The 9×23mm Largo (9mm Largo, 9mm Bergmann–Bayard, 9mm Bayard Long) centerfire pistol cartridge was developed in 1901 for the Bergmann Mars pistol. Description and history The round was considered powerful for the day, producing a muzzle energy of between depending on the loading. A number of small changes to the Mars and the cartridge were made and the pistol that resulted was called the "Bergmann–Bayard 1903". This pistol was adopted by the Spanish army in 1905 as the "Pistola Bergmann de 9 mm. modelo 1903". Unable to find a German manufacturer to complete the Spanish order for 3,000 pistols, Theodor Bergmann turned to a Belgian manufacturer, Anciens Etablissements Pieper (who used the trademark "Bayard"), to complete the order. The final pistol, modified by AEP, was known as the "Bergmann Bayard 1908", or in Spain as the "Pistola Bergmann de 9 mm. modelo 1908". Although adopted in 1908 first deliveries did not take place until two years later. Meanwhile, other manufacturers such as Campo-Giro had adopted the 9mm Bergmann–Bayard round and, due to its long history of use in Spanish submachine guns, carbines and pistols, today it is most commonly known as the "9mm Largo". At the same time the Bergmann–Bayard model 1910 semi-automatic pistol was adopted by the Danish military and remained in production until 1935. The cartridge headspaces on the mouth of the case. With jacketed projectiles, the muzzle energy is 336 foot pounds, slightly lower than a standard-pressure 9×19mm Luger. Compared to the 9×19mm Luger +P, performance is also lower but at lower pressure in the 9×23mm Largo. While external dimensions are almost identical, the 9×23mm Largo is a very different cartridge from the modern, high-performance 9×23mm Winchester. Firing the thicker-walled 9×23mm Winchester round in a 9×23mm Largo pistol is dangerous, as old 9mm Largo pistols cannot handle the pressure generated by the 9×23mm Winchester. Performance is similar to the contemporary 9×23mm Steyr, but the cartridges were developed independently and their dimensions are just different enough to render them non-interchangeable. Firearms chambered for 9mm Largo Anciens Establissements Pieper (AEP) Bergmann Mars (1901) Pistola Bergmann–Bayard de 9mm modelo 1903 Pistola Bergmann–Bayard de 9mm modelo 1908 Bergmann–Bayard M1910 Bergmann–Bayard M1910/21 Berthodl Geipel’s Erfurter Maschinenfabrik VMP(Vollmer) EMP/MPE Erma submachine gun, Spanish made copy called m41/44. Astra-Unceta y Cia SA Esperanza y Unceta Campo-Giro Modelo 1912, 1913, 1913–16 Esperanza y Unceta Astra 400 (Modelo 1921), 1921–1926 Unceta y Compania Astra 400 (Modelo