(Fig. 23)

The shell is fired from the 37 mm. 40 calibre Q.F. A.A./A.Tk. gun. The body of the shell is coloured pale blue, the nose red, and is stenciled as indicated in the diagram. The total length of the round is 13 inches, the brass cartridge case being 7.9 inches long. The to-tal weight of the complete round is 2 lb. 13 oz.

The shell is in two parts, a steel head drilled and tapped internally to take the fuze des-cribed below and threaded externally to fit into the comparatively thin walled body. The wide driving band is of copper. The weight of the filled and fu-zed shell is approximately 1 1/2 lb. The head is not hardned.

The bursting charge comprises 1 oz. 7 drs. of chopped strip ballistite. There is no explo-der system.

The cartridge case is of brass 7.9 inches long, is fitted with primer Mod. 930 described in Pamphlet No. 9. The propellant charge is 3 oz. 5 drs. of the normal Italian ballistite des-cribed elsewhere in this pamphlet.

Fig. 23

The graze action fuze, which bears no Italian designation, screws internally into the steel head of the shell. It consists of a hollow brass body in the forward end of which an igni-ferous detonator is secured by a detonator plug of the usual design.

The hollow brass inertia pellet carrying a flat steel needle is positioned within the body by means of the brass split ferrule and the base plug. The inertia pellet and base plug are filled by perforated gunpowder pellets.

It has been found that a force of 45 lb. is required to force the inertia pellet through the split ferrule; this would be reduced in flight by the centrifugal forces acting upon the fer-rule. It is not clear from available data whether this ferrule is designed to set back over the pellet during acceleration, thereby arming the fuze, or whether the pellet is designed to set forward through the ring upon impact.

Flash from the detonator upon impact is boosted through the perforated powder pellets, thereby firing the ballistite charge.

Fig. 24