When the crank is rotated, it causes the shaft with the barrels, carrier-block, and lock-cylinder to rotate in the casing. The bolts, held by the guides in the surface of the lock-cylinder, also rotate with the barrels and other parts, but by the bearing of the bolt-lugs in the elliptical grooves in the barrel-casing the bolts on the right-hand side are forced to move forward, _dc_, towards the barrels, and those on the left to move backward _c′d′_. When each bolt in this rotation reaches the "loading-flat," a cartridge drops from the feed into the groove in the carrier-block, in front of the bolt. As the rotation continues the bolt pushes forward until, on reaching the "firing-flat," the cartridge has been completely inserted and the barrel closed. During this motion a groove on the right-hand side of the casing, _R_, catches the head of the firing-pin and retains it, thus compressing the spiral mainspring and cocking the firing-pin. A continuation of the rotation causes the firing-pin to pass out of this groove; and the action of the mainspring drives the pin forward and fires the cartridge. The motion continuing, the bolt is withdrawn by the left-hand groove, _c′d′_, and as it moves backward the empty case is drawn out by the extractor on the bolt. THE FEED. =The Bruce Feed= (Fig. 90).--This is a gravity feed consisting of an upright bronze standard, _a_, having two grooves in it. Below the grooves is a fixed mouth, _c_, and below this a wheel, _d_, having its axis to one side of the mouth and turning freely on this axis. When in use, the feed is inserted in an opening in the barrel-casing directly over the carrier-block, _e_. The paper box containing the cartridges (the top being removed) is placed in the fixed standard with the _heads of the cartridges to the rear_. The heads engage in the grooves of the swinging-piece, _b_, and the paper box may then be pulled off. As each cartridge strikes the wheel it causes the latter to revolve and present a new groove for the reception of a cartridge. The cartridges delivered to the wheel are in turn carried around by it and deposited in the grooves of the carrier-block. [Illustration: FIG. 90.] The cartridges in one column of the feed becoming exhausted, the weight of those in the other column causes the swinging-piece to rotate sufficiently for them to be fed to the piece.