Firearm with gas operating system

A semi-automatic or automatic rifle having an indirect gas operating system, comprising:

• a gas block fluid coupled to a bore of a barrel of the rifle;
• a bolt carrier slidably received within a receiver of the rifle;
• a sleeve removably secured to a forward end of the gas block of the rifle;
• a piston slidably received within the gas block, wherein the gas block and the sleeve fluidly couple the piston to the bore of the rifle;
• wherein an increase in pressure in the bore of the rifle causes the piston to move away from the sleeve;
• wherein the sleeve and the piston are each capable of being removed from the rifle through the forward end of the gas block;
• and
• wherein the receiver has an integral hand guard portion and a removable hand guard portion and wherein the removable hand guard portion when removed from the receiver provides access to a barrel nut that secures the barrel to the receiver.