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_The Gardner._--The Gatling, as originally made, was for a time superseded by the _Gardner_, which differed from it in having the barrels (four or fewer in number) fixed in the same horizontal plane.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.