(Fig. 6)

The A.Z. 23 umg. fuzes differ externally from the A.Z. 23 fuzes in having a much shorter coned head and are longer between the flange amd the base. This lower part which en-ters the fuze hole in the shell, has only a few screwthreaded below the flange, the re-mainder being plain. Three types of the "umg." fuze have been found. These are:–

A.Z. 23 umg. 0,8

A.Z. 23 umg. m. 2 V.

A.Z. 23 umg. 0,15

The "0,8" fuze with an optional delay of 0.8 of a second, and originally used for 15 cm Gr. 19 for the 15 cm medium howitzer s.F.H. 18, is described in Pamphlet No. 1. This descrip-tion was based on a French report. Fuzes of this type of later manufacture are made of steel with a rustproofed surface.

The "m. 2 V." fuze is also an optional delay fuze with two alternate delays. Details of the fuze are not yet available. Both this and the "0.8" fuze are being replaced by the "0.15" fuze.

The "0.15" fuze with an optional delay of 0.15 of a second is here described and differs from the later type of "0.8" fuze only in the time of the delay.

Each of these fuzes can be identified by the designation stamped above the flange. The "m. 2 V." and more recently the "0.15" fuze are used in the H.E. shell, "15 cm Gr. 19" for the 15 cm medium howitzer s.F.H. 18 and in the H.E. shell "21 cm Gr. 18" for the 21 cm howitzer 21 cm Mrs. 18. The weight of fuzes of this type is approximately 1 lb. 10 oz. 2 drs.

The A.Z. umg. 0.15 has the usual combined D.A. and graze mechanism consisting of a steel graze pellet carrying the detonator and an aluminium needle pellet held apart by a creep spring and five brass centrifugal segments encircled by an expanding spring ring. The graze pellet is contained in a central recess in the body which has two flash chan-nels at the base. One channel leads direct to the magazine through an open channel in the delay holder, the other leads to the magazins through the delay composition in the delay holder. The needle pellet with a steel sleeve surrounding it and a wooden hammer above it is carried in the head of the fuze. The steel head is retained in the body by a retaining ring which screws into the top of the body and engages an external flange near the lower part of the head. The circumferential rim at the bottom of the head varies in depth to act as a cam which position the spring loaded locking bolt of the shutter. Thus when the head is rotated to bring the deepest portion of the rim over the locking bolt the bolt is pressed down into the radial recess containing the shutter in the lower part of the fuze and prevents the shutter from opening. The setting positions of the head are marked on its protruding part by two line at right angles which are set to an index line on the retaining ring and body. The setting line for delayed action is marked "MV" and that for "non-delay" "OV".

The delay holder, shutter assembly and magazine are all of the same type described for other fuzes of the A.Z. 23 type.

The fuze is set for "delay" or "non-delay" by turning the head to bring the appropriate setting marking into coincidence with the index line. When set to "MV" the locking bolt is pressed down by the deep part of the rim at the bottom of the head and locks the shut-ter in the closed position. When set to "OV" the short part of the rim is over the locking bolt thus permitting the bolt to be raised clear of the shutter recess by its spring.

During flight the coil of the expanding spring ring is enlarged and the segments swung clear of the graze pellet by centrifugal force. It set for "non-delay" the shutter is also thrown outwards and the open flash channel in the delay holder is exposed. Forward mo-vement of the graze pellet is prevented by the creep spring.

On graze the detonator is carried forward by the graze pellet and pierced by the needle. When suitable impact is obtained the hammer and needle pellet are driven in as the graze pellet move forward, thus accelerating the action. With the head set for "non-delay" the flash from the detonator passes direct to the magazine. If set for "delay" the open chan-nel in the delay holder is masked by the shutter so the flash has to burn through the de-lay composition to reach the magazine.

Fig. 6