Other meanings of M20 recoilless rifle
Artillery
The M20 recoilless rifle is a 75 mm, lightweight, air-cooled, breech-loaded recoilless rifle developed by the United States during World War II and used extensively in the Korean War. It was designed to give infantry a portable anti-tank and general-purpose fire support weapon, firing a 75 mm shell through a vented breech to counter recoil. The M20 was the first American recoilless rifle to see combat, and it remained in service with U.S. forces until the late 1950s, when it was superseded by the 106 mm M40.
The M20 was developed in response to a 1943 U.S. Army requirement for a lightweight anti-tank weapon capable of defeating German armor. The design, led by engineers at the Frankford Arsenal, used a rifled barrel with a vented breech that expelled propellant gases rearward, canceling recoil. This allowed the weapon to be mounted on a lightweight tripod or even fired from the shoulder in emergencies, though the latter was discouraged due to the blast. The M20 fired a fixed round with a shaped-charge high-explosive anti-tank (HEAT) projectile, which could penetrate up to 100 mm of armor at 500 yards. The weapon was adopted in 1944 and saw limited service in the European theater, where it proved effective against bunkers and fortified positions.
The M20 saw its most extensive use during the Korean War, where it was issued to infantry and airborne units as a primary anti-tank and direct-fire support weapon. It was particularly valued for its portability—at 114 pounds, it could be broken down into two loads for transport—and its ability to destroy North Korean T-34 tanks, which had earlier proved resistant to bazooka fire. The M20 was also used in the Vietnam War in limited numbers by South Vietnamese forces and U.S. advisors. However, its effectiveness was hampered by a relatively slow muzzle velocity and a distinctive backblast that revealed the firing position, making crews vulnerable to counter-battery fire.
The M20 was produced in several variants, including the M20B1, which featured a simplified breech mechanism, and the M20A1, which had a modified mount. The primary ammunition types included the M344 HEAT round, the M346 high-explosive (HE) round, and the M347 smoke round. A practice round, the M348, was also developed for training. The HEAT round was effective against armor, but the HE round was more commonly used against personnel and fortifications. The M20's ammunition was shared with the British 75 mm recoilless rifle, the L40, which was used by Commonwealth forces, though the two weapons were not fully interoperable.1
One lesser-known fact is that the M20 was used by the U.S. Marine Corps in the Pacific theater in 1945, where it was employed against Japanese pillboxes on Okinawa. Another is that the weapon was exported to over 20 countries, including France, which used it in Indochina and Algeria, and Israel, which used it in the 1956 Suez Crisis. The M20 also influenced the design of later recoilless rifles, such as the Soviet B-10 and the Swedish Carl Gustaf. A curious detail: the M20's backblast could be lethal within a 30-meter danger zone, and crews were trained to fire only from positions with clear rear areas. The weapon was also mounted on vehicles, including the M38 Jeep, in a limited number of configurations.2
The M20 was a pioneering recoilless rifle that bridged the gap between anti-tank rifles and heavier artillery, and its design principles persist in modern weapons.
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