badgerben: the correct cartridge for the 30 caliber Broomhandle Mauser pistol is the .30 Mauser cartridge. The 7.62x25mm is the correct cartridge for the CZ52, although the CZ, the Tokarev and anything other than the Broomhandle will easily handle the 30 Mauser. The 30 Mauser was designed to take an 85-88 grain 308 diameter bullet at 1400'/sec. The 7.62x25mm was originally loaded for the TT-33 Tokarev pistol at about teh same velocity but later on was loaded to higher pressures for the ppsh-41/43, the Communist sub maching gun called the 'Burp' Gun.
Today, due to the higher velocities the 7.62x25 is loaded to, it is best to shoot only the 30 Mauser in that Broomhandle.
One more thing - Mentor Arms on Long Island, NY remanufactures the Broomhandle Mauser pistols. These things came in 3 calibers, the 30 Mauser, the 9mm Luger/Parabellum (9x19), and the 9mm Export, a rimless cartridge the length of the 9x23mm case with a 128 grain bullet at about 1280'/sec, I believe. If you want to shoot another cartridge or not worry about the pressure concern, your friend may wish to have his Mauser rebored. Mikey.
Hope this helps. Mikey.