.41 Special

The .41 Special—also commonly known as .41 Spl (pronounced "forty-one special"), .41 Spc, or 10.4x29mmR (metric designation)—is a wildcat (non-standardized) cartridge designed for revolvers, made to be a less powerful variant of the established .41 Remington Magnum. The cartridge was intended for police work, security and personal defense, using a 200 grain bullet at 900 feet per second. While proposed as early as 1955, it remains a niche, custom cartridge.

History
In 1932, Colt researched a proposed ".41 Special" cartridge, but that shared only a name with the modern wildcat, having different measurements and even different bore diameter (.385). The concept of a .41 Special was later brought up by gunwriter Elmer Keith in his 1955 work Sixguns, where he proposed the .41 special as an analog to the .44 Special cartridge, but the idea did not gain ground.

Keith and Bill Jordan later proposed the .41 Magnum cartridge, which was formally adopted by Remington Arms in 1964. Thus counter to common practice, a "magnum" offering was standardized before a weaker "special" variant was ever introduced.

In the late 1980s pistolsmith Hamilton Bowen revived the idea of a 200gr bullet at 900fps in his custom designs.

Firearms
While large-scale production firearms have not been produced for this niche chambering, custom gunsmiths have adapted existing firearms to use it, generally by machining a new cylinder and expanding the bore of existing .357 Magnum revolvers. Ammunition is not commercially produced, but boutique runs of brass for handloading, with proper .41 Special headstamps, have been issued.

Among the first gunsmiths to make a purpose-built firearm for this chambering was Hamilton Bowen, who modified the .357 caliber Ruger Security-Six and GP100 revolvers to accommodate the .41 Special, as well as a Colt revolver and a S&W 586.