Smith & Wesson J-Frame revolvers have had your back since 1950. These small revolvers were designed to fire a full power round and are as simple and easy to use as they are reliable. Available in various calibers and with three diverse hammer designs, it is no surprise that the Smith & Wesson J-Frame has become the most popular, small-frame, defense revolver on the market. In 1995, Smith & Wesson introduced the Model 640, the first J frame revolver chambered in the powerful .357 Magnum round. Based on Model 40 Centennial, the Model 640 is a small frame concealed hammer revolver that packs a full-sized punch. The Model 640 Pro Series integrates the time-tested features of the original with modern advancements and competition specifications and features.