Description
This cartridge is a high explosive round designed to inflict personnel casualties from ground burst effect, and is fired from 40mm Grenade Launcher M79 or the M203 (attached to the M16 series rifle).
The cartridge is a fixed round of ammunition consisting of a projectile assembly and a cartridge case assembly. The projectile has a hollow, one-piece aluminum body containing rotating bands. A hollow aluminum ogive is fitted to the front end of the projectile. A hollow steel ball assembly containing the bursting charge is fitted into the rear of the projectile body. A booster charge with a PD fuze is threaded into a well in the forward side of the ball. The projectile assembly is press-fitted into a cartridge case. The case is a hollow, aluminum bichambered cylinder with an annealed brass propellant cup fitted into the cartridge base. The cup contains the propelling charge with a percussion primer in the center. The cup acts as a high pressure chamber and the hollow cavity in the case, which surrounds the cup, acts as a low pressure chamber. The fuze contains an inertial ring operating through push pins and levers upon a detonator.
Do not pick up or otherwise disturb a fired projectile, since the fuzes incorporate a graze-sensitive feature.
Functioning
The weapon firing pin strikes the percussion primer igniting the propelling charge in the high-pressure chamber. The burning propelling charge generates sufficient pressure to rupture the propellant cup forcing the expanding gases through vent holes into the low pressure chamber. The rotating band around the projectile engages the rifling in the launcher tube to impart spin of 3600 RPM to the projectile. The pressure created by the expanding propellant gases in the low-pressure chamber forces the projectile through the launcher barrel with a muzzle velocity of 76 meters per second (250 fps). Setback force from firing causes the firing pin in the fuze to be withdrawn from the rotor ball detent, and centrifugal force from projectile rotation causes the rotor ball assembly to align the detonator with the explosive train. The fuze arms after the projectile has traveled approximately 2.4 to 3 meters (8 feet) from the launcher. Upon graze or impact with the target, inertia causes the inertial ring to act on the push pins, pivoting the levers inward to force the firing pin into the detonator. The detonator ignites the booster charge, and the booster detonates the explosive charge, producing blast and fragmentation of the projectile body.
Hazardous Components
Filler - Comp B (32 g, 1.14 oz)
M118 cartridge case
Propellant - M9 (330 mg)
Primer - Percussion, M42
See Also
Source(s)
TM 43-0001-28, Artillery Ammunition (chg 11, 2003)
TM 9-1385-51, Ammunition (Conventional) for Explosive Ordnance Disposal (1967)
