A recoilless rifle or recoilless gun is a lightweight weapon

Weapon

A weapon, arm, or armament is a tool or instrument used with the aim of causing damage or harm to living beings or artificial structures or systems...

 that fires a heavier projectile than would be practical to fire from a recoiling weapon of comparable size. Technically, only devices that use a rifled

Rifling

Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis...

 barrel are recoilless rifles. Smoothbore

Smoothbore

A smoothbore weapon is one which has a barrel without rifling. Smoothbores range from handheld firearms to powerful tank guns and large artillery mortars.-History of firearms and rifling:...

 variants are recoilless guns. This distinction is often lost, and both are often called recoilless rifles.

Normally used for anti-tank roles, the first effective system of this kind was developed during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 by William Kroeger and Clarence Musser.

Recoilless rifles are capable of firing artillery

Artillery

Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...

-type shells at a range and velocity

Velocity

In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...

 comparable to that of a normal light cannon

Cannon

A cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees,...

, although they are typically used to fire larger shells at lower velocities and ranges. The near complete lack of recoil

Recoil

Recoil is the backward momentum of a gun when it is discharged. In technical terms, the recoil caused by the gun exactly balances the forward momentum of the projectile and exhaust gasses, according to Newton's third law...

 allows some versions to be shoulder-fired, but the majority are mounted on light tripods and are intended to be easily carried by a soldier. A few, such as the British 120mm L4 MoBAT and L6 Wombat

L6 Wombat

The L6 Wombat, was a 120 mm calibre recoilless anti-tank rifle used by the British Army. They were used until anti-tank guided missiles such as Vigilant and MILAN took their place....

 could only practically be transported by jeep or truck, or mounted on an armoured personnel carrier.

Design

The typical recoilless gun functions very much like a conventional gun. The projectile and propellant are supplied as a single round and loaded into the breech. When fired, however, instead of all the propellant blast following the projectile out the barrel, a large portion is allowed to escape to the rear, gaining a rearward directed momentum

Momentum

In classical mechanics, linear momentum or translational momentum is the product of the mass and velocity of an object...

 which is nearly equal to the forward momentum of the projectile. This balance of momenta ensure that the momentum of the rifle/projectile/exhaust gas system is conserved without imparting much momentum (recoil) to the rifle itself. Since recoil has been mostly removed, the heavy and complex gun carriage and recoil damping mechanism can be dispensed with. Despite the name, it is rare for the forces to completely balance, and real world recoilless rifles do recoil noticeably (with varying degrees of severity). Recoilless rifles are maintenance-intensive weapons, and if the breech and gas ports are old, damaged, plugged or poorly maintained, the recoil-damping effect can be reduced or lost altogether, leading to dangerously powerful recoil. Conversely, if a projectile becomes lodged in the barrel for any reason, the entire weapon will recoil forward, in the manner of a rocket.

Unlike a rocket launcher

Shoulder-launched missile weapon

A shoulder-fired missile, shoulder-launched missile or man-portable missile is a projectile fired at a target, small enough to be carried by a single person, and fired while held on one's shoulder...

, which fires fin-stabilized rockets from a smooth bore, recoilless rifle rounds resemble conventional artillery shells. They generally have a pre-engraved rifling band

Driving band

The driving band or rotating band is part of an artillery shell, a band of soft metal near the middle of the shell, typically made of gilding metal, copper or lead...

 to engage the rifled launch tube, spin-stabilizing the projectile, hence the term "rifle". The "case" area of the shell can be perforated to vent the propellant gases which are then directed to the rear, as the base of the shell disintegrates.

Since venting hot gases to the rear can be dangerous in confined spaces, some recoilless guns such as the Armbrust

Armbrust

Armbrust is a lightweight unguided anti-tank weapon designed and developed by Messerschmitt-Bölkow-Blohm of Germany, who later sold its manufacturing rights to Chartered Industries of Singapore ....

 and MATADOR

MATADOR (weapon)

MATADOR is a man-portable, disposable anti-armor weapon system developed in a collaboration between Singapore and Israel. It is an updated version of the German Armbrust design, and operates on the same principles...

 use a combination of a countershot, smoothbore barrel and pistons to avoid both recoil and back blast. The fin stabilized Armbrust "cartridge" contains the propellant charge between two pistons with the warhead in front of one, facing forward, and an equal countermass of shredded plastic in front of the other piston. Upon firing, the propellant expands rapidly pushing the pistons outward. This pushes the projectile forwards towards the target and the countermass backwards providing the recoilless effect. The shredded plastic countermass is quickly slowed by air resistance and is harmless at a distance more than a few feet from the breech. The pistons jam at the ends of the barrel trapping the hot propellant gases inside. All this allows safe firing in enclosed spaces.

History

The first recoilless gun was developed by Commander Cleland Davis of the US Navy

United States Navy

The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

, just prior to the First World War

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

. His design, named the Davis gun

Davis gun

The Davis gun was the first true recoilless gun developed and taken into service. It was developed by Commander Cleland Davis of the US Navy, in 1910, just prior to World War I. His design connected two guns back to back, with the backwards-facing gun loaded with lead balls and grease of the same...

, connected two guns back to back, with the backwards-facing gun loaded with lead balls and grease of the same weight as the shell in the other gun. His idea was used experimentally by the British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 as an anti-Zeppelin

Zeppelin

A Zeppelin is a type of rigid airship pioneered by the German Count Ferdinand von Zeppelin in the early 20th century. It was based on designs he had outlined in 1874 and detailed in 1893. His plans were reviewed by committee in 1894 and patented in the United States on 14 March 1899...

 and anti-submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

 weapon mounted on an Handley Page O/100 bomber

Bomber

A bomber is a military aircraft designed to attack ground and sea targets, by dropping bombs on them, or – in recent years – by launching cruise missiles at them.-Classifications of bombers:...

 and intended to be installed on other aircraft.

In the Soviet Union development of recoilless weapons ("Dinamo-Reaktivnaya Pushka" (DRP), roughly "dynamic reaction cannon") began in 1923. In the 1930s many different types of weapons were built and tested with configurations ranging from 37 mm to 305 mm. Some of the smaller examples were tested in aircraft (Grigorovich I-Z

Grigorovich I-Z

-References:...

 and Tupolev I-12

Tupolev I-12

-External links:**...

) and saw some limited production and service, but development was abandoned around 1938, possibly as a side effect of the Great Purge

Great Purge

The Great Purge was a series of campaigns of political repression and persecution in the Soviet Union orchestrated by Joseph Stalin from 1936 to 1938...

. The best-known of these early recoilless rifles was the Model 1935 76 mm DRP designed by Leonid Kurchevsky

Leonid Kurchevsky

Leonid Vasilyevich Kurchevsky was a Russian/Soviet weapons designer....

. A small number of these mounted on trucks saw combat in the Winter War

Winter War

The Winter War was a military conflict between the Soviet Union and Finland. It began with a Soviet offensive on 30 November 1939 – three months after the start of World War II and the Soviet invasion of Poland – and ended on 13 March 1940 with the Moscow Peace Treaty...

. Two were captured by the Finns and tested; one example was given to the Germans in 1940.

The first recoilless rifle to enter service in Germany was the 7.5 cm Leichtgeschütz 40

7.5 cm Leichtgeschütz 40

The 7.5 cm Leichtgeschütz 40 was a recoilless gun used by the German Army during World War II.-Background:Development of recoilless weapons by Rheinmetall began in 1937 in an effort to provide airborne troops with heavy support weapons that could be dropped by parachute. Both Krupp and...

("light gun" '40), a simple 75 mm smoothbore recoilless gun developed to give German airborne troops

Airborne forces

Airborne forces are military units, usually light infantry, set up to be moved by aircraft and 'dropped' into battle. Thus they can be placed behind enemy lines, and have an ability to deploy almost anywhere with little warning...

 some useful artillery and anti-tank support that could be parachuted into battle. The 75 was found to be so useful during the invasion of Crete

Crete

Crete is the largest and most populous of the Greek islands, the fifth largest island in the Mediterranean Sea, and one of the thirteen administrative regions of Greece. It forms a significant part of the economy and cultural heritage of Greece while retaining its own local cultural traits...

 that a larger 105 mm version

10.5 cm Leichtgeschütz 42

The 10.5cm Leichtgeschütz 42, commonly the LG 42, was a German recoilless gun manufactured by Rheinmetall and used during World War II.-History:...

 was developed on the same basic pattern. Interestingly both of these weapons were loosely copied by the US Army

United States Army

The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

, reversing the flow of technology that had occurred when the Germans copied the Bazooka

Bazooka

Bazooka is the common name for a man-portable recoilless rocket antitank weapon, widely fielded by the U.S. Army. Also referred to as the "Stovepipe", the innovative bazooka was amongst the first-generation of rocket propelled anti-tank weapons used in infantry combat...

, as their own 88 mm calibre Panzerschreck

Panzerschreck

Panzerschreck was the popular name for the Raketenpanzerbüchse , an 88 mm calibre reusable anti-tank rocket launcher developed by Nazi Germany in World War II. Another popular nickname was Ofenrohr ....

 infantry anti-tank rocket system. The US did have a development program and it is not clear to what extent the design was copied, as there were in fact differences. The Japanese had also developed a portable recoilless anti-tank rifle which they had reserved for the defense of anticipated invasion of the mainland. As it was, however, these weapons remained fairly rare during the war though the US versions of the 75 started becoming increasingly common in 1945.

During the Second World War the Swedish

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 company Bofors Carl Gustaf developed a small 20 mm device, the 20mm m/42; the British expressed their interest in it, but by that point anti-tank rifle

Anti-tank rifle

An anti-tank rifle is a rifle designed to penetrate the armour of vehicles, particularly tanks. The usefulness of rifles for this purpose ran from the introduction of tanks in World War I and until the Korean War...

s were already out of date.

In 1947, the US 75 mm

M20 recoilless rifle

The M20 recoilless rifle was a U.S. 75 mm caliber recoilless rifle used during the last months of the Second World War and extensively during the Korean War. It could be fired from an M1917A1 .30 caliber machine gun tripod, or from a vehicle mount, typically a Jeep. Its shaped charge warhead,...

 was acquired as war surplus by the French military and mounted on a Vespa scooter. It was used by French paratroops as a mobile anti-tank and anti-fortification platform and saw service in Algeria and Indochina.

By the time of the Korean War

Korean War

The Korean War was a conventional war between South Korea, supported by the United Nations, and North Korea, supported by the People's Republic of China , with military material aid from the Soviet Union...

, recoilless rifles were found throughout the US forces. The "original" US recoilless rifles were the 57mm

M18 recoilless rifle

The M18 recoilless rifle was a 57 mm shoulder fired anti-tank recoilless rifle used by the U.S. Army in World War II and the Korean War. Recoilless rifles are capable of firing artillery-type shells at reduced velocities comparable to those of standard cannon, but with greater accuracy than...

 and 75mm

M20 recoilless rifle

The M20 recoilless rifle was a U.S. 75 mm caliber recoilless rifle used during the last months of the Second World War and extensively during the Korean War. It could be fired from an M1917A1 .30 caliber machine gun tripod, or from a vehicle mount, typically a Jeep. Its shaped charge warhead,...

, followed by a 105 mm (the unsuccessful M27). Newer models replacing these were the 90 mm M67

M67 recoilless rifle

The M67 recoilless rifle was a 90-mm antitank recoilless rifle made in the United States and later in the Republic of Korea. It could also be employed in an antipersonnel role with the use of the M590 antipersonnel round...

 and 106 mm M40

M40 recoilless rifle

The M40 recoilless rifle was a lightweight, portable, crew-served 105 mm weapon intended primarily as an anti-tank weapon made in the United States...

 (which was actually 105 mm caliber

Caliber

In guns including firearms, caliber or calibre is the approximate internal diameter of the barrel in relation to the diameter of the projectile used in it....

 but designated otherwise to prevent confusion of ammunition with the earlier model). The Soviets likewise adopted recoilless technology in the 1950s, most commonly in calibers 73 mm , 82 mm , and 107 mm .

The British, whose efforts were led by Denis Burney

Charles Dennistoun Burney

Sir Charles Dennistoun Burney, 2nd Baronet was an English aeronautical engineer, private inventor and Conservative Party politician....

, inventor of the Wallbuster HESH round, also developed recoilless designs. Burney demonstrated the technique with a recoilless 4-gauge shotgun

Shotgun

A shotgun is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called shot, or a solid projectile called a slug...

. His "Burney Gun" was developed to fire the Wallbuster shell against the Atlantic Wall

Atlantic Wall

The Atlantic Wall was an extensive system of coastal fortifications built by Nazi Germany between 1942 and 1944 along the western coast of Europe as a defense against an anticipated Allied invasion of the mainland continent from Great Britain.-History:On March 23, 1942 Führer Directive Number 40...

 defences, but was not required in the D-Day landings of 1944. He went on to produce many designs including a man-portable 3.45" (88 mm) recoilless rifle, the Ordnance, RCL, 3.45 in

Ordnance, RCL, 3.45 in

The 3.45 inch RCL was a British recoilless weapon, designed by Sir Dennis Burney during the Second World War. Delayed by problems due to wear upon firing, it did not see action, as was hoped, in the Far East...

, pushed into experimental service in late 1945.

Two Burney guns were designed primarily as anti-tank weapons. One was 3.45 inches in calibre and could be fired off a man's shoulder or from a light tripod. The other was 3.7 inches in calibre, and was carried on a light two-wheeled mounting. The "Ordnance RCL. 3.45in MK 1" weighed 75 lb (34 kg), was 68.5in (1.74m) long, and fired an 11 lb (5 kg) wallbuster shell to 1,000 yards. No penetration figures were ever made public. but it is fairly certain that it could knock a 10 lb slab off the back of 6 in (150 mm ) of armour plate at any range it could hit. The 3.7 was a larger weapon weighing 222 lb (100 kg); it was 112 in (2.84 m) long and fired a 22.2 lb (10 kg) wallbuster to 2,000 yards; it is estimated that this could have dealt successfully with armour up to 10 in (254 mm) thick. Post-war work developed and deployed the BAT series of recoilless rifles, culminating in the 120 mm L6 Wombat

L6 Wombat

The L6 Wombat, was a 120 mm calibre recoilless anti-tank rifle used by the British Army. They were used until anti-tank guided missiles such as Vigilant and MILAN took their place....

 ("Weapon of Magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

, Battalion

Battalion

A battalion is a military unit of around 300–1,200 soldiers usually consisting of between two and seven companies and typically commanded by either a Lieutenant Colonel or a Colonel...

 Anti-tank"). This was too large to be transported by infantry, and was usually towed by jeep. The weapon was aimed via a spotting rifle, which fired .50 BMG

.50 BMG

The .50 Browning Machine Gun or 12.7×99mm NATO is a cartridge developed for the Browning .50 caliber machine gun in the late 1910s. Entering service officially in 1921, the round is based on a greatly scaled-up .30-06 cartridge...

 rounds whose trajectory matched that of the main weapon. Tracer rounds were fired first until hits were observed before firing off the main gun.

Lightweight SPG-9

SPG-9

The SPG-9 Kopye is a Russian tripod-mounted man-portable, 73 millimetre calibre recoilless gun developed by the Soviet Union. It fires fin-stabilised, rocket-assisted HE and HEAT projectiles similar to those fired by the 73 mm 2A28 Grom low pressure gun of the BMP-1 vehicle...

 73 mm and B10

B-10 recoilless rifle

The B-10 recoilless rifle is a Soviet 82 mm smoothbore recoilless rifle. It could be carried on the rear of a BTR-50 armoured personnel carrier. It was a development of the earlier SPG-82, and entered Soviet service during 1954...

 82 mm heavy recoilless rifles are still in service in the Russian army in airborne units, and are found quite commonly around the world in the inventories of former Soviet client states, where they are usually used as antitank guns.

During the 1960s and 1970s, wire-guided missiles began to supplant recoilless rifles in the anti-tank role. The recoilless rifle started to disappear from the military except in areas such as the Arctic where battery-powered Dragons and wire-guided TOWs would fail due to extreme low temperatures. The former 6th Light Infantry Division in Alaska used the M67 in its special weapons platoons. The last major use was the M50 Ontos, which mounted six of the US 106 mm on a light (9 ton) tracked chassis first developed for use by the US Army airborne troops in 1950. However the Army considered them useless, and the Marines adopted the vehicle in a limited role. They used them to great effect as an anti-personnel fire support vehicle during the Vietnam War

Vietnam War

The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...

. The crews continued to report that the Ontos was a very effective fighting vehicle in this role, but the military brass continued to argue for heavier designs, and in 1970 the Ontos was removed from service and most were broken up. However the recoilless rifle found other roles, most notably in the India-Pakistan confrontation in Kashmir, where it was used against bunkers and as artillery in otherwise inhospitable terrain.

The Viet Minh

Viet Minh

Việt Minh was a national independence coalition formed at Pac Bo on May 19, 1941. The Việt Minh initially formed to seek independence for Vietnam from the French Empire. When the Japanese occupation began, the Việt Minh opposed Japan with support from the United States and the Republic of China...

 also developed their own recoilless rifle under the direction of Tran Dai Nghia. The Vietnamese version was named SKZ or Sung khong giat (a Vietnamese translation of "recoilless rifle") and was used intensively in assaulting the French bunkers and fortified positions. The larger version of SKZ was DKZ or Phao khong giat ("recoilless artillery").

Today one of several remaining front-line recoilless rifles in the armies of industrialized nations is the famous Carl Gustav recoilless rifle

Carl Gustav recoilless rifle

The Carl Gustav is the common name for the 84 mm man-portable reusable multi-role recoilless rifle produced by Saab Bofors Dynamics in Sweden...

, an 84 mm man-portable anti-tank weapon. First introduced in 1946, it is still in widespread use throughout the world today, and has even been re-introduced into the US Marine Corps as an anti-bunker weapon. The US

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

-made, M40

M40 recoilless rifle

The M40 recoilless rifle was a lightweight, portable, crew-served 105 mm weapon intended primarily as an anti-tank weapon made in the United States...

 106 mm recoilless rifles, usually mounted on jeeps or similar small vehicles, are very common in the armies of many poorer countries, where they serve in the role of tank destroyer

Tank destroyer

A tank destroyer is a type of armored fighting vehicle armed with a gun or missile launcher, and is designed specifically to engage enemy armored vehicles...

s. The 84 mm (Carl Gustav recoilless rifle) can be used, along with 66 mm (AKA M72 LAW

M72 LAW

The M72 LAW is a portable one-shot 66 mm unguided anti-tank weapon, designed in the United States by Paul V. Choate, Charles B. Weeks, and Frank A. Spinale et al...

) and LAW 80

LAW 80

The LAW 80 , sometimes erroneously referred to as LAW 94, is a man-portable, disposable anti-tank weapon currently in use by the British Army and a few other militaries.-Description:...

 for mouse-holing

Mouse-holing

Mouse-holing is a tactic used in urban warfare, in which soldiers create access to adjoining rooms or buildings by blasting or tunneling through a wall. This tactic is used to avoid open streets where advancing infantry, caught in enfilade, are easily targeted by machine-gun and sniper...

 whilst fighting in built-up areas (FIBUA). This is where impromptu "doors" are added to a building to gain entry, hopefully avoiding the prepared defences of the occupiers. Many nations also use a weapon related to the Carl Gustav, the one-shot AT-4

AT4

The AT4 is an 84-mm unguided, portable, single-shot recoilless smoothbore weapon built in Sweden by Saab Bofors Dynamics...

 recoilless weapon.

Deployed by the United States in the 1960s, the M-388 Davy Crockett

Davy Crockett (nuclear device)

The M-28 or M-29 Davy Crockett Weapon System was a tactical nuclear recoilless gun for firing the M388 nuclear projectile that was deployed by the United States during the Cold War...

 used a recoilless rifle to launch a tactical nuclear warhead.

Older 75 mm rifles are still used by the U.S. National Park Service

National Park Service

The National Park Service is the U.S. federal agency that manages all national parks, many national monuments, and other conservation and historical properties with various title designations...

 as a system for avalanche control

Avalanche control

Avalanche control or avalanche defense activities reduce the hazard avalanches pose to human life, activity, and property. Avalanche control begins with a risk assessment conducted by surveying for potential avalanche terrain by identifying geographic features such as vegetation patterns,...

, and Washington State Department of Transportation

Washington State Department of Transportation

The Washington State Department of Transportation , was established in 1905. The agency, led by a Secretary and overseen by the Governor, is a Washington governmental agency that constructs, maintains, and regulates the use of the state's transportation infrastructure...

 uses a 105 mm recoilless rifle for avalanche control on Interstate 90

Interstate 90

Interstate 90 is the longest Interstate Highway in the United States at . It is the northernmost coast-to-coast interstate, and parallels US 20 for the most part. Its western terminus is in Seattle, at Edgar Martinez Drive S. near Safeco Field and CenturyLink Field, and its eastern terminus is in...

.