Rifle

In a rifle having an upper receiver carrying a bolt carrier and a barrel attached to the upper receiver, the rifle comprising:

• an operating system including:
• a piston assembly coupled to the barrel for receiving propelling gasses from the barrel, the piston assembly including a cylinder with an open forward end, a piston moveable between a retracted position and an extended position within the cylinder, and an end plug removably closing the open forward end of the cylinder to permit passage of the piston therethrough when the plug is removed;
• at least one push rod element extending along the barrel and having a first end positioned to be engaged by the piston and a second end engaging the bolt carrier for movement of the bolt carrier from a closed position to an open position as the piston moves from the retracted position to the extended position;
• a tubular handguard having a forward end, a rearward end, a central void extending between the forward end and the rearward end, and a channel extending therealong adjacent the central void, the tubular handguard received about the barrel with the channel providing clearance for the operating system and the forward end being open to permit access to the piston assembly of the operating system;
• and
• a barrel nut coupling the barrel to the receiver, and the tubular handguard encircling the barrel is received about and coupled to the barrel nut.

A rifle comprising:

• an upper receiver/handguard assembly including an upper receiver and a handguard extending therefrom;
• a bolt carrier carried by the upper receiver;
• a barrel attached to the upper receiver and encircled by the handguard;
• an operating system extending along the barrel and terminating in a barrel coupling including a piston assembly coupled to the barrel for receiving propelling gasses from the barrel, the piston assembly having a cylinder with an open forward end, a piston/pushrod assembly moveable between a retracted position and an extended position, and an end plug removably closing the open forward end of the cylinder to permit passage of the piston/pushrod assembly therethrough when the plug is removed;
• the handguard being tubular and having a forward end, a rearward end, a central void extending between the forward end and the rearward end, and a channel extending therealong adjacent the central void, a barrel nut coupling the barrel to the upper receiver, and the tubular handguard encircling the barrel is received about and coupled to the barrel nut;
• and
• the channel of the tubular handguard providing clearance for the operating system and the forward end being open to permit access to the barrel coupling of the operating system.