 Some also included a bushing type recoil compensator and a wrench for use with the compensator.The standard recoil spring used in the Mark I and II pistols chambered for the .45 Winchester Magnum has a 27lb rating, compared to the 16lb rating for a standard M1911 pistol chambered for .45 ACP.The heavy spring, combined with the greater inertia of the massive slide, results in a manageable recoil impulse without resorting to the gas operation of the Desert Eagle and Wildey designs.