A firearm gas piston system provides tool-less removal and adjustment of gas flow along a nonlinear gradient and directs exhaust discharge away from the operator. The system includes a gas block with gas channels for directing exhaust gas away from an operator and a gas plug bore configured to accommodate insertion of a gas plug. The gas plug can include an actuator for rotating the gas plug, a key that fits within a key notch and key channel inside the gas plug bore to secure the gas plug within the bore, and a regulator portion to control the flow of discharge gas from a firearm barrel. The regulator portion includes a passage with two opening segments that accept discharge gas from the barrel and direct the gas through another opening disposed in a regulator cutout and to a piston portion of the gas block.