ABOVE: German 4.73x33mm HITP G11 caseless cartridge components (L-R): Plastic cap, projectile, booster cup, propellant body and primer (not visible). The propellant and primer are both combustible, while the plastic cap and booster cup are post-firing remnants, discarded from the muzzle.
Emergent Small-Caliber Cartridge Technologies: Current and Horizon Technology Trends
By N.R. Jenzen-Jones
Emergent ammunition technologies are likely to prove key in future firearms designs, with many also applying to legacy weapons. Polymer-cased ammunition, the rise of the so-called “intermediate” caliber and other technologies, will affect the way in which firearms are produced, issued, employed, maintained and resupplied. Many of these technologies are focused on reducing the logistics burden on militaries and reducing the carrying load of the individual soldier. While these technologies also apply to medium and large caliber ammunition, this report will restrict its focus to small caliber ammunition—cartridges of up to 14.5x114mm in caliber, commonly fired from small arms and some light weapons.
Polymer cartridge cases have the potential to significantly reduce the cost and weight of conventional ammunition. Several militaries and commercial groups have shown interest, and the technologies are rapidly advancing. Caseless ammunition seeks to obviate the need for cartridge cases entirely, instead embedding the projectile in a “block” of propellant. Caseless ammunition would also reduce weight, even more significantly, but presents several significant technological hurdles. Telescoping ammunition is another method of saving weight, while also reducing the overall volume of a round. This technology is being applied to both caseless and polymer-cased ammunition.
While the majority of current and horizon technologies relate to the cartridge case and/or cartridge configuration, the introduction of a ballistically superior general-purpose caliber—generally acknowledged to be in the 6.0 to 6.9mm range—has the potential to bridge the gap between 5.56×45 and 7.62x51mm cartridges in many modern militaries. Small caliber ammunition in this range would be applicable to a range of small arms. If such a caliber were to replace two or more in-service calibers, there exists the potential for significant savings in cost, a simplification of production and sustainment and advantages for interoperability of weapons systems and training.
Many of these emergent technologies are, or will be, compatible with one another, offering advanced synergies for the ammunition of tomorrow. An intermediate caliber could readily be made compatible with other emergent ammunition technologies, perhaps heralding the introduction, for example, of a polymer-cased, telescoping, intermediate caliber cartridge, marked using emergent marking technologies. Other emergent ammunition technologies, including advanced marking practices leveraging new technologies such as laser cartridge case marking and ballistic imprinting (“microstamping”), guided small caliber ammunition, and other ammunition advancements are not covered in this report.
Following are some of the most important aims and requirements of modern cartridge case design, in descending order of priority. Depending on the end user and intended use, some of these requirements may prove more or less important.
Reduce ammunition weight;
Reduce ammunition volume;
Increase the number of rounds that can be carried;
Improve hit probability;
Enable special applications;
Allow for the enhancement of legacy weapon systems and/or the development of new weapon systems;
Reduce ammunition cost (production & procurement);
Reduce ammunition transport costs; and
Improve general performance and function.
Emergent Cartridge Case Technologies
Polymer Cartridge Cases
Polymer cartridge cases face a number of design challenges. The material selected must be able to withstand the various mechanical, thermal and chemical stresses which cartridge cases are subjected to. The cases must be low-friction, feeding and loading in a weapon as a finished brass case would. Polymer cartridge cases used in existing weapon designs must be produced from a material with elastic properties matching that of brass, so as to allow for consistent obturation and extraction. Some manufacturers have claimed that their polymer materials obturate better than brass cases (Western Shooter, 2011). Consistency in manufacturing is essential, ensuring not only accuracy but also safety.
The primary advantage to polymer-cased ammunition is a reduction in overall cartridge weight. According to one manufacturer, pistol cartridges see typical weight reduction of 11.5% to 20%, while rifle caliber cartridges are 23% to 60% lighter (PolyCase, n.d.). Polymer cartridge cases typically require a thicker case wall when compared to brass, resulting in a slightly reduced cartridge case capacity. As a result, the amount or type of propellant used may vary from their brass counterparts.
Polymer-cased conventional ammunition is currently available from a small number of manufacturers. Other manufacturers have previously offered similar products or are intending to do so in future. Commercially successful designs, or those seeking widespread military acceptance, will need to function correctly in existing firearms designs. There have been issues with some currently-available ammunition using polymer cases, including reports of catastrophic failures (C., 2014). Some manufacturers of polymer cartridges have indicated that their ammunition should not be used in firearms with fluted chambers, such as the Heckler & Koch G3 series of rifles (PCP, n.d.).
The most successful designs of polymer cartridge case ammunition used with unmodified self-loading firearms employ metallic cartridge case heads. This is to provide sufficient strength to the thin rim of the case for the relatively violent extraction and ejection forces commonplace in the regular functioning of a firearm. Rim and base strength is critical when ensuring safe, reliable operation in firearms. This importance is even more pronounced with aged or fouled weapons. At least one manufacturer intends to offer cartridges with a metallic case rim only (PolyCase, 2015).
Cased telescoped ammunition
Emergent cased telescoped (CT) ammunition (sometimes referred to as “cased telescoped ammunition” or “cased telescoping ammunition,” and by the acronym “CTA”) offers a significant reduction in both weight and volume of the cartridge. In telescoped cases, the projectile is seated fully within the length of the cartridge case, reducing a cartridge’s overall length (see Image 4). This configuration also obviates the need for metal cartridge case heads while maintaining a functional level of case strength and integrity. A rim or extractor groove is typically not required, because the mechanism of the weapon forces the fired case forward using a rammer, rather than extracting it towards the rear as with most conventional firearms. The weapon mechanism must be purpose-built to allow for the use of cased telescoped ammunition, making it incompatible with conventional firearms and thus costly, requiring a complete replacement of both ammunition and weapons system.
Telescoped cartridge designs have been under development since the 1950s, using various materials including light metals, polymer and even some employing fully combustible caseless technology. Early iterations of telescoped ammunition were designed around medium caliber projectiles, including examples in 20, 30, 40 and 75mm configurations. Technological limitations meant that early CT cartridges were typically heavier and occupied more volume than their conventionally-configured counterparts, as well as suffering from ballistic inefficiencies (DoD, 1996).
Some successful employments of telescoped cased cartridge technology were developmental weapons, including the Heckler & Koch G11 caseless self-loading rifle and the Steyr candidate for the US Army’s Advanced Combat Rifle (ACR) program. (Both of these designs used telescoped fléchette ammunition.) (Johnston & Nelson, 2010).
Some specific technical challenges with telescoped case designs include controlling the “jump” of the projectile into the barrel, ensuring the correct orientation of ammunition when filling magazines and the proper sealing of the chamber in order to achieve correct function. The most significant effort examining CTA to date is the US Army’s Lightweight Small Arms Technologies (LSAT) programme (Shipley & Spiegel, 2005).
Currently, the greatest reduction in cartridge weight and volume can be achieved by the use of caseless (CL) ammunition. In this configuration, the cartridge body is comprised of the propellant, leaving no case to be discarded once fired. Certain iterations of this technology, using a 5.56mm projectile, have achieved a reduction in weight of nearly 50% as well as a 40% reduction in overall cartridge volume (Phillips, 2010). This can only be achieved with a significant increase in the complexity of the weapon system used to employ the ammunition, which imposes additional reliability challenges. As a result, there are no small arms in military service which use caseless ammunition, despite attempts to perfect these systems for more than seven decades (Schatz, 2015).
Caseless ammunition technology presents unique and significant technical challenges which need to be overcome before such ammunition would be viable for military use. The author assesses such adoption, under current and near-future technological constraints, to be highly unlikely.
Synergies of Emergent Ammunition Technologies
The likelihood of large-scale adoption of emergent ammunition technologies
Plans for a general-purpose caliber between the current 5.56x45mm and 7.62x51mm standards are most often challenged on the drawbacks of weight. That is, on average, the overall weight of ammunition would increase if the same number of rounds were to be carried by a unit or squad. While the adoption of a general-purpose caliber would no doubt provide the infantryman with a ballistically superior cartridge, the success of the concept hinges on whether or not this increase in capability is necessary and, more importantly, whether it is worth the trade-off in terms of weight. The weight reduction from advanced case technologies may neutralise this disadvantage and allow for greater performance to be built into smaller caliber cartridges, which could prove a key enabler for the adoption of a general-purpose caliber. As such, the viability of a widely-issued general-purpose caliber may well be tied to the success of programmes examining other emergent ammunition technologies, including polymer cartridge cases, advanced propellants and telescoped cartridge configurations.
The adoption of polymer-cased conventional ammunition, while likely to have a lesser economic and logistical impact than the introduction of either a general-purpose caliber or more radical changes in cartridge case technology, such as caseless or telescoped rounds, would still pose a significant economic and logistical challenge. Manufacturing plant and techniques would need to be replaced or adjusted at major manufacturing centres in order to produce such ammunition on a large scale. Existing polymer ammunition for army testing has been produced on a comparatively small scale and by alternative manufacturers to those traditionally producing cartridges and cartridge cases for military service (Hunt & Stoll, 2012). Given the significant impacts to the manufacturing process required by the introduction of any of the emergent ammunition technologies discussed herein, it is likely to prove substantially more cost-efficient to adopt a combination of technologies at the same time, if desired.
A new cartridge which requires a significant adjustment to production infrastructure or weapon systems will not be acquired and fielded unless it offers a substantial advantage over the current caliber mix, or unless such an acquisition is conducted in conjunction with the adoption of other new technology which requires the replacement of existing ammunition. Given past acquisition trends, it is highly improbable that NATO would adopt a new cartridge unless the US armed forces, and the US Army in particular, intends to field it in significant quantities (both the 5.56x45mm and the 7.62x51mm cartridge were developed for the US Army, before being adopted by NATO). As a result, US Army requirements are the most critical factor in determining whether a general-purpose caliber is likely to be adopted by major western militaries.
Any new family of small arms would not be anticipated to enter US service prior to 2025 (Williams, 2015b). As such, requirements for these systems are still being developed and are likely to draw on a number of programmes and studies, including those previously concluded, currently underway and yet to be undertaken.
(The horizon for emergent cartridge case technologies is outlined in Table 2 of ARES’ original paper, available at: www.smallarmssurvey.org/publications/by-type/reports.html.)
Polymer cartridge cases in a conventional configuration for the .50 BMG (12.7x99mm) caliber are expected to enter service in 2015, with other calibers to follow. Polymer cartridge cases in both CT and conventional configurations will be further developed over the next two to three years, with a general-purpose caliber CT cartridge expected in three to five years. Caseless ammunition technology, while remaining fraught with technical risk, should be viable for fielding in three to five years too, according to some analysts (Schatz, 2015b).
Perhaps the primary advantage of emergent cartridge case technologies are the weight and volume savings they offer. The most common perceived advantage of lighter weight cartridges is in reducing the immense combat loads regularly carried by the modern soldier. The direct, tactically-desirable result of this is increased mobility. This weight reduction, which ranges from some 15% to nearly 50% depending on the technology, could instead allow for soldiers to carry a significant amount of additional ammunition beyond their current-day standards, allowing for overall increased unit “firepower” (Phillips, 2012; Shipley, 2015).
With a polymer case, a soldier would be able to carry approximately 170 rounds of .264 USA (a conventional cartridge configuration) at the same weight as 210 rounds of brass cased 5.56x45mm M855A1. The .264 USA projectile loaded into a CT configuration is likely to be even lighter still and would confer notable overall length and volume reductions as well. Textron Systems’ belt-fed machine gun chambered for a CT cartridge with a .264 caliber projectile offers a 10% weight reduction over the existing US Army M249/M855 5.56x45mm combination and a 43% weight reduction over the M240B/M80 7.62x51mm combination.
Developments in cartridge technology over the past decade have been significant and have built on technologies developed in the 1950s and 1960s. Decades of unsuccessful and frequently costly attempts have led to emergent small caliber ammunition technologies which are ready, or nearing readiness, for large-scale adoption and field use. These significant technical advancements have been enabled by advanced polymer materials, combined with modern projectile and case modelling and design tools and assembly methods.
The next five to 10 years will prove critical for emergent ammunition technologies. Many of these have reached technological maturity already, while many others are expected to hit this milestone in the next two to five years. If a radical change from conventionally configured, brass cased ammunition is to occur on a large scale, it is likely to be led by the US Army and would be expected to occur in 2025 or beyond. It remains to be seen whether the advent of emergent small caliber ammunition technologies will result in a significant or sudden shift towards polymer cases or a general-purpose caliber or whether such advances will simply continue to drive the design and development of weapon systems incrementally forwards.
For references and bibliography, please see the original paper as presented in The Small Arms Survey. Available at: www.smallarmssurvey.org/publications/by-type/reports.html
The author is indebted to the late Jim Schatz, who was one of several key contributors to the original paper. His knowledge, wisdom and support will be missed. Special thanks are also due to Tony Williams, Sam Baartz, Jonathan Ferguson and Michael Smallwood, Federico Graziano, Nicolas Marsh, Beat Vogelsanger and several confidential sources.