|9mm Bergmann–Bayard, 9mm Largo|
|Place of origin||German Empire|
|Case type||Rimless, tapered|
|Bullet diameter||9.02 mm (0.355 in)|
|Neck diameter||9.63 mm (0.379 in)|
|Base diameter||9.91 mm (0.390 in)|
|Rim diameter||9.96 mm (0.392 in)|
|Case length||23.11 mm (0.910 in)|
|Overall length||33.53 mm (1.320 in)|
|Primer type||Small pistol|
|Test barrel length: 150 mm (5.9 in)|
The 9×23mm Largo (9mm Largo, 9mm Bergmann–Bayard, 9mm Bayard Long) centerfire pistol cartridge was developed in 1901 for the Bergmann Mars pistol. The round was considered powerful for the day, producing a muzzle energy of between 330 and 430 ft·lbf (450 and 580 J) depending on the loading. A number of small changes to the Mars and the cartridge were made and the pistol that eventuated 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 3000 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.
The cartridge headspaces on the mouth of the case. With 125 gr (8.1 g; 0.29 oz) 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
- Bergmann Mars (1901)
- Pistola Bergmann–Bayard de 9mm modelo 1903
- Pistola Bergmann–Bayard de 9mm modelo 1908
- Bergmann–Bayard M1910
- Bergmann–Bayard M1910/21
- 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 1921), 1926–1945 or 1946
- Astra Model F (selective fire 'broomhandle' type pistol) 1934–1935
- Astra A-80
- Astra Custom SPS (IPSC racegun) 1996–?
- Arrizabalaga Sharp-Shooter
- Arrizabalaga JO.LO.AR., 1924–?
- A.D.S.A. Model 1953 submachine gun 1953–?
Destroyer carbine and similar 9mm Largo Carbines
- Ayra Durex et al.
- Jose Luis Maquibar
- Onena Carbine
- Ignacio Zubillaga
Fábrica de Armas, A Coruña
- Modelo 1941/44 submachine gun (copy of the Vollmer Erma in 9mm Largo) 1941–mid fifties
- Copy of the Bergmann MP28 in 9mm Largo
- "No maker" Astra 400 (Modelo 1921), 1938–1940's
- M 1938 Labora submachine gun
- Gabilondo Llama Modelo IV
- Gabilondo Llama Modelo V
- Gabilondo Llama Modelo VII
- Gabilondo Llama Modelo VIII
- Gabilondo Llama Modelo Extra
- Model 3R submachine gun 1959–?
- "Naranjero" submachine gun (Modified Bergmann MP28)
- RE (Republica Española) made Astra 400 (Modelo 1921), 1936–1939
- F. Ascaso made Astra 400 (Modelo 1921), 1936–1939
- Bonifacio Echeverria Star Modelo Militar 1920, 1920–1921
- Bonifacio Echeverria Star Modelo Militar 1921, 1921 only
- Bonifacio Echeverria Star Modelo Militar 1922, 1922–1931
- Bonifacio Echeverria Star Modelo A (early w/flat backstrap), 1924–1931
- Bonifacio Echeverria Star Modelo A (late w/1911 Colt-style backstrap),1931–1983
- Bonifacio Echeverria Star Modelo M (slightly larger than A), 1931–1983
- Bonifacio Echeverria Star Modelo MD (M w/selective fire), 1931–1983
- Bonifacio Echeverria Star Modelo Super-A (A w/quick takedown), 1946–1983
- Bonifacio Echeverria Star Modelo Super-M (M w/quick takedown), 1946–1983
- Bonifacio Echeverria Star Modelo AS (A w/magazine safety, quick takedown, loaded chamber indicator), 1956–1983
- Bonifacio Echeverria Star Modelo MS (M w/quick takedown, loaded chamber indicator), 1956–1983
- Star Model Z-45 Submachine gun
- Model Z-62 submachine gun
- Wilson, R. K. Textbook of Automatic Pistols, p.233. Plantersville, SC: Small Arms Technical Publishing Company, 1943.