Abstract: An indirect gas operating system for an M4 type automatic or semi-automatic firearm. The indirect gas operating system has a gas block having a cylinder. The gas block is fitted to a barrel assembly having a bore with the cylinder in communication with the bore. A piston having a piston end and a striking end has the piston end fitted to the cylinder. A bolt assembly having a striking surface is provided. When a cartridge is fired, gas displaces the piston end and causes the striking end to strike the striking surface displacing the bolt assembly. The cylinder and the piston are together removable as an assembly from the firearm without removal of the gas block.

Abstract: A rifle having a receiver with an integral hand guard and a barrel. The barrel is connected to the receiver. The hand guard extends over and surrounds the barrel. A removable hand guard is attached to the receiver by an attachment that stably holds the removable hand guard to the receiver. The attachment is arranged for allowing detachment and removal of the removable hand guard from the receiver without removal of fasteners.

Abstract: An M-4 firearm having a lower receiver assembly and an upper receiver assembly. The upper receiver assembly is connected to the lower receiver assembly. The lower receiver assembly has a fire control assembly. The upper receiver assembly has a barrel and a hand guard. The hand guard has a venting features for allowing cooling air to pass therethrough. The hand guard has a heat shield mounted therein. The hand guard has at least one peripheral device mounting rail. The hand guard has an upper portion and a removable lower portion. The removable lower portion has at least one peripheral device mounting rail. The removable lower portion may be removed and replaced with a different second removable lower portion without the removal of fasteners.

Abstract: An M-4 firearm having a lower receiver assembly and an upper, receiver assembly. The upper receiver assembly is connected to the lower receiver assembly. The lower receiver assembly has a fire control assembly. The upper receiver assembly has a barrel and a hand guard. The hand guard has a venting features for allowing cooling air to pass therethrough. The hand guard has a heat shield mounted therein. The hand guard has at least one peripheral device mounting rail. The hand guard has an upper portion and a removable lower portion. The removable lower portion has at least one peripheral device mounting rail. The removable lower portion may be removed and replaced with a different second removable lower portion without the removal of fasteners.