The M20 recoilless rifle was a U.S. 75 mm calibre recoilless rifle used during the last months of the Second World War and extensively during the Korean War. It could be fired from the shoulder, from a M1917A1 .30 calibre machine gun tripod, or from a vehicle mount, typically a Jeep. Its shaped charge warhead, also known as the HEAT, was capable of penetrating 100 mm of armour. This weapon could stop the Russian made T-34 tank at ranges up to 400 yards. It was used primarily as a close infantry support weapon to engage all types of targets including infantry and armoured vehicles. The M20 proved useful against pillboxes and other types of heavy fortifications.

During World War II the U.S. military recognized that a powerful lightweight weapon was needed for defending infantry and light armour units due to advancements in armour technology by enemy forces. The Ordnance Department Small Arms Division commenced development of the a recoilless rifle and by 1944 models of a 75 mm recoilless rifle were being tested. Production of the M20 was underway by March 1945; only limited numbers were used by Allied troops on the European and Pacific theatres.

The M20 relied on a perforated artillery shell casing, combined with a rear vented breech using propellant gases from the firing of a shell, to greatly reduce the recoil of the weapon. It is this use of vented propellant gases that eliminated the need for a recoil system, thereby reducing the weight of the artillery piece and enhancing its use as a light infantry weapon.

Recoilless rifles, such as the M20, were used successfully in large numbers during the Korean War, but were phased out for the wired guided missiles introduced during the Vietnam War in the 1960's and 1970's.

Again, very popular with the VC forces because of its combined firepower and light weight. A direct copy of the obsolete US M20. It was quite adequate for the needs of the VC.