Directly behind the barrels a carrier-block, _C_, is fastened to the shaft, and in its exterior surface semi-cylindrical channels are cut, which form trough-like extensions to the rear of the cartridge-chambers of the barrels, and are designed to receive and guide the cartridges while they are thrust into the barrels, and guide the empty cases while they are withdrawn. Behind the carrier-block the shaft carries, rigidly attached, the lock-cylinder, _L_, in which guide-grooves are formed, which are parallel to the barrels, and in which slide long breech-plugs or locks having a forward and backward motion of their own, and by which the cartridges are thrust into the barrels. They also close the barrels until after discharge, and then extract the cases. [Illustration: FIG. 88.] Each plug, or lock (Fig. 88), contains a spiral mainspring, _b_, acting on a firing-pin, _a_, by which the charge is fired, so that the plug performs all of the functions of a gun-lock, as well as of a breech-plug, _b′_ is the head of firing-pin (which engages in R, Fig. 89); _c_ is the lug for groove; _d_ is the hooked extractor which engages over the cartridge-head; and _e_ is the guide-rib for the lock. The lock is a rebounding one, the intention being that the firing-pin shall not project beyond the face of the block until, on being released from the cocking-piece, it flies forward and discharges the cartridge. The shaft, _S_, to which the group of barrels and both the carrier-block and the lock-cylinder are rigidly attached, is free to turn on its axis, the front end being journalled in the front part of the frame, and the rear end in a diaphragm in the breech-casing. The gearing by which the shaft is revolved consists of a toothed wheel, _G_ (Fig. 87), fastened to the shaft, and worked by an endless screw, _W_, on a small axle, _S′_, which passes transversely through the case at right angles to the shaft, and is furnished outside the case with a hand-crank, _K_. The crank may be worked from the side, or it may be attached to the rear end of the main shaft, giving in the first position a rapidity equal to about 800 shots per minute, and in the latter 1200 per minute. The rear end of the main shaft terminates in a screw, which is covered by a knob or cascable, which is turned when the crank is to be attached for rapid fire. The cartridge-carrier block is covered above the frame by a semi-cylindrical shell, which is provided at the top with an opening of suitable size and shape to permit a single cartridge to fall through it into one of the channels of the carrier-block, which it overlies. There is a trough extending upward from this opening and forming a hopper, in which feed-cases can be placed.