Lightweight Small Arms Technologies

Lightweight Small Arms Technologies

The Lightweight Small Arms Technologies (LSAT) program is funded by the Joint Service Small Arms Program, with the goal of significantly reducing the weight of small arms and their ammunition. [] ] Following a series of military programs to investigate advances in small arms (the SPIW program, the Future Rifle Program, the ACR program, and the OICW program), the LSAT program is the US Military's latest project to replace existing US small arms. Tactical concepts and the research from the previous small arms programs indicates that lightening small arms is the only significant first step in small arms design towards increasing soldiers' lethality and survivability.

Initiated in 2004, development is now made by a team of eight companies led by AAI Corporation. Development began with the two types of weight reducing ammunition, and a light machine gun to serve as a testbed and technology demonstrator [] ] . Use of an LMG for this purpose is notable, considering its greater technical complexity than infantry rifles. Minimization of program risk is shown by the development of the lower performing but less risky polymer-cased ammunition alongside caseless ammunition (which falls higher in both criteria), by the use of extensive computer simulations before prototyping, and by the use of existing and proven technologies, such as the HITP (High Ignition Temperature Propellant)—developed for Heckler & Koch's G11.

As of 2008, the program has achieved tremendous progress, with already operational prototypes for the polymer-cased ammunition and the LMG that fires it. The less orthodox caseless ammunition is less than a year behind, and the design of a rifle firing both types of ammunition has already begun. The designers project further developments. These include improved projectile technologies, such as greener bullets and a more lethal calibre, as well as the use of electronics, such as rounds counters, and lasers for sighting, target acquisition, and steering [] ] . After further research and development into both ammunition types and the platforms that fire them, one of the two shall be chosen for production.

Program origin

The Lightweight Small Arms Technologies program is the culmination of much research and information obtained by the US Army. It succeeds several other programs to develop new small arms technologies, each program of which produced results that were infeasible or insignificant. The first three (the SPIW, the Future Rifle Program, and the ACR program demonstrated the ballistic problems of flechette ammunition, and the ACR program also showed the inability of kinetic-energy firearms to significantly compensate for human inaccuracy (the small accuracy increase of all of the concepts tested was out-weighed by the trade-offs required). The subsequent identification of programmable air-bursting munitions as the only way to significantly increase accuracy was followed by the fourth, and most recent, cancelled program—the OICW program. The ability to detonate an explosive in the air at range provided a huge increase in accuracy, but the resultant XM29 proved too heavy to use. The separation of the XM29 into the XM25 and the XM8 provided no long-term solution to the weight problem. For the program to be recovered (and the accuracy benefits to be used), the weight of infantry weapons needs to be reduced. Along with this discovery, other research also indicated the benefits of lighter infantry weapons. Existing heavy equipment may make other potential weapons and equipment (such as explosives) too much for a soldier to carry. The weapon and ammunition an infantryman has to carry each contributes more to weight than any other piece of equipment, and this affects a soldier and his team when it comes to mobility, responsiveness, carrying capacity, endurance, and supply lines. Concepts of future tactical scenarios envisage the remote aerial deployment of fast, well-equipped soldiers to quickly counter threats [] ] ; the logistics and mobility problems of heavy equipment hinder these possibilities. The LSAT program was necessary to lighten soldier's carrying loads and to make more sophisticated weaponry feasible.

The existence of weight-reducing technologies made the LSAT program feasible, and many of these technologies can be seen in the program's products. The lightest existing ammunition to fire standard bullets comprised caseless varieties. The Heckler & Koch G11 was the only weapon to achieve a service capable assault rifle firing caseless ammunition. Its unique ammunition, designed by Dynamit Nobel, introduced several important innovations, such as improved internal ballistics through the use of a primer, and the prevention of cooking off (the lack of a case makes it easier for a hot chamber to ignite the exposed propellant) through the use of the less sensitive hexogen/octogen as the explosive component. The Advanced Combat Rifle experimental program gave the US Army access to the ammunition and entrenched the ammunition as a viable option. With the high efficiency and lethality of the ammunition, the vast expenditure such a concept had needed for development, and the reduced risk of using an already proven ammunition design, the LSAT program chose a licensed version of Dynamit Nobel's caseless ammunition as a route towards its goal of weight reduction. The LSAT program also uses the same concept of a rotating chamber as the G11 (albeit, the LSAT LMG chamber swings around a longitudinal pivot [ Microsoft PowerPoint - Spiegel.ppt ] ]] , whereas the G11 chamber rotated around a horizontal axis at its very centre) [ [ HKPRO: The G11 ] ] .

Polymer casing for ammunition had already been developed and produced [ [ Microsoft PowerPoint - NDIA Presentation 051705.ppt ] ] , and it provided the second route for achieving weight reduction. While a polymer case could never be quite as light as no case, the risks involved in the use of polymer ammunition were less, due to its similarity to present ammunition and the reduced heat load on both the weapon and the ammunition's propellant.

Further budding technologies, such as alternative barrel materials (such as ceramics), and the increased efficiency and size reduction of telescoped ammunition (used by the G11 and other developmental weapons), also formed the basis for the LSAT program.

Program approach

The program itself uses a 'clean slate' design and had no requirements imposed on abiding by contemporary ammunition and weapon standards. Despite this, the program is using the M855 5.56x45mm round to provide comparison with existing weapons. The program has listed scalability of the ammunition calibre as a requirement, and its pursuit of a very light company machine gun would require a larger round. Therefore, the program seems set towards a more accurate, harder-hitting round (such as the 6.5 mm Grendel or 6.8mm Remington SPC).

The program has set itself weight reduction goals over the existing M249 and its ammunition of 35% for the weapon and 40% for the ammunition. Further goals to improve battlefield effectiveness have also been set: improved lethality; improved controllability (through recoil reduction, etc.); improved ergonomics; improved reliability and maintainability; integration of electronics; and equivalent cost and producibility to the existing weapon and ammunition. [ Lightweight Small Arms Technologies presentation at NDIA 2008] ]

In accordance with the program's name, the focus is on creating lightweight technologies for all small arms, and the Light Machine Gun it has started with is an entry point for a family of lightweight small arms and ammunition. Beginning with an LMG is unusual for an effort to develop a new family of weapons, although the increased engineering difficulty of a machine gun over a rifle is balanced against decreased attention and antagonistic scrutiny. The program minimized development risk: it used G11 technology that had been on the verge of deployment; and the parallel development of the composite-cased and caseless ammunition meant that, if the caseless ammunition effort succeeded, much of the development work gained with the composite cased weapon could be applied to it, and, if it failed, the composite-cased version was likely to succeed on its own [ Microsoft PowerPoint - LSAT NDIA Small Arms May 2006 ver2.ppt ] ] . This parallel development involves using what is essentially the same weapon for both types of ammunition, with the same action (having only marginal differences, such as added chamber sealing technologies required for the caseless firing version) and the same weight-lowering technologies.

For development, the program uses extensive computer simulation and modelling, particularly of the weapon action. This reduces both time and expenditure for prototyping and testing. The program also uses a 'spiral development' approach, whereby the weapon and ammunition is rolled out in stages or 'spirals', each stage producing a new version that is an improvement on those from previous spirals. A competition down-selected the design concepts of various companies to leave an AAI Corporation-led team of companies as the developers of the weapon system. The cohesive team of companies is combined with government support to ensure success.

Program Achievements

By 2008, the program had made tremendous progress, with all of its goals either fully achieved or with strong potential for achievement.

Light Machine Gun

The LMGs built made a 44% and 43% reduction of weight (for the cased telescoped and the caseless weapons, respectively). Secondary goals have also been met: the LMG has the potential to improve battlefield effectiveness (due to its simpler and more consistent weapon action, its light weight and low recoil, and its stiffer barrel); its use of recoil compensation (with a long-stroke gas-system, for example) has produced positive feedback regarding controllability; the simpler mechanism of the LMG is both more reliable and easier to maintain; a rounds counter has been integrated to improve maintainability, and the weapon is capable of accepting other electronic devices; improved materials used in the chamber and barrel have reduced heat load on the weapon; and the weapon cost is equivalent to the existing M249.

The LMG design is a traditionally (non-bullpup) laid-out machine-gun. It has many of the capabilities of other light machine guns, such as a quick-change barrel, a vented fore-grip, belt-fed ammunition, an ammunition pouch, and a roughly 600 rpm rate of fire. New features include the unique weight, a rounds counter, and a highly stiff and heat resistant barrel achieved with fluting and special materials [ [] ] [ [ Lightweight High Performance Gun Barrels] ] . Possibly the most radical part is its firing action: the weapon uses a swinging chamber. The chamber swings around a longitudinal pivot; it swings from horizontally parallel with the pivot (the firing position), to vertically parallel (the feed position), and back again. A long-stroke gas-piston is used to operate this action. A round is fed into the chamber at the feed position using a rammer, and the new round also serves to push a spent or dud round out of the far end of the chamber. Such rounds are pushed forward, parallel to the barrel, and they slide into a separate mechanism that ejects them out of one side of the gun. The advantages of this whole action include its simplicity, its isolation of the chamber from barrel heat, and its positive control of round movement from extraction to ejection. In the caseless firing version of the weapon, another mechanism is introduced to seal the chamber during firing (which is why the caseless weapon is roughly 1% heavier).


The cylindrical shape of the ammunition is crucial to the weapon's straight-through feed-and-ejection system, and it is the similar shape of the cased-telescoped ammunition to the caseless-telescoped ammunition that allows the parallel development of the two weapon systems. Telescoped ammunition's most notable benefits include the greater propulsive effectiveness of a telescoped round over standard ammunition, and the shorter feed and action times allowed by the shorter length of a telescoped round (both the cased and caseless designs are roughly 30% shorter).

Cased Ammunition

The cased ammunition is more advanced in development, partially due to the fewer technical difficulties and the fewer differences with standard ammunition. It has already reached the required technology readiness level of 5. As of 2008, the cased ammunition has been tested for a wide range of operating temperatures, and it has had over 9000 rounds fired (approximately 6500 rounds of Spiral 1 ammunition, and over 2000 of Spiral 2). The second spiral version of the cased ammunition produced a 33% weight reduction (falling just short of the program goal), while the ongoing development of the third spiral of cased ammunition has achieved a roughly 40% reduction. The third spiral is also 30% smaller than standard ammunition. The improvement by the third spiral of cased ammunition over the second spiral was achieved partially by compacting and consolidating the propellant (thereby allowing a smaller cartridge case and round). Having reached a sufficient technology readiness level, the Spiral 2 ammunition is being prepared for a contracted 2000 round delivery. The cased ammunition has shown itself as a virtually risk free option, with present and potential ability grounded in success. In addition, development of the cased ammunition firing weapon has significantly improved understanding of the weapon action and requirements.

Caseless ammunition

Although less advanced in development, the caseless round has already produced its own outstanding results. Having replicated Dynamit Nobel's ACR ammunition, the HITP (High Ignition Temperature Propellant—it is hexogen/octogen based to decrease heat sensitivity) based ammunition was modified to a 5.56 mm round. Tests proved the ammunition's usability, and development of the weapon was advanced using knowledge gained from the cased ammunition version. The Alliant Techsystems ammunition production team has reduced the production time and costs by reducing from fourteen to two the number of steps used to complete processing. The second spiral of caseless ammunition was rolled out in 2008, with the necessary facilities to produce the ammunition in bulk completed. It has vastly reduced the weight and volume of standard ammunition (by 51% and 40%, respectively), and it has reached the verge of achieving Technology Readiness Level 5. The development of the third spiral was also initiated, with the goal of replacing the propellant binder with a binder more environmentally and cost friendly. It also aims to reduce the heat ablation on the inside of the weapon by modifying the burn rate of the propellant, and by giving the round an exterior coating to absorb or prevent transferred heat. Benefits the system has gained from using the caseless ammunition go beyond the unparalleled weight and volume reduction to, for example, the lack of ejected shells (which both improves the weapon's protection from dirt and removes any need to 'police' cases after firing).

Assault rifle

Design of an LSAT battle rifle began in 2008. Half way into 2008, the designs are nearing completion. The rifle designs are made to use the same cartridge as developed for the LMG, and this means separate rifles are being designed for the cased and caseless cartridges. Design began with seventeen concepts; after the concepts were investigated and trade-offs were analysed, only two remained for the cased round, and two for the caseless round. The concepts involve two magazine approaches, both of which are focussed on high capacity: one uses the standard approach of placing inside the magazine springs that feed rounds into the weapon; the other uses a 'weapon powered' approach, presumably to reduce the extra weight and space that springs create in magazines. If any of the rifle designs use the same swinging chamber mechanism as the LMG, they should be well suited to a bullpup layout, since the forward ejection of the push-through feed-and-ejection mechanism could easily be extended to achieve full ambidexterity [] , which is a problematic absence in most bullpups. Even in other configurations, the push-through mechanism lends itself very well to ambidexterity: the G11 demonstrates this. The rifle designs are undergoing the same simulated, structural, and kinematic analyses as the LMG.


See also

* MR-C
* Heckler & Koch G11
* Future Force Warrior
* Future Combat Systems

External links

* [ Presentation by Kori Spiegel.]
* [ Brochure by AAI.]
* [ 2007 National Defense Industry Association conference.]
* [ Background of the program.]
* [ Composite casings.]
* [ Defense Review.]
* [ Defense Update.]

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