cartridge case is housed a propellant and an igniter composition for igniting the propellant a detailed description of the components of weapon 1 and their function is not essential to the understanding of the present invention and will therefore be omitted according to the present invention weapon 1 is provided with means for preventing firing of the round 3 loaded therein if the weapon is overheated for example due to the weapon being subjected to the heat from a fire these means consist in preferred embodiments of means for deforming the inner surface of the barrel or launch tube 4 so that the round 3 is unable to leave the barrel or launch tube even if the propellant in the cartridge 10 case is accidentally ignited due to overheating of the weapon 1 in the first embodiment the means for deforming the inner surface of the barrel or launch tube consist of a ring 2 of shape memory alloy sma surrounding the outer periphery of the barrel or launch tube 4 when this ring 2 reaches a certain temperature which should be lower than the temperature at which the propellant self ignites it will in a few seconds reduce its diameter and thereby also the diameter of the barrel or launch tube for the above mentioned weapon at4 weapon system the temperature at which the dimensional change of the ring 2 shall occur is about 100 u00b0 c a suitable sma for a temperature of about 100 u00b0 c is for example nitinol an alloy of approximately equal parts of ni and ti the ring 2 is manufactured by several operations of drawing and heating a strip of sma until the desired contractile property of the strip is obtained the strip.