(Fig. 22)

This primer has been encountered in the 76 mm. 40 cal. Q.F. round described elsewhere in this pamphlet.

The primer body is of brass flanged at the base and threaded externally for insertion in the cartridge case. The diameter across the screw threads is about 0.44 inches. The interior of the body carries a small recess at the base into witch the cap and anvil are secured by means of a brass fire-hole plug. The latter closed at the top by a paper disc.

The copper cap contains 0.3 grains initiatory composition composed of Mercury Fulminate 23 per cent., Potassium chlorate 41.5 per cent., Antimony Sulphide 35.5 per cent. The composition is protected by an unvarnished tin foil disc.

The magazine contains 9 grains of gunpowder and is closed by a varnished mill-board disc over tissue paper.

The base of the primer is struck centrally and crushes the initiatory composition against the anvil, flash passes through the fire hole plug and so initiates the magazine and pro-pellant chase. Sealing of propellant gases is effected by expansion of the primer walls into the primer boss and by the solid construction of the base.

Fig. 22