USNBD, Bombs and Fuzes; Section III - Bomb Fuzes: AN-M120A1, AN-M120, M170

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

SECTION III - BOMB FUZES

DATA:		ARMY-NAVY NOSE FUZE
		AN-M120A1 M170
BOMBS USED IN
AN-M102A1	AN-M40A1, AN-M40, M72A1
	para-frag.; M71A1 and
	M73A1 practice; M86	MECHANICAL IMPACT
	120 lb. frag.	with
M170	AN-M40A1, AN-M40, M72A1	MECHANICAL ARMING DELAY
	para-frag.; M71A1 and
	M73A1 practice
FUNCTIONING	Instantaneous
ARMED CONDITION	When arming pin is out.
FUZES USED WITH	None
ARMING TIME:

AN-M102A1	1.9 (± .15) sec. mechanical delay
M170	1.5 (± .15) sec. mechanical delay
MAX. BODY DIAMETER	2.2"
OVERALL LENGTH	4.4"
MATERIAL	Aluminium alloy body, cadmium plated striker and striker head.

GENERAL:

The M170 duplicates the AN-M120A1 in all respects except for the arming time which is shortened to 1.5 (± .15) seconds.

OPERATION:

As the parachute opens, the arming wire is withdrawn from the arming pin, which is then ejected by the arming pin spring. Ejection of the arming pin frees the arbor, a semi-circular projection on the timing shaft, to be rotated by the clockwork mechanism. A regulator controls the oscillation of the clockwork governor, and is properly adjusted at the factory. The slider pin rides against the inside of the arbor under pressure of the slider spring. After the arbor has been rotated a full 160°, it clear the slider pin, allow-ing the slider to be forced across the fuze by the slider spring, lining up the detonator with the firing pin. A spring-loaded detent locks the slider in position. On impact, the striker head is forced in, driving the firing pin into the primer.

REMARKS:

The M120 and AN-M120 did not have the clockwork regulator, and had an arming time of 2.5 (± .25) seconds; hence, attacks had to be made at higher levels. External appearance of all designs is the same.

This fuze is replacing the AN-M104 in the parachute fragmentation bomb.

The AN-M120 was a replacement for the AN-M104 in the parachute fragmentation bombs.

The M170 is designed to supplant the AN-M120A1 in all bombs receiving the AN-M120A1, except for the M86 para-frag, which will contains to use the older fuze.