USNBD, Bombs and Fuzes; Section III - Bomb Fuzes: M112A1, M113A1, M114A1

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

SECTION III - BOMB FUZES

DATA:		U.S. ARMY TAIL FUZES
		M112A1, M113A1, M114A1
BOMBS USED IN
M112A1	AN-M30, 100 lb. G.P.
	AN-M57, 250 lb. G.P.
M113A1	AN-M43, 64, 500 lb. G.P.	(Service)
	AN-M58 500 lb. S.A.P.	MECHANICAL IMPACT
	M32, 600 lb. G.P.	PYROTECHNIC DELAY
M114A1	AN-M44, 65, 1000 lb. G.P.	(For Skip or Masthead bombing
	AN-M58, 1000 lb. S.A.P.	from land-based plan only)
	M33, 1100 lb. G.P.	M112, M113, M114
	AN-M34, 66, 2000 lb. G.P.	(Obsolescent)
	M103, 2000 lb. S.A.P.
FUNCTIONING	M16A1 primer detonators
	with 4-5 or 8-15 seconds
	delay are interchangeable.
	(Masthead, skip bombing).
ARMED CONDITION	When vane assembly has risen .75 in.
FUZES USED WITH	None
ARMING DATA	18-21 vane revolutions; 100 ft. air travel
VANE SPAN	5 in.
MAX. BODY DIAMETER	1.5 in.
OVERALL LENGTH	M112A1, 9.6 in.
	M113A1, 12.6 in.
	M114A1, 16.6 in.
MATERIAL	Cadmium plated steel.

GENERAL:

The only difference in these three fuzes is in the length of the arming stem. Larger bombs require a longer arming stem so that the vanes can catch the air slip from the bomb.

OPERATION:

As the vanes rotate, the arming stem is unthreaded from the plunger. There are no reduction gears in the vane assembly, the arming stem being secured to the vane nut by a cotter pin, and 18 to 21 revolutions of the vanes will free the plunger. A key pin riding in a groove in the plunger prevents it from rotating as the arming stem is with-drawn. On impact, the plunger compresses its creep spring and the spring-loaded firing pin forces the locking balls out into the enlarged part of the fuze cavity, freeing the firing pin. The cocked firing pin spring forces the firing pin against the primer, initianting the delay in the primer detonator.

EARLY DESIGN:

The original M112, M113, and M114 used the M16 primer detonator, which is the same as the M16A1 except that the shoulder is lower. Hence, when the M16A1 was designed it was necessary to alter the base of the fuze slightly to permit use of this primer detonator with the higher shoulder on its external surface. The alternative M16 primer detonators had delays of 4-5 or 8-11 seconds, whereas the longer delay M16A1 has a range of from 8-15 seconds. This delay consists of a barium chromate silicon powder in place of the lead chromate silicon mixture used in the M16 primer detonator. The M16, though no longer being manufactured, can still be used in the M112A1, M113A1, and M114A1 fuzes.

REMARKS:

This fuze will funciton on impact angle of 3°, and gives positive action because of its cocked firing pin. This fuze is unsafe for carrier landings. Delay of 4-5 seconds should be used against sea targets, and delay of 8-15 seconds against land targets.

NEVER TURN THE VANES COUNTER-CLOCKWISE TO RENDER FUZE SAFE, AS THE ARMING STEM MAY DEPRESS PLUNGER INSTEAD OF ENGAGING IT.

These fuzes may have a groove around the top of the fuze body (as in drawing) or the top may be straight like the M123 series fuzes (see page 199). This groove is a distingushing mark used by those manufactures making both the M112 and M123 series fuzes, and is not to be considered a positive mark for fuze identification.