The 5mm Bergmann is an unusual centerfire cartridge produced for very early self-loading pocket pistols. The case is steeply conical and headspaces on the conical case walls. Early versions (sometimes called the 5 mm Bergmann Rimless) were made without any rim or extraction groove; and relied upon blow-back for expulsion of the fired case from the chamber. Later Bergmann pistols provided an extractor requiring a groove which produced a semi-rimmed case. The long bullet was inadequately stabilized and tended to tumble in flight.^[1]