Tag Archive for '8mm'

8 mm Submachine Gun, Type 100 (1940)

8 mm Submachine Gun, Type 100 (1940)

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.


Caliber      8 mm (.315 in.)
Weight with sling and magazine9 lbs., 2 oz.
Weight of magazine9 oz.
Length (overall)36 ins.
Sight radius
Principle of operationStraight blowback
Feeding deviceCurved box magazine
Capacity of feeding device30 rounds
Cooling systemAir
Ammunition types8 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 barrel9 3/16 ins.
Length of rifling8.3 ins.
   TwistR.H .
   No. of grooves6
Muzzle velocity1,050 f/s
Maximum range
Effective range

Japanese: p. 204.2 (August 1, 1945)

8 mm Paratrooper’s Submachine Gun, Type 100 (1940)


This Japanese paratrooper’s submachine gun is a light, blowback operated, automatic weapon which fires the regular issue bottle-necked 8 mm pistol cartridge.

The gun, which is provided with a bayonet, also has a folding stock; that is, the stock is cut through just behind the receiver and hinged so that by releasing two locking hooks on the left side, the stock swings to the right and forward 180 degrees at the hinge and parallel with the barrel. The barrel and barrel jacket are held in place by a single screwpin threaded at the base and with a folding wingnut head, enabling changes without tools. The receiver assembly is machined in two units, with the units shrunk fit in final assembly.

Two features of the firing mechanism which are of unusual interest are the fixed firing pin which screws into the face of the bolt, and the feeding and chambering bar which insures that the cartridge is very nearly chambered before the firing pin can touch the primer.

In the illustrations above, the top picture shows the weapon as fired, and the photograph at lower left shows the method of folding. A bipod is frequently used with this gun as illustrated in the photograph at lower right.


Caliber       8 mm
Weight (without bayonet, magazine, & sightleaf) 7 lbs., 11 ozs.
Length (stock extended, without bayonet) 34 ins.
Length (stock extended, with bayonet) 49 ins.
Length (stock folded, without bayonet) 22.25 ins.
Sight radius 20 ins.
Principle of operation Blowback, bolt action
Feeding device Curved box magazine; staggered feed type.
Capacity of feeding device 30 rounds
Cooling system Air
Ammunition types 8 mm bottle-necked pistol cartridges
Rate of fire 400-450 r.p.m.
Type of sight Leaf
Length of barrel 9 ins.
Length of rifling 8.125 ins.
     Twist Uniform R.H., approx. 1 in 12
     No. of grooves 6
Muzzle velocity 1,080 f/s

Japanese: p. 204.1 (August 1, 1945)