M123, M124, and M125 (Obsolescent) (Tail Chemical Time, Anti-Withdrawal)

Bombs

M123

M124

M125

Functioning

Armed condition

Fuzes used with

Arming time

Vane span, inches

Body diameter, 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. Functioning time is determined - for the 1-, 2-, 6-, and 12-hour delays - by varying the concentration of the alcohol-acetone solution, and for the 24-, 36-, 72-, and 144-hour delays, by varying the thickness of the celluloid disc (thickness increases as delays in-crease). The Detonator M19A2 contains the primer mixture of lead azide and tetryl.

Operation: The stem case and gear system of these fuzes are identical to the fuzes in the AN-M100A2 series, except that the threads on the arming stem are right-hand threads and thread downward instead of out. The pinion gear revolves around the statio-nary gear, and, in so doing, rotates the movable gear (which has one more tooth than the stationary gear) one tooth per revolution. Since the arming stem is secured to the movable-gear sleeve, it also rotates counter-clockwise, threading down toward the glass ampoule. The arming stem exerts pressure on the ampoule cap, causing the glass am-poule to break where it rests on seat disc and knife edge. Attached to the arming stem is a stem collar, which compresses a rubber washer to seal the upper part of the fuze from leakage (344 - 387 revolutions of vanes to seal). In the 1-, 2-, 6-, and 12-hour de-lays, the acetone or alcohol-acetone solution is freed to act on the celluloid ring retain-ing the locking balls. In the 24-, 36-, 72-, and 144-hour delays, the acetone is freed to act on the celluloid disc and subsequently the celluloid ring retaining the locking balls. As the acetone or alcohol-acetone solution acts on the celluloid ring, the locking balls are forced out by the head of the screw which is threaded into the spring-loaded firing pin. After the predetermined delay, as effected by varying the thickness of the celluloid disc, the balls will be forced clear of the screw head and the firing pin will strike the detona-tor.

If an attempt is made to withdrawn the fuze once it has been installed, the anit-with-drawal locking ball will ride into the shallow part of its groove, and lock the lower fuze body to the adapter booster. Further turning of the fuze will merley unthread the upper fuze body from the lower part, allowing the spring-loaded firing-pin sleeve force the slee-ve balls into the separation, driving both the sleeve and the firing pin toward the detona-tor. A separation of 3/64-inch activates the fuze, regardless of the length of time the acetone or alcohol-acetone solution has been acting, or if the fuze is an unarmed condi-tion. Later lots require 1 1/2 turns or 3/21 inch to activate.

Remarks: Never attempt to withdraw the fuze during of after installation in the bomb. If the bombs with this fuze are not dropped, they must be jettisoned over enemy territory or in the sea. They cannot be considered safe, even if dropped unarmed.

The fuzes should not be subjected to temperatures exceeding 120° F. (High tempera-ture may damage the celluloid ring.) In the packing box are two vials of powder - one a green-stoppered vial, the other a red-stoppered vial. If the temperature exceeds 150° F., the powder in the green-stoppered vial will melt or solidify, and the fuzes are not to be used for low-altitude bombing. If temperature exceeds 170° F-, the powder in the red-stoppered vial will melt or slidify, and the fuzes must be destroyed.

Before inserting the fuze in the bomb, gage the adapter-booster cavity with the plug gage provided in each box of fuses. Any bomb with which difficulty is experienced in in-serting this gage, must not be fuzed with these fuzes.

Later lots of these fuzes are equipped with new-type lock nut as on the M123A1 series.