The invention relates to recoilless firearms, the gun carriage of which has zero recoil during a shot. The recoilless firearm comprising a gun carriage, a fire control tool, and a barrel, which contains at least a breechblock, a primer-igniter, a propellant charge and a projectile, wherein the barrel is connected to the gun carriage with the possibility of movement in the gun carriage during a shot under the impact of the propellant gas on the breechblock. The barrel is provided with a possibility of disconnecting from the gun carriage before the shot. The fire control tool is connected to the barrel and provides the barrel displacing in the gun carriage for carrying out the shot, and the breechblock is equipped with a firing mechanism, which acts on the primer-igniter when the barrel is displaced in the gun carriage. The invention provides safety of a shot via the guaranteed elimination of recoil during a shot, and also increases the efficacy of neutralizing large targets due to the applicability of high-impulse ammunition when shooting under the water, shooting from the air into the water, shooting in the air and also in weightlessness in the open space.