A.P. types of cartridges have a red base marking. Ball and practice types of cartridges have a green base marking. Cartridges containing an incendiary charging have a black base marking. In the case of the armour-piercing incendiary cartridge, the red to indicate A.P., or black to indicate incendiary is used.

Cartridges containing high-velocity propellant charges have a green tip to the bullet. Where a tracer is included and in consequence the tip is black, a green ring is marked below the black tip*. The high velocity armour-piercing cartridge with tungsten carbide core is an exception to this system of green marking.

A description of the types of cartridges cases and initiator caps used with this ammuni-tion is given in Pamphlet No. 2. The general appearance and base stampings of a typical cartridge are shown in Fig. 1, which also gives the significance of the stampings where known. Wads between the propellant and bullet are not used.

The brass caps are secured by three stabs and contain an approximately 0.44 grain filling consisting of mercury fulminate, potassium chlorate, antimony sulphide and glass. The composition is varnished on the surface and covered with a disc of metal foil, the edge of the disc being upturned round the wall of the cap. The anvil formed in the cap cham-ber of the case is indented into the foil disc.

The propellants vary in nature and form with the various types of cartridges, but in all types it is in granular form either as flakes or tubes.

The flake propellant is graphited and is a nitrocellulose powder consisting basically of 94.97 per cent nitrocellulose (Nitrogen content 13.22 per cent), with diphenylamine as a stabilizer and ethyl carbamite. Potassium sulphate is also included, presumably to reduce the flash. The dimensions of the flake are 0.06 x 0.05 x 0.04 inch. This propellant is nor-mally used in types other than the high-velocity cartridges, the charge weight varying between 44 and 45 grains.

Two nature of graphited tubular propellant are used. One is used in the high-velocity cartridges in which the bullets bear green marking, the other is used in the high-velocity A.P. cartridge with tungsten carbide core.

The propellant used in the cartridges bearing the green marking consists basically of ap-proximately 60 per cent of penta-erythritol-tetra-nitrate with 32 per cent of nitrocellu-lose (Nitrogen content 12.5 per cent). The stabilizer is diphenylamine and ethyl centralite is used as a moderant. Potassium sulphate is also included, pressumably to reduce the flash. The average dimensions of the tubular grains are:– length 0.07 in., external diame-ter 0.049 in., internal diameter 0.011 in. The charge weight varies between approxima-tely 52 and 53 grains and the velocity is increased by approximately 300 f.s.

The propellant used in the high-velocity A.P. cartridge with tungsten carbide core con-sists basically of approximately 34 per cent of penta-erythritol-tetra-nitrate with 56 per cent of nitrocellulose (Nitrogen content 13.2 per cent). The stabilizer is diphenylamine. Ethyl centralite and dinitrotoluene are included presumably to moderate the rate of burn-ing. The average dimensions of the tubular grains are:– length 0.063 in., external diame-ter 0.047 in., internal diameter 0.008 in. The charge weight is approximately 55 grains and the velocity is increased by approximately 200 f.s.

Total weights given above are for steel cartridge cases. Weights for brass cartridge cases are 7 - 9 grains lighter.