pawl 21 after returning barrel 10 with push piece 20 to the initial position while the piston is held at its intermediate position by engagement of retaining detent 15 with the first retaining recess 14 a first full lever movement of barrel 10 will displace piston 13 rearwards from its fully released position to the intermediate position and a second full movement will urge the piston back from the intermediate position to the fully cocked position for firing at full power when barrel 10 is returned to the normal in line 34 fire 34 position pawl 21 is retracted clear of piston 13 this arrangement halves the maximum cocking force which has to be applied to barrel 10 as the mechanical advantage of the lever system is doubled by using the two successive repeat movements of the barrel greater compactness of the lever mechanism is achieved as less travel is required per cocking stroke thus a much neater appearance is possible in the vicinity of the barrel fulcrum pivot 12 and the length of various components such as push piece 20 does not have to be so great nor does the groove in the cylinder wall have to be so long thus giving increased strength the intermediate position may be selected to give the required low power mode of operation for example if the low power is to be half the full power the piston travel in the low power mode may be more than half the total piston travel to compensate for the changing load of the spring.