Ft-Lb ≡ Joules?!

Air rifle power (specifically muzzle energy) is typically measured in either Joules or Ft-Lb. I never understood how these could be equivalent. The crux of the confusion comes from the fact that a pound can describe both a weight and a force. Really it should be called 'foot pound-force' or 'ft-lbf'. From Wikipedia : Pound-force should not be confused with pound-mass (lb), often simply called…