A muzzle booster or recoil booster is a device affixed to the muzzle of a firearm, intended to harness the energy of the escaping propellant to augment the force of recoil on portions of the firearm. Muzzle boosters are usually used to improve the reliability and/or rate of fire of a recoil operated firearm. The muzzle booster is the antithesis of the muzzle brake, which is designed to use the propellant gases to reduce the recoil of the firearm. However, unlike a muzzle brake, a muzzle booster uses the pressure of the expanding gases, rather than the reaction force, and it does not alter the felt recoil of the weapon, it merely adds more energy to the operating components.