On November 7, the British Army’s Ajax armored reconnaissance vehicle completed its manned firing trials with its turret, which utilizes the CT40 autocannon. While this may seem unremarkable on the surface, it marks another step towards the first real adoption of a gun using cased telescoped ammunition (CTA) technology, which has been in development since the 1950s. The technology was considered for many uses in the past, including for the M2 Bradley. But only recently has it reached technical maturity, and it is now being seen as a serious way to increase firepower in autocannons and infantry weapons.
Cased telescoped ammunition was invented in 1954 , in a U.S. Air Force laboratory. The idea is very simple: instead of having the projectile protruding outside of the cartridge, as in standard ammunition, CTA places the projectile inside the cartridge . In such a configuration, the projectile is considered to be “telescoped” inside the cartridge. When a CTA round is fired, a small booster charge pushes the telescoped projectile out of the casing. Once the projectile is in the barrel, the remaining propellant in the casing ignites, generating the pressure required to push the projectile down the barrel. The timing between the booster charge and the main propellant is critical for the CTA to work. CTA technology decreases the size of the ammunition and allows it to take the form of a simple cylinder, unlike other ammunition types, which are more complex. This allows for a decrease in weight, more compact ammunition, and smaller and less complex feeding mechanisms.
The first real serious project that attempted to incorporate CTA was in the 1990s. The twenty-five-millimeter Bushmaster cannon on the M2 Bradley began to be seen as inadequate against future Soviet AFV threats. A forty-five-millimeter cannon incorporating CTA technology was consequently developed. Rarefaction Wave gun technology was also tested on this forty-five-millimeter platform. The British MoD picked up on this development, as it was also looking to replace the thirty-millimeter RARDEN cannon that armed its own FV510 Warrior IFVs. Royal Ordnance and GIAT (a French armament company) produced their own forty-five-millimeter Cased Telescopic Weapon System in 1992 . This system could be mounted on both an upgraded FV510 Warrior and the new French VAD 8×8 project. However, due to defense cutbacks, this was not adopted, and both the French and British IFV modernization projects were canceled. Luckily, the cooperation between Royal Ordnance and GIAT in developing the forty-five-millimeter CTA gun lead them to form CTA International, a joint venture company , in 1994, to further develop and market the technology.
CTAI went on to produce a variety of turrets using the forty-millimeter CTA cannon module throughout the 2000s. One application for these turrets was Warrior modernization. In that realm, CTA turret designs competed with turret designs using traditional autocannons such as the thirty-millimeter Bushmaster Mk44. The British government hesitated to choose a turret throughout its involvement in Iraq. Finally, in 2015, the Ministry of Defense settled on a turret, signing a deal in 2015 , with 515 CT40 armed turrets being provided for the new Ajax reconnaissance vehicle and Warrior modernization projects. The CT40 cannon was also selected for use on France’s new wheeled reconnaissance vehicle, the Engin Blindé de Reconnaissance et de Combat Jaguar , on April 22, 2017. The system is also offered by Thales Defense as a new-generation antiair gun , firing programmable ammunition.
So how does CTA technology allow the CT40 cannon to perform above its competition? Due to the nature of telescoped ammunition, CTA ammunition has 30 percent more performance for the same volume of ammunition. This can be seen in a comparison of the size of the rounds: forty-millimeter CT ammunition is only the size of conventional thirty-millimeter ammunition while delivering performance on par with conventional forty-millimeter rounds. Talking in numbers, the forty-millimeter CT Armor Piercing round can pierce 150 millimeters of armor at 1.5 kilometers. This is sufficient performance to defeat any current BMP-series IFV and their upgrades. This is superior to the hundred-millimeter-plus RHA at one kilometer offered by the 30×173-millimeter rounds used by the latest versions of the U.S. Army’s thirty-millimeter Stryker . The airburst capability of the forty-millimeter CT rounds is also superior, more than doubling the affected area versus thirty-millimeter rounds. All of this comes in a package that is around the same size and bulk as the thirty-millimeter cannons. The CT40 cannon can also hold more rounds in the ready position, around a hundred ready rounds compared to the twenty-four to twenty-five ready rounds that are possible with the Swedish forty-millimeter L/70 cannon on the CV9040, as reported by Jane’s. This is due to a novel rotating breech that is deployed on the CT40 cannon, as well as a linkless ammunition-feeding mechanism , made possible by the geometry of the CTA rounds.
Despite its adoption, CTA technology has not been without its detractors. A 1996 Department of Defense Inspector General report into CTA systems found many flaws. CTA guns demonstrated higher levels of barrel wear and increased recoil, as well as problems clearing malfunctions such as hangfires. While the barrel-life problem has appeared to be addressed in the CT40 cannon ( ten thousand rounds cited in one report ), how the other factors are handled have yet to be seen in reports. However, the last criticism of the DoD IG report rings true: CTA guns and ammunition cost significantly more than conventional guns. Some inside the UK defense community have described the cost of ammunition for the CT40 gun as “eye-watering,” and begun to wonder if similar performance could not be achieved with a conventional autocannon design similar to the Russian fifty-seven-millimeter autocannons currently under development. The high cost is due to the novel nature of the ammunition being produced, which requires the establishment new ammunition manufacturing processes. For this to truly be addressed, Britain and France must adopt the CT40 in large numbers or make it a success in the export market, so that economies of scale can be established.
Charlie Gao studied political and computer science at Grinnell College and is a frequent commentator on defense and national-security issues.
Image: Wikimedia Commons / Sgt. 1st Class Johancharles Van Boers.