The Japanese 8 mm submachine Gun, Type 100, is an automatic, air-cooled, magazine-fed, straight blowback-operated type, firing from an open bolt. Its basic design strongly resembles that of the German submachine guns. The weapon may be broken down into three main groups: a receiver which contains the bolt and driving spring, a barrel assembly, and a wooden stock assembly containing the trigger and trigger guard. A considerable amount of rough welding is used on the weapon; the front sight, bayonet lug, barrel lock, magazine well, driving spring guide, and trigger guard have all been attached to the rifle by this method. An unusual feature of the gun is a replaceable firing pin which screws into the face of the bolt.
The weapon has a high cyclic rate of fire, estimated between 800 and 1,000 rounds per minute.
It differs from the Type 100 (1940) Paratrooper’s rifle, described on page 204.1, in the following respects: it does not have a folding stock; a standard bayonet can be mounted directly on barrel and barrel jacket; and the rear sight is fixed rather than of the sliding ramp type.
SPECIFICATIONS
| Caliber | 8 mm (.315 in.) | |
| Weight with sling and magazine | 9 lbs., 2 oz. | |
| Weight of magazine | 9 oz. | |
| Length (overall) | 36 ins. | |
| Sight radius | ||
| Principle of operation | Straight blowback | |
| Feeding device | Curved box magazine | |
| Capacity of feeding device | 30 rounds | |
| Cooling system | Air | |
| Ammunition types | 8 mm pistol | |
| Rate of fire (cyclic) | 800-1,000 rds. per min. (est.) | |
| Type of sight—Front: | Inverted “V” | |
| Rear: | “V” with small peep additional. | |
| Weight of barrel | ||
| Length of barrel | 9 3/16 ins. | |
| Length of rifling | 8.3 ins. | |
| Rifling: | ||
| Twist | R.H . | |
| Form | ||
| No. of grooves | 6 | |
| Muzzle velocity | 1,050 f/s | |
| Maximum range | ||
| Effective range |
Japanese: p. 204.2 (August 1, 1945)