DESCRIPTION: It is used in shell for heavy guns, the ammunition of which is often of na-val design.

The fuze is of the combined direct action and graze type and, with the exception of the igniferous detonator, has no explosive filling. (See fig. 571.) The design includes a hole at the nose to receive an extended form of hammer for use under a ballistic cap.

The aluminum body of the fuze is screw-threaded externally at the base for insertion into the shell and recessed internally to take an aluminum striker holder and the graze mecha-nism.

The striker is of steel and is secured by a steel plug which screws into the striker holder. The striker holder is supported in the body by a brass shearing wire. The stem of the striker is surrounded by a creep spring and the point protrudes into the top of the inertia pellet.

An aluminum pellet holder with a central flash hole at the base and recessed internally to house the inertia pellet is screwed into the base of the fuze. On top of this holder are fixed five pivots on which are mounted five brass centrifugal segments surrounded by an expanding spring ring of phosphor bronze which maintains them in position overlapping the top of the interia pellet and preventing it from forward movement.

The inertia pellet which is of steel, brass plated, has a central cavity housing the ignifer-ous detonator and is closed at the base by a paper washer and a brass screwed plug with a central flash hole.

The detonator consists of a copper shell closed at each end by a copper disk 0.003 inch thick and contains 2.3 grains of composition above 0.86 grain of glazed gunpowder. The composition is made up of mercury fulminate 27.7 percent, potassium chlorate 38.7 per-cent, antimony sulphide 26.9 percent, and ground glass 6.7 percent.

ACTION: On acceleration the striker is prevented from setting bach onto the detonator by the shear wire. Centrifugal force set up by the projectile in flight causes the spring ring to expand and permit the segments to rotate clear of the inertia pellet thus leaving the striker and inertia pellet held apart by the shear wire and creep spring. On graze or impact the shear wire is broken and the spring is compressed by the striker being driven in the graze pellet setting forward. The flash produced by the striker piercing the deto-nator passes through the flash channel to the gaine of the shell.

Figure 571 – K.Z. C/27 (LM)