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TM 43-0001-28

FUZE, POINT DETONATING: M557

Type Classification:

Std AMCTC 5726 dtd 1967.

Use:

Point Detonating Fuze M557 is a selectivesuperquick or 0.05 second delay impact fuzedesigned for use in ammunition for guns of75mm through 155mm, for rifles of 75mm and105mm, for howitzers of 75mm through 8-inch,and for 4.2-inch mortars.

Description:

The M557 fuze consists of Fuze M48A3assembled with the M125A1 booster. The fuzePD head assembly contains a firing pin held inposition by a firing pin support which preventsinitiation of Detonator M24 until impact. Thefuze body contains an M1 delay plunger assem-bly and an interrupter assembly with a settingsleeve which provides a means of setting or

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TM 43-0001-28

feet, depending upon the weapon and chargebeing fired.

Functioning:

Upon firing, centrifugal force is utilized toarm the fuze. Centrifugal force retracts thedetents holding the rotor in the unarmed posi-tion allowing it to turn against the gear trainmechanism which controls the turning speed ofthe rotor until the rotor is in the armed posi-tion. Once in the armed position the rotor islocked in position by a spring loaded pin andthe Rotor M17 detonator is aligned with the det-onation train of the fuze. Simultaneously,centrifugal force will arm the M1 delay plungerof the fuze and retract the flash tube inter-rupter unless the fuze is set delay, in whichinstance, the flash tube interrupter will notretract and the flash from the nose superquickelement will be prevented from initiating theexplosive train of the booster. The fuze is initi-ated upon impact with the target; the firing pinof the fuze head assembly is driven into the

M24 detonator which flashes through to theM17 detonator activating the lead charge andbooster pellet. If set delay the flash tube isblocked mid the M17 detonator is activated bythe delay element. The delay mechanism of thebooster provides an arming distance of approxi-mately 200 feet, depending upon the weaponemployed.

TM 9-1300-251-20

SC 1340/98-ILSB 700-20TM 9-1015-203-12TM 9-1015-234-10TM 9-1025-200-12TM 9-2300-216-10TM 9-2350-311-10

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