Аround 1965, the KGB, as well as its most important rival within the Soviet intelligence system, the GRU (Intelligence Department of the General Staff, Soviet Army), both adopted the “noiseless pistol complex”, which consisted of the integrally silenced 7.62mm cartridge, known as PZ (Patron “Zmeya” – “Snake” cartridge) and the 2-barreled, derringer-type pistol known as S4.
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