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Increasing performance of an armament system often leads to increasing the maximal pressure inside the chamber or increasing the compacity of the system. Telescoped ammunition and the associated weapon (40 CTAS) developed by CTA International is a solution that combines both improvements. With the increase of maximal pressure, the equations of interior ballistics might not be appropriate anymore since the models were established when the pressure was moderated. The aim of this paper is to compare the potential candidates for the equation of state of the combustion gases in a high-pressure system, such as telescoped ammunition. Within this study, the following equations of state are studied: ideal gas equation, Noble-Abel equation, Van der Waals equation and virial equation. The study is divided in two: a first study for air as the coefficients needed are easily accessible in the literature and a second study for combustion products stemming from propellant combustion.

Cased telescoped ammunition and associated cannon is a proven disruptive technology in medium calibre weapons, allowing increased lethality in a compact, multi role weapon system. From new ammunition development to support of serial production, an internal ballistics model is key to highlight design margins, support design improvement and performance increase. The architecture of the cannon and the ammunition result in a very specific internal ballistics mechanism which makes standard models unsuitable. This paper will detail the different steps of the internal ballistics cycle of the 40 mm cased telescoped ammunition and explain how each steps were studied from both theoretical and experimental point of view and aggregated to achieve the internal ballistics model of the CT cartridge.