M67 recoilless rifle

The first recoilless rifles (RCL) were developed near the end of World War II as a lightweight form of anti-tank weaponry. They 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 man portable.

The recoilless rifle functions somewhat like a rocket launcher in that its projectile is propelled with a charge that vents at the rear of the weapon but it does not continue to burn after it has left the weapon as it does with rockets. The launcher is recoilless by venting of the gas backwards. See classical mechanics for a overview of the physics.

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 preformed to engage the rifled launch tube, spin-stabilizing the projectile, hence the term "rifle.". The "case" area of the shell is perforated to vent the propellant gases to the rear. The rocket stops burning when it leaves the tube, preventing injury to the operator.

The first recoilless rifle to enter service was the Panzerabwehrwerfer 7,5 (or PAW), a 75 mm gun developed to give German airborne troops some useful anti-tank support before the Panzerfaust 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 copied almost verbatim by the US Army, reversing the flow of technology that had occurred when the Germans copied the Bazooka. PAWs remained fairly rare during the war, but the US versions of the 75 started becoming increasingly common starting 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). 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. 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.

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