 This energy is then transferred to the base of the bullet and to the rear of the cartridge or breech, propelling the firearm "rearward" into the shooter while the projectile is propelled "forward" down the barrel, with increasing velocity, to the muzzle.The rearward energy of the firearm is the free recoil and the forward energy of the bullet is the muzzle energy.The concept of free recoil comes from the "tolerability" of gross recoil energy.