The Smith & Wesson 645 and Smith & Wesson 745 are second-generation semi-automatic pistols which predates Smith & Wesson's 4500 series of handguns. The S&W 645/745 is chambered for the .45 ACP cartridge. The S&W 645 is constructed almost entirely from stainless steel and is thus extremely resistant to harsh weather conditions, whereas the S&W 745 has a stainless steel frame and a blued carbon steel slide. The S&W 645 was introduced in 1985 and discontinued in 1988. The S&W 745 was produced from 1986 to 1990, primarily as a single-action competition gun for IPSC shooting.