US Patent 7493845 Recoil mechanism for a gun

A recoil mechanism for a gun with a frame, a barrel and a slide, has a cylinder with a rear with external flange and an internal diaphragm spaced forwardly of the flange and between a rear chamber and a front chamber in the cylinder. A nut is fixed to the frame and an axle has a rear end threaded to the nut and extends in the cylinder. The axle has a collar trapped in the front chamber by the diaphragm. A first spring around the cylinder, has a front end abutting the slide and a rear end abutting the flange. A second spring extending at least partly in the rear chamber has a rear end abutting the nut and a front end abutting the diaphragm. A third spring in the front chamber, is shorter in length than the front chamber. A recoil adjusting plug is used with or without the recoil mechanism.