Japanese Mobile Firepower of the Pacific War: The Nambu Type 99 Light Machine Gun

By Edwin Libby

In the battle for Attu Island of the Aleutians chain off Alaska, soldiers of the American 7th Infantry Division encountered in May of 1943 a new type of light machine gun being used by the Japanese defenders of this piece of United States property, captured in June of 1942. The attacking U.S. troops discovered that this new weapon, the Nambu type 99 ( 7.7 mm) light machine gun, had been issued, almost exclusive of other Japanese LMGs, to all units of the 2300-man Japanese garrison which held the island. After Attu, American forces encountered the Type 99 Nambu LMG in every major land battle fought with the Japanese.

The Type 99 Nambu light machine gun originated with a design advanced by Lieutenant General Kkjiro Nambu in an Imperial Army competition for a new and more powerful weapon of this kind, and his design was adopted as the new Army standard LMG in 1939. The 7.7mm Type 99 LMG was viewed as an improvement over the 6.5mm Type 96 LMG, the preceding service standard that also had been designed by Nambu. Controversy over the development and adoption of the Type 96 predecessor centered on its 6.5mm cartridge that was thought by some to be inadequately powerful to meet the destructive capabilities expected of a weapon of this type. Although the 6.5mm cartridge produced sufficient range and excellent accuracy in the small arms in which it was used, it readily was apparent in comparison with the 7.7mm rimless machine gun cartridge recently adopted. It was also lacking in bullet diameter, size, and weight, and in muzzle energy required for the development of armor-piercing, tracer, incendiary, and other special purpose ammunition in common use with light machine guns. As well, by the late 1930’s the Japanese were very much aware of the superior capabilities of light machine guns of heavier calibers used by the major world powers, most of which had found their way into the motley armamentarium of their Chinese enemies and onto the battlefields upon which the Japanese fought. Official Japanese adoption of the Type 99 Nambu light machine gun in 1939 settled the LMG controversy and it placed Japan on par with the major world powers in possessing a first-rate weapon of this kind.

Designated Kyukyu Shiki Keikikanju, or “99 Type Light Machine Gun,” this weapon commonly was called Kyukyu Shiki Keiki, or “Type 99 Light,” by Japanese troops in the field. The Type 99 Nambu LMG essentially was a slightly redesigned Type 96 Nambu LMG strengthened substantially in its construction to handle a heavier cartridge. The Type 99 bore a close resemblance to the Type 96. The Type 99 Nambu LMG was a gas-operated, air-cooled, full-automatic, magazine-fed 7.7mm shoulder weapon with bipod which, like its 6.5mm Type 96 counterpart which was still being used in the field, was fired basically from the prone position. To steady the weapon in this position, a folding, adjustable monopod was fixed to the heel of the buttstock, a feature lacking in the Type 96. A 30-round box magazine with staggered feed was mounted on top of the gun’s receiver and the magazine was held in place by a magazine catch with a large oval-shaped release lever which provided a convenient quick release in changing magazines. Sights on the Type 99 Nambu were of iron with an inverted V blade protected by guards at the front and a drum-controlled peep with a windage adjustment at the rear. A 2.5 power optical sight that could be mounted on the top rear of the receiver was provided as an accessory, but this sight could be used only under favorable conditions of good light and clear visibility, and hence often it was not used. A rigid carrying handle, like that of the Type 96 LMG, was fixed to the top of the barrel just ahead of the receiver, and it offered a convenient one-handed grip for the gunner who had to move his position in a hurry. A nut-and-wedge barrel locking device was employed on the Type 99, and this device was a distinct improvement over the rotating locking lever of the Type 96 LMG, especially with regards to strength of the barrel to receiver connection. The nut-and-wedge lock of the Type 99 LMG was used with barrel headspace washers of varying thickness to allow headspace adjustment to control and eliminate gun malfunctions caused by cartridge case separation, a problem often encountered with the Type 96 LMG as a condition of wear. The Type 99 Nambu LMG weighed about 21 1/2 pounds with magazine and sling, and it was slightly but noticeably heavier than the Type 96. No doubt the Japanese Army officers who approved the Type 99 LMG as the successor to the Type 96 thought the Type 99’s heavier 7.7mm caliber and the special types of ammunition it could use justified the increase in the gun’s weight over that of the Type 96. However, the Type 96 LMG remained the favorite of the Japanese gunners in the field. When their units were in retreat, and especially under the conditions of the jungle warfare of the Southwest Pacific area, they often retained their Type 96 LMGs while leaving their Type 99 LMGs behind. Although this fact led to speculation among our forces that the Japanese favored a lighter weapon and demonstrated a disdain for the Type 99 LMG by leaving them behind, more likely a shortage of 7.7mm ammunition caused the Type 99’s abandonment.

After 1943 the Type 99 LMG was the only one of Kijiro Nambu’s LMG designs left in production and it truly became the standard Japanese infantry LMG. In the course of its production history more than 46,000 Type Nambu LMGs were produced in three government arsenals and in two government-supervised private manufacturing companies. Despite heavy bombing of Japanese arms-producing factories and facilities, the Japanese continued to turn out Type 99 LMGs for frontline use and, although the quality of manufacture and materials used deteriorated as the Pacific War progressed, the Type 99 LMGs produced remained reliable, efficient, and formidable. The Type 99 Nambu LMG was rated by U.S. Ordnance personnel and by those who faced it in combat as one of the best LMGs of its time.