The 9mm Winchester Magnum, which is also known as the 9×29mm, is a centerfire handgun cartridge developed by Winchester in the late 1970s. The cartridge was developed to duplicate the performance of the .357 S&W Magnum in an auto-pistol cartridge.^[2]

The first handgun which chambered the cartridge was the Wildey pistol. Since then, Thompson/Center and LAR Grizzly Win Mag have produced barrels chambered for this cartridge and AMT chambered their Automag III^[3] for it too, but the cartridge never reached the popularity enjoyed by other handgun cartridges.^{[citation needed]}

Starline Brass in Sedalia, Missouri, still make brass for this cartridge, although much of its production is now used to make 9mm blank firing cartridges for firearms chambered for 9×19mm, as this is easier to accomplish than using .223 Remington (5.56×45mm) cases, which may leave the neck area of the blank too thick to crimp properly. 9mm Winchester Magnum cases can also be trimmed and resized for reloading 9×25mm Mauser.