Recoilless rifle

M67 recoilless rifle.

Recoilless Rifle mechanism and method of operation.

A recoilless rifle (RCL) is a lightweight form of anti-tank weaponry. The first effective system of this kind was developed during World War II.

Recoilless rifles are capable of firing artillery-type shells at a range and velocity comparable to that of a normal light cannon, although they are typically used to fire larger shells at lower velocities and ranges. The near complete lack of recoil allows some versions to be shoulder-fired, but the majority are mounted on light tripods, and are easily carried by a man.

The recoilless rifle 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 driving the projectile forward a large portion is directed in the opposite direction. Since recoil has been mostly removed, much of the weighty and complex gun carriage and recoil damping mechanism can be dispensed with. It is rare for the momentum to completely balance and real world recoilless rifles do recoil noticeably.

Unlike a rocket launcher, which fires fin-stabilized rockets from a smooth bore, recoilless rifle rounds resemble conventional artillery shells. They generally have a rifling band 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, or the base of the shell disintegrates.

History

First proved by an American, Commander Davis, during the . His design had two guns connected back to back, the rear facing gun being loaded with lead balls and grease to an equal weight as the shell in the other gun. His idea was used experimentally by the British as an anti-Zeppelin and anti-submarine weapon mounted on an O/100 bomber aircraft. During the Second World War the Swedish company Carl Gustav developed a small 20 mm device, the 20 mm m/42; the British expressed their interest in it, but by that point anti-tank rifles were already out of date.

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 calibers ranging from 37 mm to 305 mm. Some of the smaller examples were tested in aircraft and through some limited production and service, but development was abandoned around 1938, possibly as a side effect of Great Purge. The best-known of these early recoilless rifles was the Model 1935 76 mm DRP designed by L.V. Kurchevski. A small number of these mounted on trucks saw combat in the Winter War. 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 ("light gun" '40), a 75 mm gun developed to give German airborne troops some useful anti-tank support before the Panzerfaust, itself a simple unrifled recoilless gun, became widespread. The 75 was found to be so useful during the invasion of Crete that a larger 105 mm version was developed on the same basic pattern. Interestingly both of these weapons were loosely copied by the US Army, reversing the flow of technology that had occurred when the Germans copied the Bazooka. 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, PAWs remained fairly rare during the war though the US versions of the 75 started becoming increasingly common in 1945.

By the time of the Korean War recoilless rifles were found throughout the US forces. The original 75 mm and 106 mm versions had also been joined by new 57 mm and 90 mm versions. The "original" US recoilless rifles were the 57 mm and 75 mm followed by a 105 mm. The new models replacing these were the 90 mm and 106 mm. The Soviets likewise enthusiastically adopted recoilless rifle (actually recoilless "guns" as they were smoothbore) technology in the 1950s, most commonly in calibers 73 mm, 82 mm, and 110 mm (107 mm, not 110 mm).

The British, whose efforts were led by Denis Burney, inventor of the Wallbuster HESH round, were developing recoilless designs. Burney demonstrated the technique with a recoilless 4 bore shotgun. His "Burney Gun" was developed to fire the Wallbuster shell against the Atlantic Wall defences but was not required. He went on to produce many designs including a man-portable 3.45" (88 mm) recoilless rifle, the Ordnance, RCL, 3.45 in pushed into experimental service in late 1945. Post-war work developed and deployed the BAT series of recoilless rifles culminating in the 120 mm L6 Wombat (Weapon of Magnesium, Battalion Anti-tank).

Lightweight 73 mm recoilless rifles are still in service in the Russian army in airborne units, and Soviet B10 82 mm heavy recoilless rifles are found quite commonly around the world in the inventories of former Soviet client states, where it is usually used as an antitank gun.

As the wire-guided missile became more and more popular in the late 1960s and early 1970s, the recoilless rifle started to disappear from the military. The last major use was the Ontos tank, 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 picked them up instead, albeit only 176 of them. They used them to great effect as a fire support vehicle during the Vietnam War. The crews continued to report 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.

Today the only remaining front-line recoilless rifle in the armies of most industrialized Western nations is the famous Carl Gustav rifle, an 84 mm man-portable anti-tank weapon. Similar in conception and use to the Bazooka, the weapon differs primarily in using rifling for stabilization rather than fins, and does not include the complex breech that is the mark of most RCL designs. 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. M40 recoilless rifle 106 mm recoilless rifles of US manufacture, 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 destroyers.

Perhaps the oddest adaptation of a recoilless rocket was the M-388 Davy Crockett, which used a recoilless rifle to launch a tactical nuclear warhead, deployed by the United States in the 1960's.

Older discarded 75 mm weapons are still used by the U.S. National Park Service as a system for avalanche control, an interesting case of swords to ploughshares.