The PSS-2, as the name implies is the next generation of the PSS design which was adopted in the 1980s. The original gun boasted the ability to be shot silently without a suppressor due to its special piston based 7.62x42 SP4 ammo.
In order for the PSS to achieve this it needed to use heavy cylindrical bullets to increase the mass to stay subsonic and avoid a supersonic crack. This resulted in the bullets preforming poorly against armor this is where the PSS-2 steps in. It put a wedge shaped tip on its bullets to maintain mass while reducing the surface area that’d touch the vest on initial impact to increase penetration.
7.62x43 SP-16 ammo for the PSS-2
The PSS-2 is a recoil-operated weapon that utilizes an open breech system and is mechanically similar to its predecessor, the PSS. Its unique design includes a mechanism that slows the slide’s movement in its final stages to prevent clanging noise.
https://special-ops.org/pss-2-the-successor-to-the-famous-pss-silent-pistol/
Wow TIL Johnathan Ferguson mentioned a derringer design in the last Q&A to a question I asked. I’m guessing it was one of those two. Definitely worth their own post.
I love the piston concept too such a change in functionality by simply adding one moving part.