A mitrailleuse (French pronunciation: from French mitraille, "grapeshot") is a type of volley gun with multiple barrels of rifle calibre that can fire either multiple rounds at once, or several in rapid succession. 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 calibre) centre-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 six 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 mitrailleuses were in existence at the beginning of the Franco-Prussian War in 1870. Their field use was discontinued by the French Army after 1871. After the Gatling gun was replaced in service by newer recoil- or gas-operated weapons, the approach of using multiple barrels fell into disuse for many decades. However, some examples were developed during the interwar years, but only existed as prototypes, or were rarely used. The word mitrailleuse nonetheless became the generic term for a machine gun in the French language because of its early appearance in the field of weapons, although the mitrailleuse itself was manually operated.
In modern French, mitrailleuse is the word used for machine gun, including modern fully automatic weapons.
The first "mitrailleuse" was a manually fired 50-barrel volley gun originally developed in Belgium in 1851 by the Belgian Army Captain Fafschamps, who made a rough prototype and drawings of his invention. The system was improved during the 1850s by Louis Christophe and the Belgian engineer Joseph Montigny, with the completion of the 37-barrel Montigny mitrailleuse in 1863. From 1859, Joseph Montigny proposed his design to Napoleon III, which led to the development of the French Reffye mitrailleuse, designed by Jean-Baptiste Verchère de Reffye with the collaboration of Montigny, and which was adopted by the French Army in 1865. Initially kept under wraps as a secret weapon, it became widely used in battle by French artillery during the Franco-Prussian War (1870–71). Smaller numbers of other designs, including the Gatling gun, were also purchased by the French government during the latter part of that conflict. The Reffye model had initially been built in small numbers and in secrecy: only about 200 were available at the beginning of the conflict. This also kept regular French field artillery in a neglected position in the eyes of French emperor Napoleon III, with dire consequences during the Franco-Prussian War of 1870–71.