Abstract: An ejecting mechanism for an ammunition body is operated by pressurized gas from a high pressure bottle for pressurizing a double piston, which controls two ejectors through a hydraulic valve system. The pressurized gas is heated by a heater surrounding the high pressure bottle to keep the bottle and its content at a temperature that corresponds approximately to the highest outer temperature under which the ejector mechanism is expected to operate. Thus, the pressurized gas has the same energy content at all expected external operating temperatures. After an ammunition body has been ejected, the ejector pistons are pushed back again under an electrical control signal from a control which controls the valve system, whereby the hydraulic oil is pressed back into a hydraulic reservoir. The ejector pistons are of the stepped type to facilitate the intended operation.