The Japanese Model 99 (1939) 7.7-mm caliber light machine gun, a weapon of relatively recent
development, (see accompanying sketch) is very similar to the Model 96 (1936) 6.5-mm gun. Nearly
all variations result from the change to the larger caliber. The general characteristics as
reported by the Aberdeen Proving Grounds, follow:
Weight w/o magazine | | 20 lb |
Overall length | | 42 in |
Weight of barrel | | 6 lb |
Length of barrel | | 21 3/4 in |
Rifling | | 4 lands and grooves (left hand uniform twist) |
*Rate of fire | | 800 rpm (automatic fire only) |
*Muzzle velocity | | 2,300 fps |
Front sight | | Flat post |
Rear sight | | Drum type with click adjustment for windage and elevation. |
An adjustment for headspace is incorporated in the barrel retaining bolt. A
tapered groove is cut into the barrel near the breech and a corresponding
tapered surface is milled into one side of the locking bolt. As the locking bolt
is drawn from left to right by means of a large hexagonal nut which pivots on the
outer end of the bolt lock and screws on to a fixed collar, the barrel is forced to
the rear, thereby decreasing headspace. The bolt lock nut is marked from 1 to 8. On
the forward face of the receiver, to which the barrel is held in close contact, a
washer is provided so that the replacement can be made as excessive wear occurs. The
washer is about 1/16 inch in thickness.
An adjustable rear monopod is provided which is mounted in a recess in an
extension of the butt plate. A flash hider is screwed onto the barrel in the
conventional manner rather than attached by a bayonet-type lock as is found on the
Model 96. The staggered box-type magazine is longer and slightly less curved
than the one used for the Model 96. The safety lever on the Model 99 is located
on the left side while on the Model 96 it is on the right. Ammunition for
the Model 99 light machine gun is rimless.
*Not checked by Proving Ground Test.