 metres at 100 metres, is wider than that of most unmagnified red dot sights and allows for faster target acquisition. The rifle scope is designed to be used with both eyes open.
Among the new entries in Leupold inventory is the Deltapoint reflex sight, which can be used as a primary or add-on sight. It weighs in at only 18 grams thanks to its ultra-light rugged magnesium housing, and can be provided with two reticle options, 7.5 MoA Delta and 3.5 MoA Dot. The Deltapoint sight features an innovative aspheric lens, motion activation, auto-brightness sensor, locking elevation and windage adjustment system.
Besides unmagnified sights Leupold Tactical Optics proposes its Mark 4 CQ/T, a 1-3 x 14-mm scope that allows to shoot with both eyes open at x1 magnification while providing accurate firing at x2 or x3 magnification. The Arms Throw Lever Mount quick release allows sight installation and removal without loss of zero.
Carl Zeiss Optronics provides the standard optic of the G36 H&K assault rifle; the company's portfolio also includes the RSA-S unmagnified reflex sight featuring an automatic brightness adjustment system for adapting the red dot to the ambient brightness. The power to the LED illuminating the dot is provided by a silicon solar cell and a battery, the sight electronics ensure battery power consumption optimisation. The latest version is also NVG compatible.
The dot gives a 3.44 MoA while the FoV is only 10.6[degrees], which is compensated by the weight of 100 grams. Carl Zeiss also offers a x3 magnification adapter which slightly reduces the FoV to 8[degrees] and has a weight of 230 grams, which provides medium range aiming capacity. In March 2010 a licensing agreement was signed with Optic Electronic of India, which will produce red dot sights for that country. 10,000 sights having already been ordered from Carl Zeiss by the Indian Army while a potential market for 400,000 more sights is foreseen.
Carl Zeiss Optronics developed a 4x30 targeting optics with an 8[degrees] FoV, the reticle being provided according to customers request. The newest version has an illuminated rectangle as a reticle, which can be customised. The eye-to-eye-piece distance of 60 mm allows the Zeiss 4x30 to be used also on machine guns; its weight is 430 grams.
Burris, now part of Beretta, is proposing among its long-range rifle scopes, two variable magnification models for assault rifles known as XTR (Xtreme Tactical Riflescopes) respectively with x1-4 and x1.5-6 magnification, the first one intended for 5.56-mm calibre rifles while the second features a ballistic reticle for the 7.62-mm calibre. Both models can be used with two eyes open at minimum magnification, while the reticle is illuminated via a CR2032 battery. The two sights weigh respectively 482 and 540 grams.
Burris also supplies its AR-332, a 400-gram compact x3 prism sight, as well as its Fastfire II light red dot reflex sights, which may also be used as a secondary sight over the XTR models thanks to their sleight 45-gram weight. Powered by a CR2032 battery the high efficiency electronics and battery-save mode ensure a five-year lifetime. For use in severe scenarios Burris provides side metal wings that protect the sight from impacts. For shotguns a specific Speedbead system allows ultra-low mounting.
Meprolight of Israel chose tritium illumination to provide sights which do not need batteries or switches. Its Mepro 21 is a maintenance free, x1 red dot reflex sight with an aiming point illuminated by a fibre-optic collector in daylight and a tritium source at night. This sight was developed for the Israel Defense Force and allows rapid target acquisition as it can be used with both eyes open. The reticle can be chosen among a 5.5 MoA or 4.3 MoA aiming point, a triangle, a bullseye and an open 'X'. The Mepro 21 weighs 372 grams with the Picatinny adaptor.
Although the Mepro Mor retains most of the Mepro 21 characteristics, it lacks the 5.5 MoA dot. but includes a red and/or IR laser pointer, the first operating at 650 nm while the second has a wavelength of more than 830 nm. It can be used in fully passive mode, thanks to the fibre-optic and tritium sources, or as active reflex with an extra bright LED dot for specific conditions, power being provided by the batteries that also power the pointers.
The Mor is slightly larger and of course its weight is higher, 450 grams without adaptor and batteries. The Mepro MX3, a x3 magnifier, can be used with both sights, provides an 8[degrees] FoV and has a weight of 215 grams without an adaptor.
Another Israeli manufacturer involved in rifle sight production is ITL. Its portfolio includes two lines, the Mars family and the Raptor. The Mars (Multipurpose Aiming Reflex Sight) is a range of red dot reflex sights with auto brightness control that incorporates a single- or dual-wavelength laser pointer. All with a xl magnification, they are powered by one 1.5V AA or a 3.6-Volt lithium battery, which provides 200 continuous hours of operation and 10,000 laser illuminations of five seconds each. The weight without batteries is 400 grams. The Mars IR is equipped with a 0.4-mW laser operating at 850 nm, the Mars Visible Red has a 1-mW 650 nm aiming light, and the Mars Dual features both pointers.
The Raptor is a mini-reflex sight weighing less than 250 grams which features a hologram-like illuminated red aiming reticle with auto brightness control and automatic shut-off and motion activation. Also unmagnified, its single 1.5-Volt AA battery ensures two months operation, also thanks to the automatic power shut-off, which switches off the system when kept stationary for three to five minutes, reactivating it immediately when shifted. For both systems ITL developed the Trisight x3 telescope; without reticle, this system focuses from 50 metres to infinity and, at a weight of 185 grams, transforms the Mars and the Raptor into medium-range aiming sights.
L-3 EOTech is currently the only manufacturer using holographic technology for its sights; a hologram projects the image of a reticle onto the target plane. This allows a fully parallax-free reticle, while on other sights this is true only on the axis centre aim point. Holography requires a laser source, which creates an infinitely small dot, although this technology is more complex than that used in LED illuminated red dot sights. One of the few drawbacks is the higher energy consumption, which reduces battery duration, a major advantage being that the sight remains fully functional even if the glass is shattered or covered with debris, while other scopes are no longer functional if the glass is damaged. Currently the most widely used L-3 EOTech product in the military community is the 553.A65 sight which weighs about 350 grams, features a FoV of 28 metres at 90 metres, and has a 1100 hours duration on two 123 lithium batteries. This sight has been chosen by US Socom as part of the Sopmod 2 kit. However, L-3 EOTech further improved this product in terms of ergonomics and flexibility, with its latest model, the EXPS, which was launched last May. Compared to the previous model it has a shortened base, 70 mm vs. 100 mm, which saves space on the Picatinny rail; length reduction is mainly due to the adoption of a single 123 battery mounted transversally. A single quick release lever allows a return to zero repeatable within 2 MoA after the sight is back on the rail.
The weight is reduced to 317 grams, and all buttons have been moved to the sides for better accessibility. The EXPS is night vision compatible with a wide FoV. Ten brightness settings are available for night use with 20 for the daytime. Two types of reticles are available, a 65 MoA ring with a 1 MoA dot and a 65 MoA ring with two 1 MoA dots. According to the company, the ring allows the eye to acquire the image faster than any single dot or solid image while the 1 MoA dot in the centre of the reticle allows for precise shot placement. Battery duration is 600 hours of continuous use at nominal setting 12.
Aimpoint's CEU (Concealed Engagement Unit) which, when installed on company sights, allows one to observe and engage from a concealed or covered position. Developed by DSTO Australia under the name of Off-Axis Viewing Device, it is marketed by the Swedish company. The 135-grams CEU can rotate a full 260[degrees] and can be used with Aim-point's x3.
Aimpoint proposes its 840-nm LPI laser aiming device to be used with. Two power settings of 0.1 mW and 0.005 mW are available. Submersible to ten metres, the LPI is powered by a DL 1/3N battery, with which it weighs less than 130 grams.
Sights are definitely the most common accessories seen on assault rifles; however numerous other accessories such as laser pointers and tactical lights are also common add-ons. Here too it is impossible to mention all the manufacturers, as their number might be even greater than that of sight manufacturers.
In Europe, Rheinmetall developed a series of pointers and integrated illuminator/pointers that are produced with European-only components to avoid export concerns. Over 85,000 of its LLM-01 have been sold in the last five years. This module is fitted with a visible laser marker, an IR marker, an IR LED illuminator and a white lamp. The LLM-01 is a modular system for which the customer can chose the laser power, the visible between 0.4- and 20-mW and the IR between 0.7- and 35-mW, with either a laser diode or a focus-able laser illuminator up to 35 mW with an angle between 30 and 130 mills. The white light can be either a standard halogen xenon high-pressure lamp of 80 to 85 lumens or a LED light up to 180 lumens, the white lamp is exchangeable with an additional laser head.
Mode selection is done via a five-phase turn switch and a trigger cable is available for hand-on-rifle operation. The LLM-01 weighs less than 190 grams with batteries and can operate up to 60 hours depending on the battery type. Simpler versions are available, which are lighter (1.55 grams) and less expensive, such as the LLM-R with one laser, and the LLM-PI, which was developed in 2009. Two laser-only modules are also available, the LM-D with visible and IR markers and IR illuminator at 160 grams with a four-phase switch, and the LM-S visible or IR marker or IR illuminator at less than 100 grams. The LM-D has been provided among others to the Dutch Army to replace its AN/Peq-2A.
ITL of Israel has three short-range laser aiming lights, the Aim-1/C with IR source, the Aim-l/V with visible red dot marker and the Aim-2000 with dual capability. With a range up to 300 metres, the Aim-2000 features two output levels, high (five mW) and low (0.4 mW only in IR mode). Powered by AA alkaline batteries giving ten hours' continuous operating time, the weight of these attachments is around 200 grams.
As for tactical lights it is not possible to omit Surefire, whose current bestsellers are the Scout Lights, such as the M300A which packs 110 lumens for 1.3 hours in a mere 127 grams including the single 123A lithium battery and the tape switch. The company's M620C pushes out 200 lumens for two hours in a 179-gram package, the latter is available in white/IR light as the M620V, providing 150 lumens or 120 mW IR light for eight hours.
A Dingo for US Warfighters?
In mid-2010 the Darpa awarded two contracts for Phase 1 of a programme aimed at improving firing accuracy up to 600 metres. Known as the Dynamic Image Gunsight Optic system (Dingo), it will enable soldiers to accurately view targets at varying distances without changing scopes or suffering a decrease in optical resolution at ranges up to 600 metres while maintaining the capability to be used at very short distances. Two contracts have been issued; one worth $ 3.93 million was assigned to Lockheed Martin, while a second was given to Elcan. The Dingo programme will be carried out in three phases; Phase 1 to bring the technology demonstrator, Phase 2 to develop a brass board and Phase 3 expects a full prototype, which will then lead to production that has been forecasted for 2012.
The weight target for the Dingo is 250 grams without batteries. Lockheed Martin will exploit its experience acquired with the One Shot Advanced Sighting System, which provides soldiers with automatic crosswind data for long-range precision target engagement. Its system will leverage on recent breakthroughs in extremely high pixel-count cameras and in micro-displays, working on digital zooming for magnification while the integrated laser rangefinder will provide some wind information, although at a lesser sophistication level compared to the One Shot system in development. New camera technologies also provide good low light-level performances. Lockheed Martin has patented a Multi Gain Image Combination Process that allows a considerable reduction in bright points generated by light sources thanks to multiple image gating.
Elcon intends to leverage its Digitalhunter scope in developing a sight with a reticle and FoV that will automatically adjust for target range, wind and bullet ballistics. Optimised for hunting use, and with a x2.5-16.5 magnification provided by an electronic zoom, this all-digital sight features four different reticles and numerous electronic output interfaces. The Digitalhunter weighs 737 grams, but the Dingo will require a shorter optic due to the maximum range requirement, magnification limits have apparently not been specified by Darpa.