The GSh-18 (ГШ-18) made by KBP Instrument Design Bureau of Tula Russia.
It is 9x19mm and can fire 7N21 (7H21) and 7N31 (7H31) +P+ high pressure, armor piercing rounds, capable of piercing 8mm of steel at a distance of 15 to 20 meters. It has a 18 round magazine.
Its safety is built into the trigger and it only taken off if a finger is on the trigger.
