Abstract: The invention relates to a device as well as a method of monitoring the movements of a breech-block of a firearm, in which the time duration of a sequence of cyclical movements of the breech-block is sensed to provide a like sequence of pulses. Each cyclical movement of the breech-block from and to a rest position provides a pulse of a width initiated upon the movement of the breech-block from the rest position and terminated upon the return movement of the breech-block to the rest position, each part movement corresponding to a bullet firing. The number, duration and time spacing between successive ones of the pulses is analysed to determine the nature of the firearm operation effected by at least one movement of the breech-block.