Firearm having a direct gas impingement operating system

A method of removably securing a gas regulating sleeve and a gas line of a gas operating system to an automatic or semi-automatic rifle, comprising:

• fluidly coupling a gas block to a bore of a barrel of the rifle;
• removably locating and securing the gas regulating sleeve in the gas block, the gas regulating sleeve being in fluid communication with the bore of the barrel, a gas line fixed to the sleeve, the gas line being in fluid communication with the bore via the gas regulating sleeve and the gas block, and wherein a portion of the gas line is received within an impingement cylinder of a bolt assembly of the rifle when the bolt assembly is in a first position, and wherein the impingement cylinder moves away from the gas line as it moves from the first position to a second position due to gases passing through the gas line from the gas block and wherein the gas regulating sleeve remains stationary with respect to the gas block as the impingement cylinder moves between the first position and the second position;
• and
• wherein the gas regulating sleeve and the gas line are removable from the gas block without disconnecting the barrel from the receiver and without removal of the gas block from the barrel.