The Madsen was a light machine gun that Julius A. Rasmussen and Theodor Schoubue designed and proposed for adoption by Captain Vilhelm Herman Oluf Madsen, the Danish Minister of War, and that the Danish Army adopted in 1902. It was the world's first true light machine gun produced in quantity. Consequently, Madsen was able to sell it in 12 different calibres to over 34 different countries worldwide, where it saw extensive combat for over 100 years. The Madsen was produced by Compagnie Madsen A/S (later operating as Dansk Rekyl Riffel Syndikat A/S and then Dansk Industri Syndikat A/S).
The design dates to 1880s with the Danish Forsøgsrekylgevær (Self Loading rifle M.1888) being a precursor design. In 1883 Captain Vilhelm Herman Oluf Madsen (a Danish artillery officer), and Rustmester Rasmussen (a weapons technician at the Danish Arsenal), began working on a recoil-operated self-loading rifle; Madsen developed the idea and Rasmussen fabricated the actual weapons. The rifle used a non-removable stripper clip that used gravity to feed rounds to the action; when the gun was not in use one could fold the clip down to cover the opening. The rifle used the 8×58RD cartridge, first in black-powder and then in a much more powerful smokeless powder version. The design was not successful. An improved design in 1896 gave the rifle an enclosed, but still gravity-fed, magazine. This version saw some 50–60 rifles being produced, but they were only issued to the Danish navy for use by coastal fortifications troops. Investors formed a company (the Dansk Riffel Syndikat; DRS), in 1898 to commercialise the rifle, and bought the patent rights from Madsen and Rasmussen in exchange for royalties on future production. By this time Madsen had left the project to become Minister of Defence in Denmark. In 1899 Lieutenant Jens Schouboe became the manager for the DRS, and a number of subsequent patents bear his name. Consequently, the Madsen rifle is sometimes referred to as the Schouboe rifle. In 1901 he patented the design for the Madsen machine gun. The original Madsen machine guns used black-powder cartridges that quickly jammed the action. However, once the design was tried with 6.5mm smokeless powder rounds it worked well. The Madsen has a rather sophisticated and unique operating cycle. The machine gun uses a mixed recoil-operated locking system with a hinged bolt that is patterned after the lever-action Peabody Martini breechblock. The recoil operation is part short and part long recoil. After firing a round, the initial recoil impulse drives the barrel, barrel extension, and bolt to the rear. A pin on the right side of the bolt moves backward in grooves in an operating cam plate mounted to the right side of the receiver. After 12.7 mm (0.5 in) of travel, the bolt is cammed upward, away from the breech (the "short" portion of the recoil system). The barrel and barrel extension continue to move rearward to a point slightly exceeding the combined overall length of the cartridge case and projectile (the long portion of the recoil system, responsible for the weapon's low rate of fire). After the breech is exposed, an odd lever-type extractor/ejector, mounted under the barrel, pivots to the rear, extracts the empty case, and ejects it through the bottom of the receiver. The bolt's operating cam then forces the bolt face to pivot downward, aligning a cartridge feed groove in the left side of the bolt with the chamber. While the bolt and barrel are returning forward, a cartridge-rammer lever, mounted on the barrel extension, pivots forward, loading a fresh cartridge.