Muzzle energy is the measured energy in translational kinetic energy (Et) imparted to a projectile or bullet at the muzzle. Muzzle energy is also the same energy as kinetic energy (Ek), recoil energy, down range energy or impact energy. The difference between these five energies is the location of the body in motion: your recoiling firearm rearward, a bullet just exiting the muzzle, a projectile moving down range or impacting a target and kinetic energy being all the above. Muzzle energy is expressed by the Joule (J) or Foot-pound force (ft-lbf).