The demolition charge is approximately hemispherical in shape with three hinged teles-copic legs fitted to the hollowed base and a cylindrical projection, closed by a perforated coned cap, at the top. A fabric lifting handles is attached to the side. The exterior is painted the normal deep olive green. The complete charge weighs 30.5 lb., and has a diameter at the base of 13.5 inches.

The charge container consists of the cavity liner, the base ring (carrying the telescopic legs), the cover and the cap.

The cavity liner is hemispherical with an internal radius of 4.92 inches and consists of 4 superimposed close-fitting domes. The domes are spun to shape from 0.04 inch sheet steel and are drilled at the vertex for attachment by a deposit of weld metal. They are also attached by spot welding at two points, diametrically opposite near the base. This 4-ply construction of the liner has advantages over one of single sheet construction both of production and for the perforation performance of the charge. Failure of the do-mes to fit closely together may, however, affect the direction of the pressure and result in a perforation of an irregular shape.

The base ring is of 0.02 inch sheet steel and is soldered to the base of the cavity liner in the form of a flange. Three telescopic legs of strip steel are attached to the underside of the ring at equally spaced positions. The lengths of these legs are adjusted to position the charge, relative to the surface to be perforated, so that the maximum effect is ob-tained. The legs can be extended to 13.2 inches from the base ring.

The cover is almost hemispherical in shape and has a hole with a short cylindrical rim at the top. The sheet steel from which it is spun is 0.02 inch thick.

The cap is spun from 0.02 inch sheet aluminium and fits over the rim on the top of the cover. A central perforation is formed in the top of the cap for the insertion of a detona-tor.

The main filling consists of 21 lb. 3 oz. of cyclonite/T.N.T., 50/50 filled to a density of 1.66 by the "biscuit" filling process (i.e. cast, including broken slab). A cavity formed in the top of the main filling containe a perforated 27 dr. primer pellet of cyclonite/wax 95/5. The density of the pellet is 1.63.

With the legs fully extended and the charge fired at the normal to a 9 inch face-harde-ned plate the main dimensions of the perforation obtained were as follows:–