Russia’s Federal Protective Service (FSO) have announced that they will adopt the MP-443 “Yarygin” pistol chambered in the unusual 9x21mm Gyurza cartridge. This is the first time I have heard of a MP-443 chambered in 9x21mm. The 9x21mm Gyurza (not to be confused with the IWI / IMI / Israeli 9x21mm) has previously only been used with the Vector SR-1 pistol and SR-2 Veresk submachine gun.

Wikipedia has this to say about the 9x21mm …