Adjustable gas valve for firearm

An adjustable gas valve for use in a firearm gas block having a cylinder and piston in the gas block, the valve comprising:

• a valve body configured to associate with the cylinder and having an exhaust port, the valve body including a plurality of inlet orifices rotatably alignable to selectively receive gas pressure flow from a barrel port;
• a regulator that adjustably occludes between none and all of the exhaust port;
• an internal diffuser stem configured to extend at least partially inside the valve body and having an open end directed toward the piston;
• a plurality of radial exhaust outlets leading to an annular chamber positioned adjacent the exhaust port;
• and
• an exhaust passageway operably connecting the open end with the radial exhaust outlets.