(Fig. 37)

1. These charges are designed on the "hollow charge" principle and are intended for the perforation of armour plate.

2. Two types are known to exist; the 12.5 kg (27.5-lb.) charge and the 50 kg (110-lb.) charge.

3. The 12.5 kg charge consists of a light metal bell-shaped container which contains the T.N.T. blasting charge with a hemispherical cavity and an intermediary prepared to recei-ve a detonator. The charge container is fitted with a handle for transport.

4. The 50 kg charge is made up in two parts for convenience in handling, each part being provided with a handle, and one part is superimposed on the other when positioned for use. The containers are both of light metal and are shaped to fit closely together when assembled. The T.N.T. filling of the inner part has a hemispherical cavity while the filling of the outer part, also T.N.T., includes an intermediary prepared to receive a detonator.

5. The charges are positioned with the flat surface on the plate and are initiated by means of a detonator of the normal type which is inserted in the intermediary and ignited by means of a length of safety fuze and a friction igniter.

6. The perforation performance of these charges is reported to be as follows:–

A 50 kg charge followed by a 12.5 kg charge, laid on the same spot, will perforate up to 11.8 inch armour plate.

Two 50 kp charges fired in succession over the same spot, will perforate up to 19.7 inch armour plate.

The charge has to be positioned to provide a good contact between its hollowed side and the plate. The hole produced is usually about 3.9 inches in diameter on the exterior surface of the plate and 23 inches on the interior surface.