I recently acquired this Chinese mystery pistol from gunbroker, and unlike Ian Mccallum, I actually intend to shoot this gun. However, it is my opinion that even the slightly weaker 7.63x25mm Mauser cartridge it's still far too powerful for a straight blowback action. And while I could make my own downloaded 7.63x25mm Mauser ammo, that's tedious. And as I already intend to replace the barrel as the barrel is made from steel of unknown quality and is likely very poorly, rifled i would like to convert it to a smaller cartridge that is commercially available off the shelf. so if anybody knows any ammunition, that is small and weak enough to be safely used in a blowback action it has a case head diameter that will fit a 7.63x25mm Mauser bolt face i would greatly appreciate it if you would provide any information you can. I am also willing to replace the spring with a stronger one, if need be.