Conversion of M203 and M203A1 charges

M203 and M203A1 charges: description and tabular data

Charge M203 (red bag), zone 8S

Description. A charge that cannot be configured, a “red bag” about 768 mm long. It contains approximately 11.8 kg of M30A1 high-energy propellant in a bag. A red igniter pad with 28 g of black powder is sewn to the base.

A central igniter tube runs almost the full length through the centre of the charge: a nitrocellulose paper tube with a small bag of black powder, sewn to the main igniter.

The front end of the charge is lined with a liner: one side is fabric impregnated with titanium dioxide and wax, the other is lead.

Four tie straps sewn to the base run along the charge and are tied at the front end. Under the straps at the front end is a doughnut-shaped flash suppressor. A cylindrical jacket is put over the charge and tightly laced. This lacing gives the assembled charge the necessary rigidity and structural stability, which is also what distinguishes the 8S charge from the zone 8 charge M119/M119A1.

Characteristics:

• length up to 768 mm;
• diameter up to 156 mm;
• M30A1 propellant about 11.8 kg,
• web thickness 2.0 mm;
• main igniter pad with 28 g of black powder;
• igniter tube with 113 g of black powder;
• moulded nitrocellulose tube; lead foil 156 g;
• additive of 496 g of titanium dioxide with wax;
• M3 flash suppressor;
• cardboard cap.

Function. The flash of black powder in the M82 percussion primer ignites the pad at the base of the charge. The igniter pad in turn ignites the black powder, and ignition spreads to the propellant charge. The gases expanding rapidly from the propellant charge give the projectile a velocity sufficient to hit the target. The flash suppressor reduces the blast-wave overpressure and the flash in the gun barrel.

Tabular data: charge M203

Temperature limits

Restriction. The M203 charge must not be stored or transported in a vertical position: this may damage the igniter tube.

Charge M203A1 (combustible case), zone 8S

Description. A propellant charge that cannot be configured, about 768 mm long. Its design includes 12.7 kg of M31A1E1 tubular propellant and a base igniter pad built into the rigid end cap of the combustible cartridge case.

The igniter pad contains 20 g of black powder and 28 g of CBI. The combustible cartridge case is made of nitrocellulose kraft paper, a stabilizer, a resinous compound and additives that reduce barrel wear. There is also a lead foil liner (to prevent coppering) and anti-wear additives.

Function. The flash of black powder in the M82 percussion primer ignites the pad at the base of the charge. The igniter pad burns and ignites the propellant charge. The gases expanding rapidly from the propellant charge give the projectile a velocity sufficient to hit the target.

Differences between the models. The M203A1, like the M203, is an 8S propellant charge developed for the extended range of long-barrel 155 mm howitzers. It consists of one module of tubular propellant and a main igniter pad in a full-size rigid combustible case with an end cap.

The charge also contains an anti-wear additive and lead foil against coppering. The base M203 is a “red bag” charge with a central igniter and granular propellant. The M203A1 burns “cooler”, which increases gun barrel life and reduces flash and blast wave.

Tabular data

Temperature limits