Machine-Guns.
Intermediate between hand-borne weapons and artillery, and partaking of the nature of both, come the machine-guns firing small projectiles with extraordinary rapidity.
Since the United States made trial of Dr. Gatling’s miniature battery in the Civil War (1862-1865), invention has been busy evolving more and more perfect types, till the most modern machine-gun is a marvel of ingenuity and effectiveness.
The Gatling machine-gun, which has been much improved in late years by the Accles system of “feed,” and is not yet completely out of date, consists of a circular series of ten barrels—each with its own lock—mounted on a central shaft and revolved by a suitable gear. The cartridges are successively fed by automatic actions into the barrels, and the hammers are so arranged that the entire operation of loading, closing the breech, firing and withdrawing the empty cartridge-cases (which is known as their “longitudinal reciprocating motion”) is carried on while the locks are kept in constant revolution, along with the barrels and breech, by means of a hand-crank. One man places a feed-case filled with cartridges into the hopper, another turns the crank. As the gun is rotated the cartridges drop one by one from the feed-cases into the grooves of the carrier, and its lock loads and fires each in turn. While the gun revolves further the lock, drawing back, extracts and drops the empty case; it is then ready for the next cartridge.
In action five cartridges are always going through some process of loading, while five empty shells are in different stages of ejection. The latest type, fitted with an electro-motor, will fire at the rate of one thousand rounds per minute, and eighty rounds have actually been fired within ten seconds! It is not, however, safe to work these machine-guns so fast, as the cartridges are apt to be occasionally pulled through unfired and then explode among the men’s legs. The automatic guns, on the contrary, as they only work by the explosion, are free from any risk of such accidents.
The feed-drums contain 104 cartridges, and can be replaced almost instantly. One drumful can be discharged in 5-1/4 seconds. The small-sized Gatling has a drum-feed of 400 cartridges in sixteen sections of twenty-five each passed up without interruption.
The gun is mounted for use so that it can be pointed at any angle, and through a wide lateral range, without moving the carriage.
The Gardner.—The Gatling, as originally made, was for a time superseded by the Gardner, which differed from it in having the barrels (four or fewer in number) fixed in the same horizontal plane. This was worked by a rotatory handle on the side of the gun. The cartridges slid down a feed-case in a column to the barrel, where they were fired by a spring acting on a hammer.
The Nordenfelt.—Mr. Nordenfelt’s machine-gun follows this precedent; its barrels—10, 5, 4, 2, or 1 in number—also being arranged horizontally in a strong, rigid frame. Each barrel has its own breech-plug, striker, spring, and extractor, and each fires independently of the rest, so that all are not out of action together. The gun has a swivelled mount easily elevated and trained, and the steel frames take up the force of the discharge. In rapid firing one gunner can work the firing-handle while another lays and alters the direction. The firing is operated by a lever working backwards and forwards by hand, and the gun can be discharged at the rate of 600 rounds per minute.
The Hotchkiss.—The Hotchkiss gun, or revolving cannon, is on a fresh system, that of intermittent rotation of the barrels without any rotation of breech or mechanism. There is only one loading piston, one spring striker, and one extractor for all the barrels. The shock of discharge is received against a massive fixed breech, which distributes it to the whole body.
Like the Nordenfelt, however, it can be dismounted and put together again without the need of tools. The above pattern throws 1 lb. projectiles.
The Maxim.—Differing from all these comes the Maxim gun, so much in evidence now with both land and sea service. It is made up of two portions:—
(1) Fixed: a barrel-casing, which is also a water-jacket, and breech-casing.
(2) Recoiling: a barrel and two side plates which carry lock and crank.
This recoiling portion works inside the fixed.
The gun is supplied with ammunition by a belt holding 250 cartridges passing through a feed-block on the top. Its mechanism is worked automatically; first by the explosion of the charge, which causes the barrel to recoil backwards and extends a strong spring which, on reasserting itself, carries it forwards again. The recoiling part moves back about an inch, and this recoil is utilised by bringing into play mechanism which extracts the empty cartridge-case, and on the spring carrying the barrel forward again moves a fresh one into position. Under the barrel casing is the ejector tube through which the empty cartridge-cases are ejected from the gun.
The rate of fire of the Maxim gun is 600 rounds per minute. Deliberate fire means about 70 rounds per minute; rapid fire will explode 450 rounds in the same time. As the barrel becomes very hot in use the barrel-casing contains seven pints of water to keep it cool. About 2000 rounds can be fired at short intervals; but in continuous firing the water boils after some 600 rounds, and needs replenishing after about 1000. A valved tube allows steam, but not water to escape.
The operator works this gun by pressing a firing-lever or button. After starting the machine he merely sits behind the shield, which protects him from the enemy, directing it, as it keeps on firing automatically so long as the bands of cartridges are supplied and a finger held on the trigger or button. By setting free a couple of levers with his left hand, and pressing his shoulder against the padded shoulder-piece, he is able to elevate or depress, or train the barrel horizontally, without in any way interfering with the hail of missiles.
We use two sizes, one with .45 bore for the Navy, which takes an all-lead bullet weighing 480 grains, and the other with .303 bore, the ordinary nickel-coated rifle bullet for the Army. But as the Maxim gun can be adapted to every rifle-calibre ammunition it is patronised by all governments.
The gun itself weighs 56 lbs., and is mounted for use in various ways: on a tripod, a field stand, or a field carriage with wheels. This carriage has sixteen boxes of ammunition, each containing a belt of 250 cartridges, making 4000 rounds altogether. Its total weight is about half a ton, so that it can be drawn by one horse, and it is built for the roughest cross-country work. A little machine, which can be fixed to the wheel, recharges the belts with cartridges by the working of a handle.
For ships the Maxim is usually mounted on the ordinary naval cone mount, or it can be clamped to the bulwark of the deck or the military “top” on the mast.
But there is a most ingenious form of parapet mounting, known as the garrison mount, which turns the Maxim into a “disappearing gun,” and can be used equally well for fortress walls or improvised entrenchments. The gun is placed over two little wheels on which it can be run along by means of a handle pushed behind in something the fashion of a lawn-mower. Arrived at its destination, the handle, which is really a rack, is turned downwards, and on twisting one of the wheels the gun climbs it by means of a pinion-cog till it points over the wall, to which hooks at the end of two projecting bars firmly fix it, the broadened end of the handle being held by its weight to the ground. It is locked while in use, but a few turns of the wheel cause it to sink out of sight in as many seconds.
The rifle-calibre guns may also be used as very light horse artillery to accompany cavalry by being mounted on a “galloping carriage” drawn by a couple of horses, and with two seats for the operators. The carriage conveys 3000 rounds, and the steel-plated seats turn up and form shields during action.
It is interesting to notice that an extra light form of the gun is made which may be carried strapped on an infantryman’s back and fired from a tripod. Two of these mounted on a double tricycle can be propelled at a good pace along a fairly level road, and the riders dismounting have, in a few moments, a valuable little battery at their disposal.
The Pom-pom, of which we have heard so much in the late war, is a large edition of the Maxim automatic system with some differences in the system. Its calibre is 1-1/2 inches. Instead of bullets it emits explosive shells 1 lb. in weight, fitted with percussion fuses which burst them into about twelve or fourteen pieces. The effective range is up to 2000 yards, and it will carry to 4000 yards. An improved Pom-pom recently brought out hurls a 1-1/4 lb. shell with effect at a mark 3000 yards away, and as far as 6000 yards before its energy is entirely exhausted. The muzzle velocity of this weapon is 2350 feet a second as against the 1800 feet of the older pattern. They both fire 300 rounds a minute.
The Colt automatic gun is an American invention whose automatic action is due to explosion of the charge, not to recoil. The force by which the motions of firing, extracting, and loading are performed is derived from the powder-gases, a portion of which—passing through a small vent in the muzzle—acts by means of a lever on the mechanism of the gun.
This is also in two parts: (a) barrel, attached to (b) breech-casing, in which gear for charging, firing, and ejecting is contained. The barrel, made of a strong alloy of nickel, has its cartridges fed in by means of belts coiled in boxes attached to the breech-casing, the boxes moving with the latter so that the movements of the gun do not affect it. These boxes contain 250 cartridges each and are easily replaced.
The feed-belt is inserted, and the lever thrown down and moved backward—once by hand—as far as it will go; this opens the breech and passes the first cartridge from the belt to the carrier. The lever is then released and the spring causes it to fly forward, close the vent, and transfer the cartridge from the carrier to the barrel, also compressing the mainspring and opening and closing the breech.
On pulling the trigger the shot is fired, and after the bullet has passed the little vent, but is not yet out of the muzzle, the force of the expanding gas, acting through the vent on the piston, sets a gas-lever in operation which acts on the breech mechanism, opens breech, ejects cartridge-case, and feeds another cartridge into the carrier. The gas-lever returning forces the cartridge home in the barrel and closes and locks the breech.
The hammer of the gun acts as the piston of an air-pump, forcing a strong jet of air into the chamber, and through the barrel, thus removing all unburnt powder, and thoroughly cleansing it. The metal employed is strong enough to resist the heaviest charge of nitro-powder, and the accuracy of its aim is not disturbed by the vibrations of rapid fire. It does not heat fast, so has no need of a water-jacket, any surplus heat being removed by a system of radiation.
The bore is made of any rifle calibre for any small-arm ammunition, and is fitted with a safety-lock. For our own pieces we use the Lee-Metford cartridges. Four hundred shots per minute can be fired.
The gun consists altogether of ninety-four pieces, but the working-pieces, i.e. those only which need be separated for cleaning, &c., when in the hands of the artilleryman, are less than twenty. It can be handled in action by one man, the operation resembling that of firing a pistol.
The machine weighs 40 lbs., and for use by cavalry or infantry can be mounted on the Dundonald Galloping Carriage. The ammunition-box, containing 2000 rounds ready for use, carries the gun on its upper side, and is mounted on a strong steel axle. A pole with a slotted end is inserted into a revolving funnel on the bend of the shaft, the limbering-up being completed by an automatic bolt and plug.
The gun-carriage itself is of steel, with hickory wheels and hickory and steel shafts, detachable at will. The simple harness suits any saddled cavalry horse, and the shafts work in sockets behind the rider’s legs. Its whole weight with full load of ammunition is under four hundredweight.