Mitrailleuse (literally "grapeshot shooter") is the French word used to describe all rapid-firing weapons of rifle caliber.
Therefore the word "mitrailleuse", when used in the French language, applies to all machine guns including modern full automatic weapons. However in the English language the word "mitrailleuse" applies to volley guns with multiple barrels of rifle caliber. The earliest true "mitrailleuse" was invented in 1851 by Belgian Army Captain Fafschamps, 10 years before the advent of the Gatling gun. It was followed by the Belgian Montigny mitrailleuse in 1863. Then the French 25 barrel "Canon à Balles", better known as the Reffye mitrailleuse, was adopted in great secrecy in 1866. It became the first rapid-firing weapon deployed as standard equipment by any army in a major conflict. This happened during the Franco-Prussian War of 1870-71. A steel block containing twenty-five 13 mm (.51 caliber) center-fire cartridges was locked against the breech before firing. With the rotation of a crank, the 25 rounds were discharged in rapid succession. The sustainable firing rate of the Reffye mitrailleuse was 100 rounds per minute. The effective reach of the Reffye mitrailleuse extended to about 2000 yards, a distance placing their batteries beyond the reach of Dreyse needle rifle fire. Reffye mitrailleuses were deployed in 6 gun batteries and were manned by artillery personnel. They were not infantry support weapons but rather a form of special artillery.
Although innovative and capable of good ballistic performance, the Reffye mitrailleuse failed as a tactical weapon because its basic concept and operational usage were flawed. Furthermore only 210 Reffye mitrailleus were in existence at the beginning of the Franco-Prussian War in 1870. Their field use was discontinued by the French Army after 1871. In contrast, the Gatling gun became widely successful and even survives in powered form to this day. The word mitrailleuse nonetheless became the generic term for a machine gun in the French language, although the mitrailleuse itself was manually-operated. In summary, the excessive personal attention given by emperor Napoleon III to the mitrailleuse had distracted him from taking care of needed improvements to regular French field artillery . The side effect of his fixation on the mitrailleuse had dire consequences during the Franco-Prussian War of 1870-71.