Ruger Mark IV pistols are the latest evolution of Ruger's original 1949 Standard Auto Pistol. Ruger Mark IV improvements include the use of a solid one-piece fully machined grip frame, a simple take-down mechanism for easy disassembly and cleaning, an improved bolt stop leaver, an ambidextrous manual safety, and a drop-free magazine release. The Ruger Mark IV 22/45 features a bull barrel, fully adjustable target sights and light weight polymer "22/45" grip frame that matches the grip angle of the popular "1911"-style pistol. The Ruger Mark IV 22/45 uses Mark IV 22/45 magazines only. Mark IV 22/45 magazines are not compatible with the Mark III 22/45. The Ruger Mark IV pistol is equipped with a magazine disconnect. This device prevents the trigger from being pulled if the magazine is removed from the pistol.