Except for aerial bombs recently recovered, the only known use by the
Japanese of the hollow-charge principle is in the rifle grenade, (see
accompanying sketch) which is a copy of the German heavy AT rifle
grenade, Gr. G.Pz Gr (see
Tactical and Technical Trends No. 36, p. 34). The
launcher is clamped to the standard Model 38 (1905) 6.5-mm rifle. The
cartridge used to propel the grenade has a wooden bullet.
The sketch shows a sectionalized model of the grenade and illustrates the
Japanese use of the hollow-charge principle. The complete round is 7.98 inches
long and has a diameter of 1.58 inches at its greatest diameter. It has a bursting
charge of 3.81 ounces of TNT. The cone formed in the TNT is 2.5 inches deep
and 1.5 inches wide at the top.
The grenade is fired by impact with the target, a base-detonating inertia-actuated
fuze being carried in the rear of the projectile behind the bursting
charge. Since the fuze is not armed until the grenade has been fired from the
rifle and is in flight, the grenade is safe, to handle, but it should not be
jolted, since it is easily armed.
With the exception noted above, this is the only instance of the use by the
Japanese of the hollow-charge principle that has been discovered to date. It is to
be expected that they will employ it in other weapons. The penetrating effect
obtained is not dependent on impact velocity and the Japanese have in quantity a
variety of low-velocity weapons of fairly large bore suitable for firing
hollow-charge projectiles. Such weapons are the Model 92 (1932) 70-mm battalion
howitzer and the Model 41 (1908) 75-mm infantry (mountain) gun.