A gas flow control valve comprising coupling means for coupling to a measurement tube, wherein the coupling means are compatible with existing means for coupling valves to the measurement tube, means for directing gas from a well head through the gas flow control valve and out of an exit port, means for finely tuning the flow rate of gas passing through the flow control valve comprising, means for longitudinally translating a valve needle via rotation of a rotating assembly, wherein the valve needle comprises a tapered portion and a shoulder, wherein the tapered portion of the valve needle comprises a truncated cone which increases in diameter in the direction of gas flow, and means for visually indicating the longitudinal position of the gas flow control valve.