The 19th Century saw a proliferation of hand operated machine guns, that was kicked off by the success of the Gatling Gun. In the beginning, the Nordenfelt gun had 4 to 10 barrels operated by a crank on the right side, using back and forth motion as opposed to the Gatlings rotary handle. Invented and built by the Swedes, the British Navy adopted it in the 1870's, mainly in calibers as large as 25mm for use against the new torpedo boat threat.
However, in rifle calibers, the gun can keep up a semblance of automatic fire by how quickly the handle is operated and the ammunition kept supplied. In a test by the British, the gun demonstrated 3000 rounds a minute with no stoppages. During the Sudan War in the 1880s, the Nordenfelt was mounted on General Gordons Nile riverboat fleet, to good effect. In the end the Maxim gun replaced this, as well as the Gatlings in British service, when the Nordenfelt Guns and Ammunition Company was absorbed by Hiram Maxim in 1888.
The Nordenfelt was fielded by the British navy to counter the new torpedo boats, which were quickly spreading to all navies in the late 1870's. A small fast steam powered boat loaded with torpedo's could take down a capital ship, and losing some of these cheap boats in the attempt would pose little loss for the user. In the end, the defense against the torpedo boat became a new class of fast fighting ship, the destroyer.
The Nordenfelt gun was shown in the movie "Khartoum", starring Charleston Heston as General Gordon, and is seen used by Egyptian troops on river boats engaging the dervishes. With the British unable to reach Gordon in time, the Mahdi has his head.
Video from the Friends of the Cerberus
The single barrel Nordenfelt gun. The more interesting of the Nordenfelt guns was one that was ignored by British military leaders. The small single barrel gun was only 13 or 14 pounds in weight, not much more than a Martini-Henry. This could have been the predecessor of the Bren gun or a squad fielded mobile machine gun. The navy thought of the rifle caliber Nordenfelt as a gun to sweep the decks of an enemy ship prior to boarding, which with the big guns of the time was highly unlikely anymore. The army only thought of the machine gun as a defense for their artillery, or just an adjunct to the infantry in fending off human wave attacks. If the British military had been forward thinking, this could have advanced tactics by at least 40 years.