M123A1, M124A1, and M125A1 (Tail Chemical Time, Anti-Withdrawal)

Bombs

Armed condition

Fuzes used with

Arming time

Vane span, inches

Over-all length, inches

Material

Zinc-plated and dichromate-coated steel

General: The only difference in these three fuzes is in the length of the arming stem. The M123A1 series fuzes were developed to eliminate any possibility of premature firing resulting in aerial bursts, which sometimes occurred in the unstaked M123 series. Essen-tially, the M123A1 series differs from the M123 series in that the gear-reduction system has been eliminated, and a direct-drive arming system has been installed. Functioning time in these fuzes is determined in the same manner as the M123 series. The Detonator M19A2 contains the primer mixture of lead azide and tetryl.

Operation: When the arming wire is withdrawn, the vane assembly starts to rotatem causing rotation of the clip hub, clip, and arming stem. After about four to six turns of the vanes, the arming stem moves inward far enough to break the ampoule. Approxima-tely five to six additional turns are sufficient to seal the fuze; i.e., the stem collar is flush against the rubber retainer washer. The balance of the operation is the same as the M123 series.

Remarks: Prior to the development of the M123A1 series, the M123 series with gear reduction was modified by pinning the body extension of the fuze to the body by use of gear of two steel shear pins to prevent premature firing (aerial burst being caused by the torque developed by the gear-reduction system after sealing). Kits were also provided for installing these shear pins in the field.

Before the M123A1 series was in production, existing stocks of M123 series fuzes on hand in this country were modfied; the stem cup was utilized without the gear-reduction assembly, and a vane hub, clip hub, clip, safety catch, and eight-bladed vane installed. This was designated the M123A1 series.

The fuzes of the M123A1 series, as well as the later M123 series lots, do not have the solvent dyed in various colors. Dye particles entered pores of the ampoule glass at the sealing point, increasing the possibility of breakage and leakage.

In the M123A1 series, if the body extension is backed off approximately 3/32 of an inch from the body, fuzes are activated, regardless of the length of time the acetone or alcohol-acetone solution has been acting, and regardless if the fuzes are in an unarmed condition.

Modification: The M123A1 series was modified, adding an ampoule-retainer sealing cup made of gliding metal, a sealing washer, set screw, and lock nut. This modification assures more effective sealing, since the arming screw crushes (but does not break through) the ampoule-retainer selaing cup. The set screw and lock nut hold the ampoule retainer in place and assure a tight fit against the retainer cup.

Figure 344. Tail Time Fuze M123A1