THE GATLING GUN.
Fig. 86.
The following description applies more particularly to the model of 1883, which differs in some of its details from previous models. The 1-inch and .45-inch calibres are now in service; and contracts have been made for supplying .30-inch calibre.
The Gatling gun consists of a number of breech-loading rifled barrels, B, grouped around a shaft, S, to which they are parallel. The 1-inch has six barrels; smaller calibres eight and ten.
Each barrel is fired only once in the revolution of the group.
Fig. 87.
The breech-ends of the barrels are screwed into a disk or rear barrel-plate, P′, which is fastened to the shaft, and the muzzles pass through another similar disk, P, called the front barrel-plate, on the shaft; the shaft projects beyond the muzzles, and extends backwards for some distance behind the breeches of the barrels.
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to receive and guide the cartridges while they are thrust into the barrels, and guide the empty cases while they are withdrawn.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.
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.
Beneath the carrier-block everything is open, to allow the cartridges or shells which are withdrawn by the extractors from the barrels to fall to the ground. Within the cylindrical breech-case attached to the frame a heavy ring, not quite the length of the lock-cylinder, is fastened to the case and diaphragm, which nearly fills the space between the inside of the case and the cylinder. Portions of the inside of this ring are so cut away as to leave a cam projecting from the inner surface of the ring, having two helicoidal edges inclined to each other, and united by a short, flat plane. Against these edges the rear ends of the locks continually bear, there being room enough for the locks to lie loosely within the parts of the ring which are cut away. Each lock is held back against the cam by a lug projecting laterally from the end of the lock, and entering a groove formed at the base of the cam, in the thin part of the ring. A device for throwing the cocking-piece in and out of gear, worked by a knob on the right of the breech-casing, permits the gun being used for drill purposes without snapping the locks. When the arrow-head points to the front, it is in position for firing. With the head pointing to the rear it is out of action.
On the left of the breech-casing, just under the hopper, is a movable section with three wedge-shaped prongs, which keep the cartridge-cases in the grooves of the carrier until they are ejected. It is called the shell-guide.
The gun can be unloaded of any cartridges not fired by removing the feed-case, opening the hopper, and reversing the motion of the crank.
The locks can be removed and inserted without taking off the cascable-plate; and the absence of one or more plugs does not affect the working of the gun, except to diminish the intensity of the fire. For each lock removed one unexploded cartridge falls to the ground at each revolution of the gun.
The gun is encased in a frame which has trunnions, and is mounted in the ordinary way, like a field-piece.
The screw for elevating and depressing the breech works in a nut attached to the trail of the carriage in the usual way. In the model of 1883 the trunnions of the gun are placed two inches below its centre, and the elevation and depression are given by means of an arc connected at both extremities with the gun, which may be elevated 74° or depressed 78°.
A lateral movement is given the gun by means of a hand-lever which fits into a square mortise cast on the under side of the breech-casing.
On top of the breech-casing is a spirit-level placed parallel to the axis of the piece, and on the right side of the cascable-plate is another at right angles to the first.
Fig. 89.
ACTION OF THE MECHANISM.
In [Fig. 89] cd, c′d′ are the developments of the right-and left-hand sides of the elliptical groove; cc′ and dd′ are developments of the circular arcs.
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.
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.
The Accles Feed ([Fig. 91]) consists of a brass drum the distance between whose heads slightly exceeds the length of the cartridge to be used. The inside of the head is grooved in a spiral form ending at the mouth of the drum. The central part of the spiral is removed and replaced by the axis of a set of radial arms which rotate about this axis. The cartridges are inserted through the mouth of the drum into the spirals with the heads to the rear. When in use, the drum, a, is placed in position, with its mouth, c, down and over the grooves in the carrier-block, d. Projections, e, on the outer edges of the grooves in the block engage in the outer extremities, f, of the radial arms, b, of the drum so as to cause the latter to rotate when the crank is turned; and the arms, bearing against the cartridges, force them along the spirals towards the opening in the drum, whence they are delivered to the grooves in the carrier-block.
Fig. 91.
The Latest Improved Feed ([Fig. 93]) has but a small surface exposed to fire, is cheap, light, and independent of gravity, so that it may be used at any angle.
Long strips ([Fig. 92]) of tin or any cheap flexible metal have tongues, a, punched in them, one end of the tongue being left attached to the strip and the other separated. These tongues surround the cartridge and hold it in place on the strip. The small rectangular slots, b, are punched completely through, and in these slots fit the rims of the cartridge-cases.
Fig. 92.
Fig. 93.
A hopper (a, [Fig. 93]) is hinged to the frame which supports the gun just over the carrier-block, and has in it an opening, b, through which the strips, with the cartridges down, are fed. This opening is narrow in front and wide in rear to prevent the cartridge being introduced wrong end to the front. Below the opening, b, is a shelf, c, so shaped as to guide the cartridges and strips into the opening. Above the shelf is a flat spring, d, which presses the cartridges down as they pass through the opening.
A wedge, e, projects from the opposite side of the hopper, and, acting on each cartridge in turn, forces it out of the strip, the tongues, a, bending downward into the recess provided for them. The carrier-block, f, is provided with projections which act like the teeth of a wheel upon the cartridges, forcing the strip to the right.
When in use, a strip containing cartridges is pushed into the opening, b, of the hopper. The crank is rotated and the strip is forced to the right through the hopper. This action brings each cartridge in succession against the point of the wedge, e, which forces the cartridge out of its hold on the strip by bending downward the tongues, a, and the cartridge is deposited in the groove of the carrier-block, the empty strip passing to the right.
Before Firing the Gun.—The following points should be attended to:
The adjuster-nut should be at its proper position, viz., with the marks in line with each other.
The safety-cam (cocking-switch) should be set to fire arrow-head on knob pointing forward.
The shell-guide should be in its place and the hopper locked down.
Never turn the crank quickly while the lock-plug is out.
See that the safety-cam is turned out of firing position when the gun is being worked without cartridges.
Precautions to be Observed.—(a) Never lay the cover upon the ground, as it is liable to pick up sand and dirt, which may derange the working of the parts.
(b) A partially filled feed-case should not be put back into the ammunition-chest without being filled up, as the cartridges may become inverted and jam the gun.
(c) If the gun jams, remove the feed-case at once, open the hopper, and reverse the crank until all the cartridges are taken out. This will be found to save time, unless the cause of the jamming is evident and in the immediate vicinity of the hopper.
(d) See that all the parts are kept well oiled to prevent friction and scouring.
THE CARRIAGE, MODEL 1883.
The carriage is made of metal; the axle of steel without any axle-body; the wheels are of the Archibald pattern; and the trail of two plates of mild steel, reinforced on top and connected by five transoms. A gunner's seat is hinged to the top of the trail. The oscillating-lever, when not in use, is carried between the trail-plates. The elevating-arc is held in place by a binding-screw, and is worked by a bronze handle.
The field of oscillation is limited by two stop-pins in front of the swivel. They permit of about 50° of lateral movement, and the gun can be held at any point of this arc by a binding-screw, the handle of which is on the left cheek.
On each side of the gun, and fastened to the axle, is an ammunition-chest of steel for carrying feed-drums and certain tools. These chests are lined with wood, and running through the middle, separating the compartments for feed-drums, are blocks of wood with recesses in their tops for the following tools:
| Left Chest. | Right Chest. |
| 1 cam-extractor. | 1 crank-handle for gun. |
| 1 riveting-hammer. | 1 drift. |
| 1 oil-can. | 1 lock screw-driver. |
| 1 screw-wrench. | 1 T screw-driver. |
| 1 sight, left. | 1 pin-wrench. |
| 1 sight, right. |
The lids of these chests are fastened with hasps and turnbuckles. They can be locked with the ordinary padlock. A wiping-rod of brass is fastened to the under side of the stock.
THE LIMBER.
The limber is principally of metal. The axle and wheels are the same as in the carriage.
The limber-chest and lid are of Bessemer steel reinforced by angle-irons. The interior of the chest is divided by steel plates into three compartments for carrying ammunition. The centre one is subdivided by wooden partitions for carrying feed-drums.
The lid is fastened in the same manner as those on the axle-chests.
The following is the capacity of the limber-chest:
| Right and left compartments, 132 packages, each of 20 cartridges | 5280 | cartridges | |
| 4 feed-drums of 104 cartridges each | 416 | " | |
| Front centre compartment, 38 packages of 20 cartridges each | 760 | " | |
| These with the four feed-drums in the axle-chest | 416 | " | |
| Would give | 6872 | " | |
| Weight of piece | 237 | lbs. | |
| Weight of gun-carriage with chest and tools, without feed-cylinders | 594 | " | |
| Weight of limber and chest | 754 | " | |
| Weight of ammunition and chest | 230 | " | |
| Weight of one wheel | 106 | " | |
| Weight of feed-cylinder (filled) | 24½ | " | |