recoilless rifle
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.
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.
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.