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Cartridge, 57 mm: HE M306 and M306A1
Region
Brazil
China
Italy
Category
Ammunition, Missiles and precision weapons
The 57 mm HE M306 and M306A1 are both fixed rounds with the forged steel projectile crimped rigidly to the perforated steel cartridge case. The thin-walled projectile has a short ogive and is encircled towards the flat base by a single pre-engraved gilding metal drive band. The 57 mm HE M306 projectile is filled with 250 g of TNT; the M306A1 has 250 g of Composition B. The nose-mounted fuze is either a PD M503, M503A1 or M503A2, all of which function either on impact or graze. Early examples used the PD M89 fuze.
The cartridge case involved may either be an M30A1B1 or M30A1B2. Both are made of steel and have 400 circular perforations in the sidewalls. The solid base has a central M46 , M60 or M60A1 percussion primer. Approximately 454 g of M10 propellant is loosely loaded into a plastic liner inside the cartridge case. Maximum range of the HE M306/M306A1 is 4,508 m and muzzle velocity 366 m/s. The training round equivalent of the 57 mm HE M306/M306A1 is the Cartridge, 57 mm: TP M306A1. This is virtually identical to the HE rounds but the projectile contains only a small black powder marking charge weighing 31 g, plus 183 g of an inert material. On impact the marker charge produces flash and smoke for spotting purposes. The first US recoilless rifle was the 57 mm T15 which first appeared, along with its (then) novel ammunition, in late 1943. The T15 was standardised as the M18 while the later M18A1 had its chamber and breech block handle in a different position. Although the M18 and M18A1 have been out of service with the US armed forces for many years and 57 mm RCL ammunition is no longer produced in the USA, the M18 and M18A1 continue to provide good service elsewhere and 57 mm RCL ammunition is still produced by a few manufacturers. At one time it was manufactured in China. A copy of the M18A1 is still produced in Brazil by Hydroar SA while a Communist Chinese copy of the M18A1 is known as the 57 mm Type 36. The 57 mm HE M306 was one of the original items of US RCL ammunition developed during the Second World War. The more common M306A1 differs in the type of filling and the design of the crimping groove. Applications include m18 and M18A1 rifles.