(Figs. 18 and 19)

The 20 cm H.E. bomb, Model 40, is fired from the 20 cm Leichter Ladungswerfer (a spigot mortar with a 9 cm spigot) with a separately loaded cartridge.

The streamlined bomb has an ogival head with a Wgr.Z. 36 fuze, or a plug with a lifting loop, at the nose and has a tail tube carrying six vanes. The exterior is painted the nor-mal deep olive green and stencilled in black. The stencilling includes the H.E. numeral "13" near the nose (indicating amatol) and the weight class on the cylindrical part of the body. A fuzed bomb bearing the weight class marking "N" weighed 48.75 lb. The overall length, inlcuding the fuze, was 31.15 inches and the maximum diameter, approximately 20 cm. The bomb is supplied plugged and fitted with a cylindrical cover of cardboard and steel for the projection of the tail vanes.

The cartridge is short and cylindrical, the lower part being of steel with a partially flan-ged adapter for the C/23 electric primer at the base and a bakelite upper part. The ap-proximate dimensions are: length 2.2 inches, diameter 3.5 inches. A label giving details of the igniter and propellant charges is affixed to the top of the cartridge.

The bomb body is of pearlitic malleable cast iron with a screwthreaded fuze hole at the nose and a tubular extension formed at the base for the attachment of the tail unit. A large hole in the base of the body, within the tubular extension, is closed by a steel screwed pin. A steel fuze hole adapter, inserted at the nose, carries an exploder contai-ner of mild steel.

The tail unit consists of a short outer tube and an inner tube which carries the vanes. The outer tube is of chronium-silicon steel with a V.D. hardness figure of 262 and is clo-sed at the front end where the thickness is increased to correspond to a recess in the base plug. A small central hole in the closed end is formed probably for the escape of air during assembly. The inner tube is of mild steel and is also closed at the front end. The two tubes are retained in the tubular extension of the body by two grub screws inserted at diametrically opposite positions in the extensions. The rear part of the inner tube pro-trudes from the inner tube and has six vanes welded to it in pairs.

The weight of the empty bomb is 30.97 lb., the body alone weighing 16.65 lb.

The bursting charge consists 15 lb. 12 1/2-oz. of cast amatol 65/35 with a thin surround of T.N.T. to the exploder cavity. The exploder container carries the larger size of the C/98 P.E.T.N. gaine.

Fig. 18

The cartridge is in the form of a short cylindrical box consisting of a steel cup-shaped body with a cover of moulded plastic. The propellant charge, in three sections, is contai-ned inside with a steel igniter containing gunpowder.

The steel body has a hole in the base for the assembly of an adpater which carries the primer and around its exterior has a groove which is connected to the interior by a ring of radial holes and is covered by a steel obturating cup fitted over the base. The cup is expanded by the pressure of propellant gases through the holes. Inside the body there are three equally spaced steel studs protruding from the base for the support of the lowest section of the propellant charge. The obturating cup is supported at the base by a steel disc and the adapter. The steel adapter has an interrupted flange to enable the cartrdige to be inserted in the top of the spigot and to be locked to the spigot by turn-ing. A screwthreaded primer hole is formed in its base and at the front end it is screw-threaded externally to receive the steel igniter which secures it to the body.

The steel body of the igniter is in the form of a perforted cylinder which is closed at the top where it is shaped to form two flat surfaces for the tool used in screwing it to the front end of the adapter.

The plastic cover is an inverted cup with a cylindrical centre piece formed inside which is shaped to fit over and surround the igniter and has corresponding perforations. The cen-tre piece is screwthreaded near the top to receive a screwed plastic spider which sup-ports one of the charge sections. A second spider without a screwthread is used as a distance piece between the top of the charge section and the cover. The top of the cover is recessed and carries a white paper label giving the particulars of the propellant.

Both body and cover are stepped so that the cover fits into the body and the junction is sealed with a wrapping of adhesive tape.

The igniter contains a 55 grain paper wrapped, annular pellet of gunpowder inside of which there is a 20 grain filling of small grain gunpowder.

The 36 grain propellant charge of "Ngl.Rg.P. - 12.5 - (0,4 x 72/36)" a double base nitro-glycerine propellant in ring form, is divided into three sections of equal weight. Each sec-tion in the cartridge examined weighed 186 grains and consisted of a number of annular disc perforated with two rings of holes and roughened by an impressed pattern on both sides. The disc are secured by silk ties threaded through the perforations in three places. Each of the discs is between 0.014 and 0.018 inch thick and has a diameter of 2.8 in-ches. The diameter of the central hole is 1.4 inches. One section of the charge, with another placed on top of it, is supported on the three studs inside the steel body. The third section is carried inside the plastic cover where it is separated from the cover by a spider of plastic and supported by a similar spider screwed to the centre piece.

Fig. 19