This is a smaller model of the C/22 electric primer described in Pamphelt No. 4, page 31, and is used in the cartridge for the 20 cm light spigot mortar and in the fixed Q.F. cart-ridge for the 3.7 cm Kw.K. (Tank gun). The primer corresponds to the percussion primer C/13 in dimensions and is identified by the designation "C/23" stamped in the base. The contact plug is visible in a chamfered hole in the base.

The brass body has two key flats formed at the base and is screwthreaded for insertion in the cartridge. The diameter over the threads is 0.52 inch and the threads 18 to the inch.

The brass contact plug, contained inside the lower part of the body, is cylindrical in shape with a stem at the bottom which emerges through a chamfered hole in the base of the body for contact with the firing mechanism. A small lug is formed near the top of the plug which fits into a recess in the body to prevent rotation. A layer of light brown insu-lating composition coats the side wall of the plug including the stem and the greater part of the top. The top of the plug is recessed to contain gunpowder and the electric fuze head which extends radially across the plug. The fuze head consists of an upper and a lower contact strip with insulating material between them and a bridge wire at one end surrounded by a blob of ignition composition. The lower strip is in contact with the top of the contact plug whilst the upper strip is in contact with a projection inside the brass contact washer assembled above, but insulated from, the plug. The washer, in addition to this projection, has two external projection or lugs which engage in recesses inside the body and prevent rotation. A screwed plug with a central flash hole and a concave underside is screwed into the body to secure the contact washer and cover a priming of gunpowder surrounding the fuze head. The magazine in the top of the primer contains a pellet of gunpowder and is closed by a thin metal disc. The weight of the pellet is ap-proximately 7 grains.

The path of the firing current is from the firing mechanism, through the con tact plug to the lower strip of the fuze head, through the bridge wire to the upper strip thus heating the wire and igniting the composition and thence by the contact washer, through its in-ner projecting piece, through the body to earth.

Fig. 12