Shell, 155 mm, Illuminating DM 106

mm 155/39 TM; RDM 155 mm M139 and M114/39 ; SANTA BARBARA 155 mm SB 155/39 and 155/52 APU SBT-1 Howitzers, M114 155/45 and M114/39 ; Bofors FH-77B ; M199 Cannon for M198 Towed Howitzer; XM777 Lightweight Towed Howitzer. Development The 155 mm Illuminating DM 106 projectile is one of the three 155 mm projectiles developed as a result of the tripartite agreement entered into by Germany, Italy and the UK, to develop the 155 mm FH-70 Towed Howitzer and its associated ammunition. The 155 mm Illuminating DM 106 projectile is a Rheinmetall W & M GmbH (now Rheinmetall DeTec) development while the illuminating body was developed by the Italian Simmel SpA, now Simmel Difesa SpA. Description The 155 mm Illuminating DM 106 is a separate loading, base ejection carrier shell with a high-grade forged steel body. Normally fitted with a nose-mounted mechanical time fuze, the 155 mm Illuminating DM 106 uses the same carrier shell and booster as the 155 mm Smoke DM 105 (see separate entry). The interior, however, is occupied by a steel case containing an illuminating unit, the main parachute and a secondary spin retarder, all maintained in position by a base cover secured by six shear pins; the base cover also contains a drag parachute. A primary spin retarder is fitted to the dome-shaped top of the steel case along with an ignition chain unit. In operation, the nose-mounted time fuze functions, ideally at a height of approximately 600 m above ground level, and lights the booster which, in turn, lights the ignition chain unit. The ignition chain consists of a 90 g primary charge of black powder plus a 16 g secondary black powder charge. The 90 g primary charge creates an internal pressure which causes the six slotted pins in the recessed base to shear, allowing the shell's contents to eject. The drag parachute immediately deploys along with the four fins of the primary spin retarder which flip out under centrifugal forces. This reduces the spin rate of the steel case containing the illuminating body and main parachute. The second stage of deployment then commences approximately 3.5 seconds later when a delay composition ignites the 16 g secondary black powder charge. The pressure forces off the base cover once the six shear pins rupture and the main parachute is then free to deploy, along with the secondary spin retarder. Both combine to stabilise the illuminating body which is ignited by flash from the secondary charge. The illuminating body descends at a rate of less than 5 m/s and provides a non-flickering light intensity of not less than 1.8 Mcd over a diameter of 800 m. Minimum illuminant burn time is 60 seconds. The charge system used with the tripartite family of 155 mm ammunition is known colloquially as the `three cartridge' system. As its name implies the system is made up of three cartridges, the first two with a base charge and a number of increments. Cartridge 3 (Charge 8) is a unitary charge. Cartridge 1, the Charge Propelling, 155 mm, Howitzer, Charge 2, L2A1 consists of the Charge 1 and Charge Propellant Increment 2 combined to form Charge 2. The two weigh 1.21 kg and use SC/202 propellant. They are stitched together and should not be separated. Charge 1 L1A1 consists of a salmon pink cloth bag, containing 783 g of propellant SC/Z008 with an Igniter L19A1 containing 67 g of NC/200 and 18 g of G20 gunpowder stitched to its base. The forward part of the bag is recessed to contain the Charge Propellant Increment 2, a white cloth bag containing 311 g of propellant SC/Z008. Cartridge 2, the Charge Propelling, 155 mm, Howitzer Charge 7, L8A1 is made up from Charge 3 L4A1 and Charge Propellant Increments 4 to 7. Total weight is 7.55 kg. The Charge Propelling 155 mm, Howitzer, Charge 3, L4A1 consists of a smoke grey cloth bag containing 1.39 kg of NO25 propellant divided into two equal bundles. The charge bag is stitched into a combustible sleeve which in turn is secured in a smoke grey main charge bag. The sleeve and main charge bag are large enough to receive the propellant increments 4 to 7 which, when assembled with Charge 3, form the Charge 7 L8A1. Fitted on the base of the main charge bag is the Igniter L20A1, containing 80 g of propellant NC/200 and 18 g of G20 gunpowder. The mouth of the main charge bag is fitted with a Velcro loop and hook. The Charge Propellant Increment 4 consists of an orange cloth bag containing 529 g of NO25 propellant. The Charge Propellant Increment 5 consists of a grass green cloth bag containing 1.56 kg of N/S 134-040 propellant together with a flash inhibitor pack. This pack contains 125 g of potassium sulphate powder and is positioned in the centre of the propellant. Wrapped and secured around the front end of the propellant is 17 g of lead foil. The Charge Propellant Increment 6 consists of a dark violet cloth bag containing 2.42 kg of N/S 134-040 propellant divided into two equal bundles, each of which has lead foil strip wrapped and secured around its front end. The Charge Propellant Increment 7 consists of a beige cloth bag containing 1.49 kg of N/S 134-040 propellant divided into three equal bundles, each of which has lead foil wrapped and secured around its front end. Cartridge 3 is the Charge, Propelling, 155 mm, Howitzer, Charge 8, L10A1 . This consists of a brown combustible main case and a pink combustible end cap. The end cap contains an Igniter, Propelling, Charge L23A1 mounted on a perforated disc. The propellant charge bundle consists of 12.48 kg of NS 54.14 propellant sticks tied in five places using polyester/cotton thread and incorporating lead foil positioned under the top layer of sticks. All charges are ignited by the Primer Percussion DM 191A1 which contains a primary charge of 1.25 g of nitrocellulose S536. When fired from the 155 mm FH-70 Towed Howitzer using the three cartridge system the 155 mm Illuminating DM 106 can reach the following ranges: Charge 2 - range 3,900 to 5,900 m Charge 3 - range 4,800 to 7,500 m Charge 4 - range 6,200 to 9,500 m Charge 5 - range 8,500 to 12,500 m Charge 6 - range 11,200 to 16,800 m Charge 7 - range 14,200 to 20,900 m Charge 8 - range 17,000 to 24,700 m. When fired from the 155 mm FH-70 Towed Howitzer the 155 mm Illuminating DM 106 has a maximum muzzle velocity of 827 m/s. It is anticipated that future 155 mm propellant charge systems will involve Modular Charge Systems (MCS). Germany has already adopted the Rheinmetall DeTec Modular Propelling Charge System (MPCS) DM 72, as have Norway and Malaysia . The United Kingdom has adopted the South African SOMCHEM M90 Bi-Modular Charge System. Authorised fuzes MT L92A2 Equivalent projectiles ITALY ITALY Manufacturer Simmel Difesa SpA Type: 155 mm Illuminating DM 106A1 Description: Standard specifications Manufacturer Simmel Difesa SpA Type: 155 mm Illuminating P4 Description: Similar to 155 mm Illuminating DM 106