Even so, recoil calculated in this manner is only the starting point in a comparison with the .357 Magnum cartridge, since the latter is used in a revolver, in which the recoil energy is due to the bullet and propellant less ejecta escaping through the cylinder gap, while the .357 SIG cartridge is used in a semi-automatic pistol with recoil operation; here, a significant portion of the recoil energy is diverted to cycle the action, effectively prolonging the recoil-phase pulse.