Cartridge, 57 mm: HEAT M307 and M307A1

liner provides a passage from the fuze to a tetryl booster pellet in the base of the projectile. Thus, as the fuze functions on impact it ignites a small shaped charge, creating a flash jet which passes through the steel sleeve to light the booster pellet and detonate the shaped charge explosive from the rear, thereby improving its efficiency. The high-velocity metal particle jet produced by the warhead can penetrate up to 76 mm of armour plate. The cartridge case involved may be the M30A1 or M30A1B1, both are made of steel and have 400 perforations in their sidewalls. The solid base has a central M60 or M60A1 percussion primer. There is approximately 454 g of M10 propellant loosely loaded into a plastic liner inside the cartridge case; the M307 used a paper liner. Maximum range of the 57 mm HEAT M307/M307A1 is 3,930 m and muzzle velocity 366 m/s. The 57 mm HEAT M307 was one of the original items of American 57 mm recoilless rifle ammunition developed during the Second World War. It was originally developed for use against armoured targets but its deployment extended to bunkers and similar hard targets. The 57 mm HEAT M307A1 differs from the M307 as it uses a plastic liner to hold the propelling charge inside the cartridge case instead of a paper liner, together with a later model of percussion primer. The 57 mm HEAT M307 is rarely, if ever, encountered today. Applications include m18 and M18A1 rifles.