The Type 99 served the Imperial Japanese Army during most of World War 2. It was designed to take advantage of the newer and more powerful 7.7x58mm Arisaka rifle cartridge and replace the Type 96 Light Machine Gun of similar scope. However, production of the latter unit was such that both weapon types were fielded side-by-side for the duration of the war. The Type 99 proved an improvement over the previous form and lent itself quite well in the squad support role for which it was intended.
Origins of the Type 99 stemmed from the previous Type 96 Light Machine Gun, which itself was developed to replace the Type 11 series. The Type 11 and Type 96 both utilized the 6.5x50mm Arisaka cartridge which was the same ammunition used in the standard issue Type 38 infantry rifle series. The use of universal ammunition lent itself well for operations in the field where a soldiers of any class could supply one another with ammunition if need be. The modernized Type 96 was brought online in 1936 and proved successful once in the field. However, by this time, the IJA was interested in a more powerful rifle utilizing the more powerful 7.7x58mm Arisaka cartridge and developed the more modern Type 99 infantry rifle as a result. This now made the Type 96 a moot product and forced the development of a new light machine gun to support the new cartridge round.
The Type 99 was designed under the guidance of Kijiro Nambu (September 22, 1869 - May 1, 1949) and followed much of what made the Type 96 a field success for the IJA. Nambu made his career out of the Japanese military. Beginning in 1897, Nambu served under fabled Japanese weapon's designer Nariakira Arisaka and worked for several product developments. Nambu's tenure with the IJA formally ran from 1889 to 1924, achieving the rank of Lieutenant General in the process. Following his military career, Nambu founded the Nambu Arms Manufacturing Company to continue his ties with the Japanese military. Design of a light machine gun - the Type 99 - was begun in 1939 to which a military procurement contract followed for production to begin that year. The Type 99 entered service in 1939, alongside the still issued Type 11 and Type 96 series machine guns - and would serve the Imperial Japanese Army through August of 1945 - the Empire of Japan's final participation in the war.
The Type 99 fired the 7.7x58mm Arisaka cartridge from a gas-operated action. The weapon was fed from a top-loaded, curved 30-round detachable box magazine. Rate of fire was listed at 450 to 500 rounds per minute with a muzzle velocity of approximately 2,300 feet per second. The Type 99 weighed in at 11.4 kilograms and featured a running length of 1,181mm. The barrel measured in at 550mm. The barrel could be changed by the operator to prevent overheating and subsequent malfunction.
Externally, the Type 99 was decidedly Japanese in appearance, comparable to other weapons systems in this class, and characterized by the use of a finned gun barrel, curved magazine and flash suppressor as well as use of novel concepts such as a monopod at the stock and fittings for a bayonet. The receiver was blocky with much detail and contained the major internal working components of the weapon including the feed and cocking handle. The weapon was actuated via a straight pistol grip with applicable trigger group nearby. A rather short-length shoulder stock emanated from the rear of the pistol grip and lower portion of the receiver and sported some ergonomic features including a curved shoulder plate. The curved magazine was fed through the top of the receiver, ahead of the pistol grip unit with a magazine release lever identifiable to the rear of the magazine feed. A carrying handle was usually affixed to the forward portion of the receiver to facilitate in the transporting of the weapon. A gas cylinder ran underneath the barrel ahead of the lower forward receiver. The barrel continued a distance ahead of the cylinder and was capped by a conical muzzle flash hider. Interestingly, an infantry-style bayonet could be fixed to the underside of the gas cylinder for close-combat though this proved a rather useless feature at best. A folding bipod was also mounted to the barrel/cylinder bracket and used for stabilized supporting fire. A monopod was fitted to early production forms of the Type 99 LMG. Sighting was accomplished through a front blade and rear leaf sight. A telescopic sight was optional and, if fitted, was mounted to the right side of the receiver.
Beyond the base squad-level Type 99 model, a compact version was designed for use by Japanese paratroopers that fielded a detachable butt and barrel system. The design also featured a folding pistol grip and bipod. During the jump, the Japanese soldier would contain the entire weapon system in a handy carrying bag and assemble his weapon once landed on the ground.
Beyond the IJA, the Type 99 inevitably found itself in the inventories of China, North Korea and Taiwan.