When describing the performance of a firearm cartridge, muzzle energy tends to be one of the most important measurements. Essentially, muzzle energy is the amount of force a bullet exerts at the point it has exited the barrel. That force is measured using an equation that includes the mass of the bullet and the velocity it is traveling exiting the barrel, and it is measured in foot-pounds (ft-lbs). Heavier bullets tend to have more muzzle energy than lighter ones, but the velocity of the bullet exiting the muzzle has a greater bearing on muzzle energy than its weight. Muzzle energy can be an important measurement for hunters in some states since regulators tend to factor in minimum muzzle energy for ammunition when making rules on which firearms can be used to harvest certain types of wild game.