What is "recoilless rifle"

n. A lightweight portable weapon capable of firing artillery-type shells, used normally as anti-tank weapon.

A recoilless rifle (RCLR) or recoilless gun is a type of lightweight tube artillery that is designed to allow some of the propellant gases to escape out the rear of the weapon at the moment of ignition, creating forward thrust that counteracts some of the weapon's recoil. This allows for the elimination of much of the heavy and bulky recoiling mechanisms of a conventional cannon while still enabling the unit to fire a powerful projectile. Besides this, the lower pressures involved allow thinner walled and lighter tubes, further lowering the weight of the cannon. Technically, only devices that use a rifled barrel are recoilless rifles, while smoothbore variants are recoilless guns. This distinction is often lost, and both are often called recoilless rifles.

Though it is similar in form and appearance to a rocket launcher, it fires modified artillery shells, not rockets. The key difference from rocket launchers (whether man-portable or not) is that the projectile of the recoilless rifle has no propulsion of its own: once out of the rifle, it behaves as a normal artillery shell and does not accelerate further, as a missile or rocket would. Nevertheless, there are also boost-after-launch rocket-propelled projectiles available for modern recoilless rifles.

Because some projectile velocity is inevitably lost to the recoil compensation backblast, recoilless rifles tend to fire a fairly heavy explosive shell with less range than traditional cannons, although with a far greater ease of transport, making them popular with paratroop, mountain warfare and special forces units, where portability is of particular concern, as well as with some light infantry and infantry fire support units. Although the greatly diminished recoil allows many smaller and newer versions to be shoulder-fired by individual infantrymen, the majority of recoilless rifles in service are mounted on light tripods and intended to be carried by a small 2- or 3-man crew. The largest versions, such as the British 120 mm L4 MoBAT and L6 Wombat, retain enough bulk and recoil to be restricted to a firm vehicular mount, such as on a jeep, truck, or armored personnel carrier.