M20 Recoilless Rifle: While Not Effective Against Tanks, It Obliterated Enemy Pillboxes

Photo Credit: Cassowary Colorizations / NARA / Wikimedia Commons CC BY 2.0
Photo Credit: Cassowary Colorizations / NARA / Wikimedia Commons CC BY 2.0

The M20 recoilless rifle saw limited service at the end of World War II and was used extensively in Korea. It was only capable of penetrating armor of up to 100 mm thick, making it ineffective against tanks like the Soviet T-34. However, it was effective as an infantry support weapon against lightly-armored vehicles and enemy pillboxes.

Development of a new recoilless rifle

Three Ethiopian soldiers preparing to fire an M20 Recoilless Rifle
Ethiopian soldiers with an M20 Recoilless Rifle in Korea, 1951. (Photo Credit: Unknown Author / Defense Imagery / Wikimedia Commons / Public Domain)

In the midst of the Second World War, the US Army decided troops needed a lightweight weapon that could be used by advancing infantrymen, but was still powerful enough against enemy armor. In 1944, the Small Arms Division of the Ordnance Department began developing a recoilless rifle that would eventually become the M20.

The United States had already developed smaller recoilless rifles, such as the M18, with a 75 mm version having begun testing. Once the trials were successfully completed, the M20 entered production in March 1945.

M20 Recoilless Rifle specs

US Marine standing with Sergeant Reckless, who's equipped with an M20 Recoilless Rifle
US Marine Corps horse Sergeant Reckless equipped with an M20 Recoilless Rifle, 1952-55. (Photo Credit: Andrew Geer / US Marine Corps / Wikimedia Commons / Public Domain)

The M20 Recoilless Rifle weighed between 103 and 114.5 pounds, with a length of nearly seven feet. Despite these specifications, it was designed as a portable weapon for infantry units. The overall concept was simple. The rifled barrel had the outward appearance of a tube, and, toward the rear, it tapered outward to an enlarged exhaust section.

The M20 used perforated artillery shell casings, which worked in conjunction with the exhaust part to allow propellant gasses to escape. This eliminated the recoil system, which, in turn, reduced the rifle’s weight, making it more effective for infantry use.

Using a conventional breech-loading system, the M20 could fire a range of 75 mm rounds: High-Explosive Anti-Tank (HEAT), High-Explosive (HE), High-Explosive Plastic/Plasticized (HEP) and White Phosphorous (WP). It had a muzzle velocity of 1,000 feet per second, allowing for a maximum firing range of 3.9 miles.

The M20 could be operated by a single soldier, if necessary, but was almost always manned by two – a gunner and a loader – who would move the rifle using carrying handles on either side of the barrel. Unlike smaller recoilless rifles, it wouldn’t be held by the operator when in use, with the M1917A1 tripod being utilized. Both could be fixed to a Jeep, allowing for greater mobility.

Korean War

Two American soldiers loading an M20 Recoilless Rifle, while another crouches to the side with their own weapon
American soldiers with an M20 Recoilless Rifle in Korea. (Photo Credit: US Department of Defense / National Archives at College Park – Still Pictures / Wikimedia Commons / Public Domain)

The M20 Recoilless Rifle saw limited service during the final months of World War II, in both the European and Pacific Theaters. That being said, it, along with the Bazooka, were the two main American anti-tank weapons in Korea.

Almost immediately, the weapon showed its shortcomings. During the Battle of Osan, the M20 failed to destroy any T-34 tanks operated by the North Koreans. Following the deployment of the M20 Super Bazooka, the rifle was no longer used as an anti-tank weapon and, instead, served as infantry support. It flourished in this role, destroying enemy trenches, pillboxes and bunkers.

Between Korea and the Vietnam War, the M20 was phased out of service, with the US military developing wire-guided missile systems. With the introduction of the BGM-71 TOW in 1970, the rifle was fully retired from service with the US. Until the 1990s, the country still had a large stockpile of M20 ammunition, and, in an effort to use it up, the weapons were deployed by the US National Park Service (NPS) and National Forest Service to start controlled avalanches.

Several countries equipped the M20 Recoilless Rifle

Three Dutch soldiers kneeling beside an M20 Recoilless Rifle
Dutch soldiers with an M20 Recoilless Rifle, 1954. (Photo Credit: Anefo / Dutch National Archives / Wikimedia Commons CC0 1.0)

The first non-American combat use of the M20 Recoilless Rifle was by the French during the First Indochina War. In addition to France, other NATO and American allies purchased the weapon, including the Netherlands, South Korea, Argentina, Colombia, the Philippines, South Vietnam and Saudi Arabia. The most recent deployment of the M20 was by the Royal Moroccan Army during the Western Sahara War, between 1975-91.

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China produced unlicensed copies of the M20, known as the Type 52 and 56. The Type 52 was an exact copy, while the 56 allowed for the rifle to fire fin-stabilized HEAT rounds. The former was equipped by 10 nations, while the latter was used by six. These copies were used, most notably, by the North Vietnamese Army (NVA) and Viet Cong during the Vietnam War.

Ryan McLachlan

Ryan McLachlan is a historian and content writer for Hive Media. He received his Bachelor of Arts in History and Classical Studies and his Master of Arts in History from the University of Western Ontario. Ryan’s research focused on military history, and he is particularly interested in the conflicts fought by the United Kingdom from the Napoleonic Wars to the Falklands War.

Ryan’s other historical interests include naval and maritime history, the history of aviation, the British Empire, and the British Monarchy. He is also interested in the lives of Sir Winston Churchill and Admiral Lord Nelson. Ryan enjoys teaching, reading, writing, and sharing history with anyone who will listen.

In his spare time, he enjoys watching period dramas such as Murdoch Mysteries and Ripper Street and also enjoys reading classical literature and Shakespeare. He also plays football and is an afternoon tea connoisseur.