With that barrel, the round would probably pack about the same heat as a Russian ппщ (pay pay sha) submachine gun which uses a similar 7.62x25 cartridge.
The two cartridges are almost the same, dimensionally. People may quibble about them being interchangable, but I would not worry about it in guns of good condition. Much harder to find .30 Mauser ammo than it is 7.62x25.
It was the most powerful common pistol round in existence until the .357 Magnum showed up, as I recall. It was highly regarded in its time. The PPsH submachinegun of the Soviets in WWII (The Great Patriot War) did significant execution.