An active part of an ammunition device. A casing is provided with a sleeve in association with an opening of the casing. A sprung device is arranged between a locking device arranged at the opening of the casing and the sleeve. The end of the sleeve facing away from the sprung device contacts an explosive charge arranged inside the casing of the active part or a liner arranged on the surface of the explosive charge which faces towards the sleeve and the locking device. The locking device is designed to be released from the casing by the action of a force. The active part keeps the active part intact even if materials in the active part have greatly varying coefficients of thermal expansion, while at the same time, in extreme temperatures, the active part is prevented from detonating by the locking device being released from the casing.