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FUZE, POINT DETONATING : M78 SERIES |
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Filler and Weight | ||
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| NA, 0 | |||
| Body and Overall Weight | |||
| NA, 2.09 lb | |||
| Color | |||
| NA | |||
| Type of Round, DODIC | |||
| PD, 1390 -N330 |
| Description: |
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| The fuze has a solid hardened steel body with an ogival nose. A well in the base houses a firing pin and an inertial-type delay plunger mechanism containing a detonator. The delay plunger in each type is locked by two spin- activated, spring-loaded plunger pins. All M78 series fuzes are equipped with Booster M25, designed solely for this fuze. The booster has an externally threaded body containing a delayed arming mechanism, Detonator M17, and tetryl booster lead charge. The delayed arming mechanism is an eccentric, spin-activated rotor containing the detonator. In the unarmed position, the detonator is out of line with the flash hole and the rotor is locked by a springloaded centrifugal lock pin, which is in turn locked by a setback pin. The base of the booster is an aluminum cup threaded onto the body and containing a 340-grain tetryl booster charge. As issued, Booster M25 is packed and shipped with, but not attached to, the fuze. Fuze M78 has a delay plunger with a single 0.025 second delay. Fuze M78A1 is supplied with a non-delay Plunger Assembly M1, or a 0.025 second delay Plunger M1. Fuzes preset for non-delay are intended primarily for spotting, and are identified by a white-painted nose. |
| Use: |
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| Point detonating fuzes of the M78 series are constructed especially for use in spotting and destruction of concrete targets. The fuzes are used with HE projectiles fired from guns and howitzers in calibers 75mm through 8-inch, except 175mm. |
| Functioning: |
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| Upon weapon firing, setback force withdraws the setback pin from the lock pin. As the spin rate of the projectile increases, centrifugal force withdraws the two plunger pins from delay plunger Assembly Ml in the head of the fuze, thus arming the delay plunger. Simulta neously, centrifugal force withdraws the lock pin, permitting the rotor to turn on the pivot pin until Detonator M17 is aligned with the flash hole in the booster top cover. The rotor is locked in the armed position by the centrifugal lock pin for the remainder of the flight. This delayed arming of the booster mechanism provides bore safety. Upon impact, Delay Plunger M1 is driven forward by inertia into the firing pin to initiate the explosive train. |
| Munition Components: |
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| Data Source: |
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| TM 43-0001-28 |
| Munitions Tech Data Sheet: |
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