Use: Ordinary projectiles for 12-cm and 20-cm short guns.

Over-all length (with gaine): 6 1/8 inches.

Threaded length: 1/2 inch.

Number of threads: 6.

Construction: The fuze body is made in three sections and is fitted together with threads. The upper section houses the head of the striker. The mid-section houses the remainder of the striker and the five centrifugal wedges, which rest under a shoulder of the striker and prevent contact with the primer in the unarmed position. These wedges are surrounded and held in position by a split steel band. The primer is also housed in the midsection. The lower section contains the delay element and the selector switch, which is externally controlled. The instantaneous flash channel, when the fuze is set for delay action, is closed by a small steel plate (delay slide). When set for instantaneous action, the selector switch presents a recess allowing the delay slide, when centrifugal force sets in, to move out and free the instantaneous flash channel.

Operation: After the projectile is fired and begins to decelerate, the wedges are forced out by centrifugal force against a flat spring, thus freeing the striker. On impact, the striker is forced into the primer. The flash from the primer sets off a delay powder train, which in turn initiates the gaine. If the fuze is set for instantaneous action, the delay slide moves out with centrifugal force, leaving a flash channel to the gaine, which is ini-tiated directly.

Remarks: The setting of 0 to 5 seconds allows the projectile to sink approximately 25 meters before detonation.

Figure 437 – Type 88 Model 4 Instantaneous-Delay Fuze.