The following information on the 9x25mm Mauser military pistol comes from Chapter 29 of Mauser Rifles and Pistols by W. H. B. Smith. Mauser Rifles and Pistols is also available to purchase in print.
In 1908 Mauser introduced this pistol to shoot a special long 9mm cartridge. Because this model was used largely for shipment to Africa, South America and the Orient, where a larger caliber than the original 7.63mm was desired, it is frequently referred to as the “Export Mauser.” Enough of them reached the United States to encourage our ammunition makers to produce the special 9mm cartridges required for this pistol; but manufacture has been discontinued for a number of years.
There is no difference in the two models except in the chamber, bore of the barrel, and sights. The description of the 7.63mm covers all features of the 9mm.
The cartridge case is straight-sided instead of bottle-necked but is the same length and head diameter as the 7.63mm. These cartridges were loaded on 10-shot clips exactly as in the case of the smaller caliber.
The bullet weighs 128 grains and may be cupro-nickel or steel jacketed. The original muzzle velocity was about 1300 to 1350 feet per second. This cartridge was never adapted to any other automatic pistol, although it was used in some European submachine guns.
This arm is a perfect example of Mauser’s system of operation. First, he designed the pistol in caliber 7.63mm to meet German requirements; next he developed a special 9mm cartridge which could be used in a pistol made on the same machinery and to the same specifications (except for bore and sights) as the smaller caliber; hence when it became necessary to convert the Mauser for German military use to shoot the totally different 9mm Luger cartridge, it was possible to do this with little more than a change of bore and a minor magazine adjustment.
All Mauser’s arms and ammunition were created on this general system, which allowed the Germans to fill foreign orders in times of peace to keep up their factory potential; and enabled them to swing into high gear for German military production on the shortest notice.