Steyr AUG HBAR The Steyr AUG HBAR is a longer , heavier - barreled version for use as a light machine gun variant of the Steyr AUG . Description . The AUG HBAR is a gas - operated weapon system developed by Steyr - Mannlicher GmbH of Austria from the base modular AUG assault rifle family line . The AUG family was a revolutionary , if somewhat futuristic - looking , bullpup weapons design of the late 1970s that featured base components across an assault rifle , carbine and light machine gun type , differing mainly in length of the barrel for the appropriate role . The AUG HBAR is categorized as a " light - support machine gun " and can be used by infantry squads to suppress enemy positions or support offensive - minded infantry actions . Beyond its lengthened heavy - duty barrel , the major difference between the AUG assault rifle and the AUG HBAR is its automatic firing action from an open bolt . Externally , the AUG - LMG follows closely with the clean lines of the original AUG weapon family and maintains its fully ambidextrous offerings , making it equally useful for left - or right - handed shooters . Such operation is made possible by replacing the bolt per operator discretion . The design is dominated by the large stock holding the action , magazine and feed aft of the trigger group . The trigger is encircled by a hand guard that connects the pistol grip to the underside of the receiver . Spent shell casings are ejected through a port located along the upper portion of the rear stock . Like other AUG weapons , the AUG HBAR features a built - in optical sight , integrated along the top of the receiver , and offers 1 . 5x viewing . The scope housing also doubles as the weapon ' s carrying handle for portability . A foldable vertical foregrip is situated ahead of the trigger group . The long featureless barrel extends away from the receiver and is fitted with a special muzzle brake / compensator intended to retard the weapon ' s recoil action to an extent . Under the barrel , close to the muzzle , is a collapsible bipod . The weapon maintains a running length of 900mm with the barrel being 621mm with six - grooves and a right - hand twist . Rate - of - fire is limited to roughly 750 rounds per minute with a muzzle velocity of 3 , 198 feet per second . Empty weight is a manageable 4 . 03 kilograms . The AUG - LMG fires the standard NATO 5 . 56x45mm rimless cartridge from a 30 - or 42 - round box magazine . Magazines are curved in the traditional nature for improved ergonomics when handling in the heat of combat and are made slightly transparent so the operator can instantly visually recognize the remaining ammunition count . Use of box magazines also restricts the effective rate - of - fire for the AUG HBAR when compared to her belt - fed contemporaries but continuous fire is improved - some 300 rounds can be fired without overheating issues for the barrel . The AUG HBAR exists in one other production form as the AUG HBAR - T . Essentially identical to the AUG HBAR system , the AUG HBAR - T does away with the integrated optics sight in the carrying handle and , instead , makes use of an accessories rail for thermal imaging , optical or electro - optical sight devices . The standard scope is a 4x Schmidt & Bender telescopic sight .