USNBD, Bombs and Fuzes; Section III - Bomb Fuzes: M123A1, M124A1, M125A1

U.S.N.B.D. - UNITED STATES - BOMBS AND FUZES; PYROTECHNICS

SECTION III - BOMB FUZES

DATA:		U.S. ARMY TAIL FUZES
		M123A1, M124A1, M125A1
BOMBS USED IN
M123A1	AN-M30A1 100# G.P.
	AN-M57A1 250# G.P.
M124A1	AN-M64A1 500# G.P.	(SERVICE)
	AN-M58A2 500# S.A.P.
M125A1	AN-M65A1 1000# G.P.	CHEMICAL TIME
	AN-M66A1 2000# G.P.	ANTI-WITHDRAWAL
	AN-M59A1 1000# S.A.P.
	M103 2000# S.A.P.
FUNCTIONING	Chemical long delay fuze:
	delays of 1, 2, 6, 12, 24,
	36, 72, and 144 hours.
ARMED CONDITION	Considered armed if drop-
	ped, because of glass am-
	poule, or after 4 to 6 turns of the vanes.
FUZES USED WITH	None, though a nose anti-distrubance fuze is being developed
	to be use with it.
ARMING TIME	4 to 6 turns of the vanes.
VANE SPAN	5"
MAX. BODY DIAMETER
OVERALL LENGTH	M123A1 - 9.39"
	M124A1 - 12.39"
	M125A1 - 16.39"
MATERIAL	Zinc plated and dichromate coated steel.

GENERAL:

The only difference in these three fuzes is in the length of the arming stem. Longer bombs require longer arming stem so that vanes can catch the air slip from the bomb. The M123A1 series fuzes were developed to eliminate any possiblilty of premature firing resulting in aerial bursts, which sometime occured in the unstaked M123 series. Essent-ially, 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 M19A2 Detonator contains primer mixture, lead azide, and tetryl.

OPERATION:

When the arming wire is withdrawn, the vane assembly starts to rotate, causing ro-tation of the clip hub, clip, and arming stem. After about 4 to 6 turns of the vanes, the arming stem moves inward far enough to break the ampoule. Approximately 5 to 6 addi-tional turns are sufficient to seal fuze, i.e., stem collar is flush against rubber reatiner washer. Balance of operation is same as the M123 series (See page 199).

REMARKS:

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

(b) Before the M123A1 series was in production, existing stocks of M123 series fuzes on hand in this country were modified; the stem cup was utilized without the gear re-duction assembly, and a vane hub, clip hub, clip, safety catch, and 8 bladed vane in-stalled (Designated M123A1 series).

(c) More rigid specifications and factory inspection tests were instituted on later lots of the M123 series ampoules, and are being carried out an the M123A1 series also.

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

(e) 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 ace-tone or alcohol-acetone solution has been acting, or if the fuzes are in an unarmed condition.

(f) Before to "Remarks" covering M123 series (page 199), items (a) to (e) inclusive listed, apply to the M123A1 series also.