Recoilless

Recoilless describes a class of firearms and launch systems designed to minimize the recoil transmitted to the weapon and its operator when firing. The concept relies on momentum conservation by redirecting propellant gases rearward, expelling a counter-mass, or a combination of both, so that the forward impulse on the projectile is offset by backward impulse external to the weapon.

Most common implementations are recoilless rifles and launchers that vent propellant gases to the rear through a breech or muzzle. Some designs use a counter-mass that is expelled in the opposite direction to carry away momentum. Gas venting is typically directed through a blast opening or jacket around the barrel, reducing recoil felt by the operator but producing a strong backblast and muzzle blast. This backblast imposes safety constraints on firing positions and surrounding personnel.

Historically, recoilless weapons were developed in the early 20th century and gained widespread use in the mid- to late 20th century for anti-tank roles, light artillery support, and armored-vehicle armaments. Notable examples include a range of recoilless rifles with calibers from small to large and several anti-tank systems that relied on rearward gas venting. In many modern forces, guided missiles and other recoil-reducing technologies have largely supplanted fixed-gun recoilless systems for anti-armor roles, but recoilless designs remain in limited use where the weight savings and simple launch concepts are advantageous.

In summary, recoilless refers to mechanisms that reduce operator impulse by redirecting or countering recoil forces, at the cost of backblast and design constraints.