M16 modified with pushrod operating system and conversion method

A push rod operating system for a rifle comprising:

• a rifle having a barrel coupled to an upper receiver, a bolt carrier carried by the upper receiver, and a mechanical key coupled to the bolt carrier;
• a gas block coupled to the barrel, the gas block having a bore therethough;
• a rod tube extending from the gas block in communication with the bore, toward the upper receiver;
• a gas plug closing the bore of the gas block opposite the rod tube, the gas plug defining a gas chamber therein;
• an aperture formed in the barrel for venting discharge gasses, and a pathway for discharge gasses to enter the gas chamber defined by the gas plug;
• a piston rod element carried in the rod tube proximate the gas block, the piston rod element having a piston portion reciprocally received within the bore of the gas block and movable between a first position abutting the gas plug to define an operating volume, and a second position;
• and
• a push rod element carried by the rod tube and engaging the mechanical key and the piston rod element.