Fig. 14

Fig. 14 shows the principal features of a German 10.5 cm H.E. shell fitted with one driv-ing band and a percussion fuze AZ 23 with 0.25 in delay.

The shell is streamlined and fitted with a screwed-on head. The driving band consists of an inside portion of mild steel or iron and an external portion of copper. The method used to prevent the band slipping round the body of the shell is by simple knurling. The adhes-ion of the copper to the iron is so good that twisting of the band on firing does not cau-se any separation between the two metals. The reason is not clear whether the two-metal driving band is due to shortage of copper or as a remedy for the tearing driving of driving bands.

The shell filling is probably T.N.T. In some case the filling is effected by pouring, the shell being protected internally by varnish, and in other cases by block charges, each contai-ned in a carton cover, a plastic substance being used to make a joint between the co-vers and internal surface of the shell. The shell is filled up to the level of the ring secur-ing the exploder container.

The steel exploder container is secured by means of a steel securing ring, the inner thread of which is screwed to the container, and the outer thread to the fuze hole of the shell. These two components are treated externally with a protective coat of black preservative the nature of which is not specified.

An exploder of PICRIC ACID contained in a cylindrical casting of tinned brass fits into the container.

The detonator containing the cap is housed in the upper part of this casting. The deto-nator consists of a small copper thimble pierced by five holes (nature of filling not sta-ted). The thimble is closed by a washer, the central hole of which is closed by a paper into the edge of the cylindrical brass casting.

Fig. 14

The driving bands of certain projectiles of 105 and 150 mm, are in some of copper only and in this case the method used to prevent the band slipping is in the form of a checker pattern.