九七式自動砲: The Japanese Type 97 20mm Anti-tank Rifle
by Christopher Bailey
In the middle part of the 1930′s, it became apparent to nearly all observers that another war was on the horizon. Recalling the lessons of the First World War, nations around the world each began their own program to design and perfect a man-portable anti-tank weapon. The most obvious solution at the time, and the one that most designers chose as their starting point, was the World War One German concept of an “anti-tank rifle”. The first such gun, the Mauser 1918 Mauser T-Gewehr, was itself simply a scaled up Model 98 rifle. Chambered for a newly developed 13mm round, the T-Gewehr was a capable and effective battlefield rifle, and further development of this line of weapons was a reasonable solution at the time.
From this prewar “arms race” came a number of competing designs, amongst them the Polish Wz-35, the German PzB 38, the British Boys Rifle as well as the Solothurn series of commercial guns. These rifles, all using different mechanisms, show off a variety of design compromises. Some used a small high-velocity bullet fired out of a light weight gun, while others used a large projectile fired out of an equally heavy weapon. The middle ground (that of a medium sized round) was also employed, though it was largely overlooked by most designers Not to be left behind by these European developments, the Empire of Japan began its own program in 1935, culminating in 1937 with the adoption of the Type 97 Anti-tank rifle.
Chambered for the powerful 20x124mm cartridge, the Type 97 is a magazine fed, gas-operated weapon that fires from an open bolt. More like a small artillery piece than a traditional self-loading rifle, the whole receiver and barrel assembly of the Type 97 actually slides front-to-back during firing. While designed only for semiautomatic fire, there are reports of guns firing fully automatic. These seem to be either mechanical malfunctions or simply accounts of the Type 98, a fully automatic machine cannon derived from the Type 97.
When fully assembled with its armor shield and carrying handles, the gun weighed in at an astonishing 150 pounds. Unlike other heavy designs that came equipped with wheeled mounts or skis, the Type 97 was carried by its crew much like an injured man on a stretcher. This heft, coupled with the guns accessories and ammunition would have certainly place a large burden on the nine man crew during cross country operations. The barrel, which could be removed for long distance transport, was locked to the receiver using an interrupted thread mechanism.
Once the gun had been carried to its destination, the crew would adjust the three legs and lower the weapon into its firing position. To cock the weapon, the charging handle located on the left side would have to be pulled fully to the rear, with a loud “click” letting the shooter know that the sear had engaged the bolt carrier. After ensuring that both dust covers were open, a loaded magazine would then be locked into place on the top of the gun. At this point, the gun was ready to fire.
After loading the weapon, the gunner would lay the gun on his target. This was accomplished using a rear peep sight and a blade front sight. Traversing the gun was actually somewhat difficult, requiring the gunner to lift the rear of the heavy gun with his shoulder before shifting it left or right. Elevation could be adjusted in the similar manner, or by raising and lowering the rear monopod leg via its knurled grip. An assistant gunner would grip both forward legs to steady the gun during the firing, a position that must have been unnerving to those so assigned.
Once the gun had been appropriately sighted, the trigger would be pulled firmly to the rear, releasing the bolt carrier assembly. Driven forward by spring pressure, the bolt would strip a round from the magazine, feeding it into the chamber. The bolt carrier, continuing forward, would lock the action by forcing a locking piece into cutouts located in the sides of the receiver. Once fully locked, the firing pin would be struck be the carrier assembly, firing the cartridge.
As the projectile traveled down the barrel at 2,640 feet per second, some of the propellant gas was diverted into a regulated gas tube assembly located underneath the barrel. The gas acted directly against two integral gas pistons on the bolt carrier, forcing the bolt assembly to the rear and unlocking the gun’s action. The fired case was then extracted by the bolt and thrown out the bottom of the gun by an ejector mounted in the top of the receiver housing. Once fully to the rear, the sear would again catch on the bolt carrier, locking the action open until the trigger was pulled once more. Simultaneous to this internal action, the whole barreled action would cycle both forward and to the rear, its movement being slowed by the recuperator system mounted in the lower receiver. This additional complexity served to somewhat soften the recoil experienced by the shooter.
Production of the gun began in 1938 at the Kokura Arsenal, a facility best known for its small arms production throughout the Second World War. First seeing combat against the Red Army at the Battles of Khalkhin Gol in 1939, the Type 97 proved to be a disappointment to the Japanese military, with its 20mm round performing poorly against Soviet BT series tanks. This is somewhat surprising given the fact that wartime American testing demonstrated that the projectile could pierce about 30mm of armor at 250 meters range.
When one also considers the complexity of the gun and the difficulty of manufacture, it isn’t surprising that production of the gun was terminated in 1941 after some 1100 had been completed. As the war turned against Japan in 1943, the Nihon Seikosho Company (Japanese Steel Works) tooled up and produced another 100 guns, after which no more were made. Despite its limitations, the Type 97 continued to be a front line weapon throughout the war in the Pacific, usually being employed in a prepared static defense position. Very few examples of the gun survive today in either private hands or museums, almost certainly due to its bulk and great weight.
Caliber: 20 x 124mm
Mechanism: Gas-operated open-bolt semiautomatic
Length, firing position: 82.5 in (2096 mm)
Length, traveling position: 99.5 in (2527 mm)
Weight, complete: 150 lb (68.1 kg)
Weight, less shield and handles: 115 lb (52.2 kg)
Barrel length: 41.875 in (1064 mm)
Rifling: 8 groove
Magazine capacity: Seven rounds
Muzzle velocity: 2,640 feet per second (866 m/s)
Total production: Approximately 1200