Silent/flameless ammunition special cartridges developed by the soviets in the mid 1950s by request of the KGB. NM Elizarov's team, developed a special subsonic bullet for the 7.62x39 cartridge. It was adopted for service in 1962, and given the army designation "7.62 US" (US = reduced speed Rus.). It would be resting on a piston. When fired the piston would propel to bullet forward to a speed of 170m/s. The piston would stop at the end of the Cartridge, trapping the gasses inside of it.