The 9ÃÂ23mm Steyr, also known as 9mm Steyr, is a centerfire pistol cartridge originally developed for the Steyr M1912 pistol.
Adopted in 1912, the 9mm Steyr was the service ammunition for most branches of the military in Austria-Hungary during World War I and remained the service ammunition for Austria, Romania and Chile between the World Wars. Some MP 34 submachine guns were also issued in this caliber in addition to 9ÃÂ25mm Mauser. When the Austrian Army was incorporated in the Wehrmacht in 1938 following the Anschluss, many Steyr M1912 pistols and MP 34 submachine guns were rebarrelled to 9ÃÂ19mm Parabellum for standardization purposes.
The cartridge headspaces on the mouth of the case. Its performance is close to that of the .38 ACP. Unrelated to the modern 9ÃÂ23mm Winchester, it is similar to the 9ÃÂ23mm Largo cartridge in performance, but their dimensions are just different enough to make them non-interchangeable.
For handloading, reloadable Boxer-primed cartridge cases can be made from 5.56ÃÂ45mm NATO brass. This requires inside neck-reaming, as such a conversion would otherwise leave unacceptably thick mid-to-rear case walls from the original cartridges to form the mouths of the new, shortened cases. At least one commercial source apparently can produce such a forming die set, complete with reamer. Loading data would be much like .38 ACP.