(Fig. 4)

The grenade is fired from the 3 cm rifled discharger cup which can be fitted to the 7.92 mm Mauser rifle and also to a modified version of the 7.92/13 mm A-tk. rifle (Pz.B. 39). The propellant cartridge contains a wooden bullet.

The rustproofed steel body of the grenade tapers slightly towards the head (1.8 to 1.5 inches) and is fitted with a parabolic impact cap, also of steel. At the base of the body a cylindrical tail unit is fitted. This is 2.9 inches in length and 1.2 inches in diameter with a pre-engraved 3 cm band near its base. The tail unit may be of aluminium alloy or may be of black or brown plastic with a steel connecting shank and contains a graze fuze and a gaine. The overall length of the grenade is 7.15 inches and the weight, 13 oz. 5 drs.

The body contains a 4 oz. 6 dr. charge of cast T.N.T. in which the "hollow" is in the form of conical cavity with a steel liner. The liner is coned at 19.5 degrees, has the apex cut away and the hole sealed by solder. At the top it is shaped to engage a supporting can-nelure in the body and is fitted with a steel disc which has a small central hole. The im-pact cap is supported on the disc and the assembly is secured by the spun top of the body. At the base the body is reduced in diameter to match the tail unit and contains a 2.75 dram exploder pellet of P.E.T.N./wax. The base is closed by two cardboard washers.

The plastic tail unit is connected to the body by a steel shank which is screwed to the body and secured to the plastic by the latter being extruded into perforations in the shank. Eight rifling grooves are formed in the band near the base of the unit. The interior is recessed from the top tp accommodate the small cylindrical gaine and from the base to receive the fuze with its steel screwed base plug. The diaphragm between the upper and lower recess is drilled to provide a passage for the needle and to receive a flash pel-let which is secured by a perforated screwed plug.

The fuze consists of an inertia pellet carrying a needle which is held away from the flash pellet by a coiled spring strip supported on a washer secured to the head of the pellet. The coil is held within an arming sleeve which is supported by a spiral spring held in com-pression between an external flange on the sleeve and a collar at the base of the inertia pellet. The sleeve is prevented from rising, under the pressure of the spring, by a retain-ing spring which is secured to the head of the pellet and has four arms which engage a circular groove inside the sleeve. A second internal groove is formed near the top of the sleeve to engage with the arms when the fuze is armed.

The 7.92 mm and 7.92/13 mm S.A. cases are of vanished steel and are fitted with short hollow bullets of wood. The 7.92 mm case is extended in length at the mouth and is co-ned into a cannelure in the bullet. The propellant charge consists of 19.6 grains of nitro-cellulose powder in the form of square flake with a ridge across the centre of one side of the flake. The flakes are 0.055 inch square, 0.01 inch thick and the ridge protrudes 0.01 inch. The ridge is probably intended to prevent the flakes packing tightly together. The composition of the propellant includes 98.36 per cent. of nitrocellulose (nitrogen content 13.12 per cent) and 0.88 per cent. of diphenylamine. The 7.92/13 mm propellant charge consists of 51 grains of nitrocellulose powder in the form of granular tubes. The dimen-sions of the tubes in inches are: length 0.050, external diameter 0.084 internal diameter 0.04.

On acceleration the arming sleeve sets back, compressing its spring, and is prevented from rebounding by the arms of the retaining spring entering the internal groove near its head. The coiled steel strip is then free to expand so that on graze the pellet passes through the coil and the needle pierces the flash pellet. The flash enters the detonator in the gaine which brings about the detonation of the bursting charge with the assistance of the exploder. The functioning of the fuze, as the result of the strike of the impact cap, brings about the detonation at the effective point relative to the surface struck and the hollow in the head of the charge results in the concentration of the effect of the de-tonation to obtain perforation. The steel disc under the cap is probably intended to pre-vent debris from the cap entering the liner.

Perforation of 50 mm homogeneous hard armour has been obtained at 30 degrees to the normal. The main dimensions of the hole were 5/8 x 3/8 inch.

Fig. 4