GENERAL: There are a large number of fuzes of this series which are designed for use with projectiles for a wide range of equipments. Some are designed for use with H.E. pro-jectiles and are normally fitted with an optional delay and ohter for use with smoke pro-jectiles and have no optional delay.

A.Z. 23 v (0.15) or (0.24)

The designation "A.Z. 23" is stamped above the flange of the aluminum body diametrically opposite delay setting plug. The period of delay is stamped adjacent to the plug in the form "V.O. 15". To obtain delay the slot in the head of setting plug is set coincident with the index marks letter "M" and "V". For action without delay the plug is set to the "0" in-dex.

EMPLOYMENT: This percussion fuze, with 0.15 or 0.25 secon delay, is used in the 105-mm howitzer and also in 75-mm separate ammunition. It is designed to function on im-pact or graze.

DATA:

Over-all length: 4.375 inches.

Maximum diameter: 2.375 inches.

Threaded length: 0.625 inches.

Number of threads: 4 RH.

CONSTRUCTION: The aluminum body of the fuze is in two parts. The head portion, which is screwed to the lower part, is solid and tapers towards the nose. A channel is formed through its center to accommodate the wooden hammer and the striker pellet. The channel is closed against air pressure at the top of a brass disc which is secured by a brass collar fitted around a stop formed in the nose of the fuze. The head is secured to the lower part by a fixing screw. (See fig. 577A.)

The lower portion of the body is tapered above the flange to correspond to the head and is screw-threaded below the flange for insertion in the shell. Near the top ot is reduced in diameter and screw-threaded to receive the head and it is recessed to accommodate the graze pellet. Another recess, formed in the base, contains the delay holder with a shutter and is screw-threaded to receive the magazine. The two recesses are connected by a central flash hole and an inclined flash channel. A radial channel for the optional de-lay assembly leads from the exterior to the lower recess.

The aluminum striker pellet, fitted with a steel striker, is supported above the graze pel-let by a creep spring and by five centrifugal aluminum segments pivoted on the top of the lower portion of the body. The segments are held between the base of the striker pellet and a shoulder on the graze pellet by an expanding spring ring.

The graze steel pellet carries an igniferous detonator supported by a perforated screwed plug.

The delay holder consists of a cylindrical aluminum pellet with a flash channel throught the center and a second channel, displaced from the center, which contains a delay fil-ling and conicides with the inclined flash channel from the recess containing the graze pellet. A slot formed in the top of the holder to receive the shutter extends to just be-yond the central flash channel. At the outer end of the slot the holder is recessed to re-ceive the inner end of a centrifugal bolt forming part of the shutter. A tin disk with per-forations corresponding to the channels in the holder is inserted above the holder.

The shutter assembly consists of a copper plate attached to a cylindrical bolt and is contained in the delay seting plug with a spiral spring which tends to retain the slutter in a position to close the central flash channel. The width of the shutter is greater than the diameter of the centrifugal bolt.

Figure 577A – A.Z. 23 (0.15)

The delay setting plug is recessed from the inner end to accommodate the centrifugal bolt and the spiral spring and has two slots to receive the sides of the shutter projecting beyond the bolt. The outer end of the setting plug is closed and has a groove for the setting key. The plug is retained in the fuze body by a screwed securing ring which en-gages a flange on the plug but does not prevent in being turned in setting.

The magazine contains a pressed perforated pellet of gunpowder weighing approximatley 2 grams and has a flash hole in the base closed by a paper disk.

ACTION: Before loading, the fuze is set for delay or nondelay action by means of the setting plug.

During flight, the coil of the expanding spring ring is enlarged and the segments swing clear of the graze and striker pellets by centrifugal force. The striker pellet is then held in the forward position by "creep" while the graze pellet is held back by the creep spring. The action of the shutter is governed by the setting plug. With the plug set to "0", the slot at is inner end are aligned with the projecting sides of the shutter and permit the centrifugal bolt to move outwards, taking with it the shutter and exposing the central flash channel in the delay holder. With the plug set in alinement with the "M" and "V" markings the slot in its inner end are not in a position to receive the protruding sides of the shutter. The movement of the shutter and bolt is thus prevented and the shutter re-mains closed.

On graze, the graze pellet moves forward, compressing the creep spring, and impinges the detonator on the striker. With suitable impact, the hammer and striker pellet are dri-ven in as the graze pellet moves forward and a more rapid action is obtained.

The flash from the detonator ignites the delay composition in the delay holder through the inclined flash channel and, if the shutter has opened, at the same time passes through the central flash hole and explodes the powder pellet in the magazine. With the fuze set for delay action, the central flash hole is masked by the shutter and the explo-sion of the magazine filling is brought about by the delay composition.

1. A.Z. 23/42 (0.15) This is similar to the A.Z. 23 v. (0.15), but is fitted with brass cen-trifugal segments and has an optional delay of 0.15 second.

2. A.Z. 23 v. (0.15) OR (0.25) Zn. This is similar to the A.Z. 23 v. (0.15) except that it is constructed mainly of zinc alloy. It is distinguishable be having a yellow tip.

3. A.Z. 23 v. (0.15) OR (0.25) Pr. This is similar to the A.Z. 23 v. (0.15) except that it is constructed mainly of plastic.

4. A.Z. 23. This is an early version which was constructed mainly of brass. It is fitted with an optional delay of 0.10 or 0.15 second.

5. A.Z. 23 (0.8). This is an early version which was constructed mainly of brass and is fitted with an optional delay of 0.8 second. It is fitted with a safety pin, which must be withdrawn before firing and prevents the centrifugal segements opening.

6. Kl.A.Z. 23 (0.2). This is constructed of aluminum and is of similar construction and operation to the A.Z. 23 v. It has an optional delay of 0.2 seconds and a noteworthy feature is that it is fitted with four centrifugal segments instead of the usual five. (See fig. 577B.)

Figure 577B – Kl.A.Z. 23 (0.12)

7. Kl.A.Z. 23 umg. The above fuze was found to arm too quickly when used in the follow-ing high velocity guns:

7.5-cm Pak 40, KwK 40 and 42

7.62-cm Pak 36 and Fk 39

This fuze was introduced to overcome this difficulty. On introduction, however, ist was found to be unsatisfactory and is to be replaced by kl.A.Z. 23/1.

In construction and operation, the fuze is similar to kl.A.Z. 23 (0.2).

8. Kl.A.Z. 23 (0.2) Pr. This is similar to kl.A.Z. 23 (0.2) but is constructed mainly of plas-tic.

The following fuzes are of the same gage as the A.Z. 23 v. (0.15), but they are designed for use with smoke shell and as a result are nit filled with an optional delay:

1. A.Z. 23 Nb. This is similar to A.Z. 23 v. execpt that there is no optional delay and also a safety pin passes through the body of fuze. (See fig. 577C.)

2. s.Jgr.Z. 23 Nb. This is similar to the s.Jgr.Z. 23 except that there is no optional delay.

Figure 577C – A.Z. 23 Nb