A gas operating system for automatic cycling of a pistol-caliber firearm is disclosed. The disclosed system may be configured to utilize gas produced by combustion of pistol cartridge propellant to automatically cycle the firearm. To that end, the disclosed system may include a gas block which routes high-pressure gas from the barrel through a gas port to a piston. The location of the gas port may be selected to lie within a region of the barrel which generally corresponds with the peak of the pressure curve associated with a given pistol cartridge. The high-pressure gas may impinge on the piston head, forcing the piston rearward and into physical contact with a short-stroke operating rod affixed to the bolt carrier of the host firearm. Consequently, the bolt carrier may be driven rearward, allowing for cycling of the firearm to progress.