120 mm APFSDS-T M829A1, M829A2 and M829E3

were development models. It was used operationally during Operation Desert Storm, when it received the name `Silver Bullet'. The M829A1 has been out of production since the end of 1993, by which time over 177,000 had been manufactured . An M829A2 version, produced solely by PRIMEX Technologies (now General Dynamics, Ordnance and Tactical Systems (GD-OTS)) was type classified during 1992 and entered low-rate production during 1993. In June 1995, a firm fixed price contract was placed with GD-OTS for the manufacture of 23,278 M829A2 rounds. The order was worth US$5.5 million. The M829A2 is the primary anti-armour 120 mm tank ammunition in service with the US Army. By the beginning of FY98 total procurement had reached 106,000 units. The total for FY98 was 20,000, followed by 3,000 in FY99. The final batch order during FY00 was for 7,000. An M829E3 model was introduced with the objectives of reducing sabot parasitic weight by 20 per cent and increasing muzzle velocity by 10 per cent, both compared to the M829A2. The then PRIMEX Technologies and Alliant Techsystems (ATK) competed for the contract which was awarded to ATK in August 1998. The contract was worth US$30 million and related to the engineering and development of the M829E3. The contract, plus two subsequent production orders, could bring the total contract value to US$127 million by the year 2004. It is intended that the M829E3 will replace all existing M829 models in service with the US armed forces. Compared to past procurements of similar rounds, the number of M829E3 rounds is expected to be limited as it is regarded as an interim response to the arrays of reactive and other armours expected to appear in coming years. Full production, for 5,000 rounds, will commence during FY02, with 5,000 units each year from then onwards until (and including) FY05. For the M829E3 development programme, which will lead to the eventual M829A3, ATK have teamed with Armtec Defense (combustible case), Aerojet GenCorp (DU penetrator) and American Ordnance (loading and packing). ATK's Conventional Munitions Group will carry out design and programme management from its Hopkins, Minnesota, facility. Propellant will be supplied by the Radford Army Ammunition Plant in Radford, Virginia. The Alleghany Ballistics Laboratory, Rocket Center, West Virginia, will fabricate the discarding sabot, together with Alliant's Ferrulmatic Operations in Totowa, New Jersey. The primer and tracer will be prepared at Alliant's Kilgore Operations in Toone, Tennessee. Load and pack operations will be carried out by American Ordnance at the Iowa ammunition plant. It is understood that consideration of a M829E4 variant is in progress. This will probably have an anti-reactive armour capability. Description The 120 mm M829A1 APFSDS-T round is fixed with the projectile assembly secured to the Combustible Cartridge Case (CCC) by a case adaptor ring. The CCC has a steel stub cartridge case base with a silicone rubber sealing ring around the top. An M129 electrical primer is secured to the cartridge case base. The M829A1 subcalibre Depleted Uranium (DU, also known as staballoy) finned projectile weighs 8.165 kg and is described as being redesigned compared to the projectile used with the M829. The projectile has a high length-to-diameter ratio, a steel windshield and is carried in a three-piece aluminium sabot. The length to diameter ratio is 30.4:1 and a diameter of 22 mm . The M829A2 projectile has a revised composite material sabot construction providing a 30 per cent reduction in parasitic weight; it is the first production design to incorporate this innovation. The M829A2 fin assembly is aluminium. With the M829A1 the CCC contains 7.9 kg of JA-2 `solventless' granular multiperforated (19 perforations) propellant in six containment bags, these prevent spillage in the event of a rupture of the combustible case walls. With the M829A2 the CCC has granular JA-2 propellant packed around the base of the insulated M129 primer assembly but the bulk of the propellant load is JA-2 `KERFED' in stick form, total weight being 8.7 kg. On both models case ignition does leave the steel base stub intact for ejection from the gun after firing. An M129 primer is used on both models, with the minimum firing current being 1.25 A at 24 V . For the M829E3, the propellant load of the round will be increased by a process known as the 'propellant pie configuration'. For this propellant slabs or discs arranged around the primer tube and penetrator and perforated to regulate the burn rate. This packing method permits a propellant density increase inside the case of about 25 per cent compared to a normal load. A propellant weight of about 11.3 kg has been forecast. 120 mm APFSDS-T M829A1