EMPLOYMENT: This base fuze is of the graze type and used in German 3.7-cm A.P. Shell of Polish origin. (See fig. 604.)

DESCRIPTION: The fuze consists principally of a steel body, steel inertia pellet contain-ing detonating composition, brass ferrule, two steel balls, brass arming sleeve, a small and a large stirrup spring, and a felt disk.

The body is in two parts. The rear part is flanged, and screw-threaded externally for in-sertion in the shell. Internally, it is screw-threaded to receive the front portion, and bo-red in two diameters to accommodate the fuze mechanism. The front part is screw-threaded externally at one end for attachment to the rear part, and is tapered to the front to a tubular closed end. The tapered portion is bored radially to form two rows of three holes each. An internal striker is formed in the closed end and is integral with the body.

The inertia pellet is cylindrical with a solid closed base end. Externally, near the base, it is recessed circumferentially, and above th recess are two indents, diametrically oppo-sed, with partly accommodate the two balls.

The pellet contains 0.89 gram of C.E. and a capsule of detonating composition. The cop-per capsule is cup shaped with a hole in its base which is closed on its inside by a copper disk 0.003 inch thick. Above the disk is a composition weighing 0.026 gram, and consist-ing of mercury fulminate 22.0 percent, potassium chlorate 40.5 percent, anitmony sul-phide 33.6 percent and ground glass 3.0 percent. Above this composition is a pellet of mercury fulminate weighing 0.57 gram on top. The layer of TNT weighing 0.04 gram on top. The capsule is inserted in the inertia pellet open end first, and secured by turning the end of the pellet over the base of the capsule and varnishing the join.

A felt disk is inserted between the base of the inertia pellet and the fuze body.

The ferrule is cylindrical with an external circumferential recess about its center.

Near its forward end are two holes, bored diametrically opposite, which partly accommo-date the two steel balls. The ferrule surrounds the base end of the inertia pellet and is supported by the smaller of the two stirrup springs.

The stirrup spring is cylindrical; its lower edge has three external projections which fit under the ferrule and its upper edge has three internal projections which engages in the recess near the base of the inertia pellet.

The arming sleeve is cylindrical with a circumferential internal recess near its base edge. It surrounds the forward part of the ferrule and contains the two steel balls locking the inertia pellet in the safe position. The sleeve is supported by the larger stirrup spring.

The stirrup spring is cylindrical and split. Two lugs, cut diametrically opposite in its lower edge, project and fit under the arming sleeve.

ACTION:

Before Firing. The inertia pellet is locked and held away from the striker by the two steel balls which are retained by the arming sleeve.

After Firing. On acceleration, the arming sleeve sets back and is retained by the larger stirrup spring which engages the circumferential groove, thereby freeing the two balls which move outwards under centrifugal action. Creep action is prevented by the smaller of the two stirrup springs.

On impact or graze, the inertia pellet moves forward onto the striker and detonates its filling.

Figure 604 – 27/34 W. Z. 36