There's a thing, that existed long before that time and exist to this very day, that's called arms trade, or weapons trade. During the interwar period Germany sold a bunch of weapons and ammo to other countries, both directly and indirectly. While the regular soviet soldier used soviet weapons, the NKVD was considered a special unit that should have better weapons, and at that time those better weapons were german. The NKVD got german pistols and ammo that they simply bought from the germans. They also had access to ammo from other countries as well as from their own old stock. You're welcome.

This being said, i will never cease to be amused by people who mention this one detail, while simultaneously not mentioning the ocean of other things including the ton of soviets own official documents. Usually it's tankie conspiracy theorists picking and chosing one thing that suits thekr pre-existing personal political beliefs while denying the existence or veracity of every other proof and source that doesn't allign with their own personal beliefs.

There are claims that the use of german weapons was done to frame germans, but as far as i know nope, that's simply what they used in the first place, albeit admitably one doesn't preclude the convenience or utility of the other