Originally designed by the Union Metallic Cartridge Company (UMC) as a black powder cartridge using nine grains of black powder, the round has been loaded with smokeless powder exclusively since 1940. It is low-powered and perfect for use in small frame concealable revolvers and derringers. The round remained popular in the United States and Europe long after the firearms chambered for it were out of production. At one time, it was considered to be the bare minimum for a self-defense round and was judged unsuitable for police work.