The PPS-43 is a lightweirght fully automatic-only blow-back submachine gun that is effective to approximately 200 metres. The addition of a folding metallic butt stock allows the PPS-43 to further reduce it's size for transport or when carried by a soldier. the PPS-43 started as an answer to the problems that were posed by the PPSh-41, specifically the size and weight of the weapon. The PPS-43 also had a reduced rate of fire, as compared to the PPSh-41, which made managing it easier. The PPS-43 was designed and started it's production in Leningrad during the siege, with the limited materials and machines avaible in the city.
PPS-1943 on Wikipedia