Type 03 vs Type 92 Machine Gun

Type 03 and Type 92 machine gun (Japan)

Type 03 machine gun

Type 92 machine gun, spade grips folded
Image courtesy of James D. Julia auction house, Maine, USA

Type 92 machine gun, spade grips in combat position, tripod is mounted with carrying "stretcher" type handles
Image courtesy of James D. Julia auction house, Maine, USA

30-round rigid strip with 7.7mm Type 92 ammunition, as used in Type 92 machine guns

	Type 03 machine gun	Type 92 machine gun
Caliber	6.5x50SR	7.7x58SR Type 92
Weight	26.5 kg (gun body) + 24 kg (tripod)	28 kg (gun body) + 24 kg (tripod)
Length	1200 mm	1156 mm
Barrel length	737 mm	720 mm
Feed	Rigid strips, 30 rounds	Rigid strips, 30 rounds or semi-rigid belt 250 rounds
Rate of fire	450 rounds per minute	450 rounds per minute

The first domestically designed Japanese machine gun was the Type 03 Taisho which appeared in 1914. It was somewhat similar to the French Hotchkiss medium machine gun, although General Kijiro Nambu, the designer of the gun, made numerous changes to the feed, fire controls and locking system of the weapon. During the late 1920s and early 1930s the IJA decided to improve the lethality and effectiveness of its machine guns by adopting a more powerful cartridge to complement the mildly powerful 6.5x50SR ammunition then in general use. In 1932 the IJA adopted the 7.7x58SR Type 92 ammunition and the Type 92 medium machine gun to fire it. The ammunition was a semi-rimmed version of the British .303 round (7.7x56R), and the gun was a slight modification of the Type 03 machine gun. The new round obviously increased the capabilities of infantry machine guns, but it also made Army logistics more complicated. The Type 92 machine gun (known among WW2-era US soldiers in Pacific as "woodpecker" for its peculiar slow-rate firing sound) was the main medium machine gun of Japanese army through the WW2.

The Type 03 machine gun is a gas operated, air cooled, automatic-only machine gun. The barrel of the gun is finned in its front part (ahead of the gas port). Barrel replacement requires the use of a special wrench and cannot easily be done in combat. The rear part of the barrel is enclosed within a massive barrel jacket with large radial fins. This jacket is permanently attached to the receiver and carries provision for mounting the gun to the tripod or other mount.
The basic action employs a long-stroke gas piston, located below the barrel. The gas system is provided with a manual gas regulator. The gas piston operates the strip feed (through a cam cut in its operating rod) and the bolt group, through a projection with inclined surfaces on the rear of the operating rod. The bolt only has a linear motion, bolt locking is provided by a separate wedge-shaped lock which is connected to the rear of the bolt and permitted to slide up and down. This lock has two locking lugs (one on either side) which engage locking recesses in the receiver walls. To lock the bolt, the lock is lowered through the interaction with the inclined surfaces on the hook-shaped projection of the operating rod. To unlock the bolt after each discharge, it is lifted by a cam surface on the operating rod during the early rearward movement of the gas piston / operating rod. The locking wedge has a channel in the center for the firing pin, which is operated by the projection on the operating bolt once the bolt group is fully in battery and locked. The shape of this channel prevents forward movement of the firing pin unless the lock is fully seated in the receiver and thus the bolt is safely locked. Firing is from an open bolt, in automatic mode only.
Firing controls include dual spade grips with interlinked dual triggers. No manual safety is provided. The Type 92 machine gun featured an updated fire control group which includes folding horizontal grips with a single thumb-trigger in between, and the addition of a manual safety.
Feed is via Hotchkiss-type rigid metal strips, feed direction is from left to right only. Since the gun mechanism provides no primary extraction, an integral oiler is built into the feed unit. Each cartridge in the strip passes below a brush built into the top feed cover. When the cartridge is drawn across the feed, it pushes the oiler valve and small amount of oil is squirted into the brush and then transferred to the cartridge before it reaches the feeding position.
The standard mounting is a solid infantry-type tripod with traverse and elevation mechanisms. The tripod can be adapted for the AA role with the introduction of a special adapter rod. The tripod is unusual in that it has provision for the attachment of carrying poles at the two front legs and a special carrying fork at the rear leg. That way, the gun on its mount can be carried across the field by two or more soldiers, like a stretcher.