The .32 Special had a unique property when it was introduced back in 1902. While the contemporary .30-30 cartridge was designed exclusively for use with smokeless powder, the .32 was a smokeless powder cartridge that, according to Winchester advertising, was designed to be reloadable with black or smokeless powder. To ease the problem of black powder fouling, the rifling twist in Winchester .32 Spec. Rifle barrels was 1 turn in 16 inches, rather than the 1-in-12 twist of the .30-30. That is what made it "Special."

The .32 Special could be said to be based on a .30-30 case necked-up to accept .321 inch diameter bullets. Actually, both the .30-30 and the .32 Special are based on a necked-down, bottleneck version of the rimmed .38-55 case. The rim diameter is .506 inch, and the shoulder angle is about 14.5 degrees. The case is 2.04 inches long, and the maximum overall cartridge length is 2.565 inches. The SAAMI maximum average pressure is 38,000 cup. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.