A gas operating system for a firearm includes a gas block, a barrel nut that maintains the gas block at a predetermined axial position on a barrel of the firearm, a member that is movable with respect to the gas block axially with respect to the barrel in response to pressure exerted by expanding propellant gases conveyed thereto by the gas block and a mechanical linkage receiving a force form the member urging it in an axial direction of the barrel and coupled with a loading and ejection mechanism of the firearm to convey the force thereto for operating the loading and ejection mechanism. Various embodiments of gas block assemblies and operating rods for gas operating systems for firearms are provided.