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Type Classification:

Std AMCTC 3325 dtd 1965.

Use:

Base Detonating Fuze M578 is used with HEP ammunition fired from 105mm gun cannons,

Description:

The fuze has a steel body. A steel impact ball is housed in the rear of the fuze body. A spring-loaded striker assembly containing the firing pin is located just forward of the impact ball and is locked when in the unarmed position by setback pins and a spin-activated locking segment. The detonator and escapement mechanism are carried in a spin-activated delayed arming shutter ahead of the striker, and are out of line in the unarmed condition. The booster lead charge and RDX booster charge are contained in a booster cup threaded into the forward end of the fuze body. Earlier models have slightly different exterior configuration.

Functioning:

The fuze becomes armed when centrifugal force from projectile rotation moves the locking segment to the armed position (6000 to 8500 rpm), thus releasing the striker assembly, and moves the delayed arming shutter to align the detonator with the firing pin (7000 to 8500

rpm). This delayed arming provides a safety distance from the muzzle of at least 26 feet. Upon either impact or graze, the impact ball drives the striker and firing pin forward into the detonator. The detonator flash fires the booster lead charge and the booster charge to detonate the projectile.

Tabulated Data:

Thread size-------------------------- 1.8 in.-12UNS-

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