9×23mm Largo

The 9×23mm Largo, better known by its military name 9mm Bergmann–Bayard, is a rimless, tapered-case pistol cartridge Theodor Bergmann and Hugo Schmeisser designed in 1903 for Bergmann’s own self-loading pistols. It found its lasting home not in Germany but in Spain, which adopted it in 1905 for the Campo-Giro and later the Astra 400 service pistols, and in Denmark, which chambered it in the Bergmann–Bayard M1910/21. Spanish service use continued into the 1980s, giving the round an unusually long working life for an early-twentieth-century military pistol cartridge.

Its 9.0 mm bullet diameter and 23.1 mm case put it dimensionally between the 9×19mm Parabellum that eclipsed it and the longer 9×23mm Winchester and Steyr rounds that share its case length by coincidence rather than lineage — the three 9×23mm-class cartridges are not interchangeable, and this entry describes the Spanish/Danish military round specifically, not the unrelated American or Austrian ones of the same nominal length.

This entry carries dimensions from the cited Wikipedia infobox, recorded as estimated because no free dimensional standard exists for this cartridge from any standards body — it was never adopted commercially outside Spanish and Danish military service. One ball load’s bullet mass is recorded, also estimated; no source states a test barrel length for any published velocity figure, so none is recorded and the cartridge computes no muzzle energy or trajectory. No maximum pressure figure is published free for it either.