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Tail, Delay, Mk 237 Mod 0, Mk 238 Mod 0

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These fuzes differ only in the length of their arming stem. Delay arming is obtained by means of the 30-to-1 gear reduction system, which is like that of the Tail Fuze M115 Series. Upon completion of arming, the gear reduction assembly and the arming stem do not separate from the fuze, but cease rotation. Functioning time of these fuzes is determined by a lead shear wire (50% lead, 50% tin). The various delays are obtained by varying the diameter of the wire, i.e., increasing the diameter for longer delays. The slider carries a Detonator Mk 23, which is made up of three explosive components; namely, azide priming mixture, lead azide, and tetryl. The fuze incorporates a tetryl booster lead-in, but does not have an integral booster.

These fuzes incorporate an anti-withdrawal feature, but no booby trap device like the M123 series. Under normal handling and installation, the anti-withdrawal feature does not function, since the locking ball and its carrier arc held in place in the deep part of the eccentric groove, by a carrier pin and spring. Upon impact, however, the force of inertia is sufficient to withdraw’ the carrier pin from the fuze body, and allow the carrier spring to pull the hall carrier into the shallow part of the eccentric. locking the fuze in place. The fuze body is case-hardened to prevent removal with a wrench after impact. Since these fuzes require impact to lock in place, bombs with these fuzes can be safely returned to the base or carrier, and the fuzes removed for stowage.

Since these fuzes have a two inch thread diameter, it is necessary to remove the inner sleeve of the Adapter Booster M115A1 before installation. Fuzes should be screwed securely into the adapter booster; otherwise a dud may result. A special short-length locking pin is shipped with these fuzes for securing the Adapter Booster M115A1 to the base plate.

Bombs fuzed with these fuzes should not be released at an altitude lower than that specified by the Chief of Naval Operations as the minimum safe altitude of release for instantaneous action fuzes; for, if the bomb is subjected to multiple impact, the first impact would completely arm the fuze, and the second might shear the lead shear wire, allowing the fuze to fire without delay.

These fuzes are detonator safe. In the unarmed position, the detonator is lined up with the safety expansion chamber. If the detonator should function prematurely, the force of detonation is dissipated in this cavity, and will not set off the booster lead-in charge, or adapter booster charge.


No information about functioning.

Hazardous Components

No information about hazardous components.

See Also

Adapter Booster, M115, M115A1

Tail, Delay, M123, M123A1

Tail, Impact, M115


OP 1664, Volume 2 - US Explosive Ordnance (1947)

USNBD - Bombs and Fuzes, Pyrotechnics (1945)