Steyr AUG
The Steyr AUG is an Austrian bullpup assault rifle chambered for the 5.56×45mm NATO intermediate cartridge, designed in the 1960s by Steyr-Daimler-Puch, and now manufactured by Steyr Arms GmbH & Co KG.
The AUG was adopted by the Austrian Army in 1977 as the StG 77, where it replaced the 7.62×51mm NATO StG 58 automatic rifle. In production since 1977, it is the standard small arm of the Bundesheer and various Austrian federal police units and its variants have also been adopted by the armed forces of dozens of countries, with some using it as a standard-issue service rifle.
The importation of the Steyr AUG into the United States began in the 1980s as the AUG/SA. The AUG was banned from importation in 1989 under President George H. W. Bush's executive order restricting the import of foreign-made semiautomatic rifles deemed not to have "a legitimate sporting use." Six years into the ban, AUG buyers gained a reprieve as cosmetic changes to the carbine's design allowed importation once again. Changes included redesigning its pistol grip into a thumbhole stock and leaving its barrel unthreaded to prevent attachment of a flash hider or suppressor.
The Federal Assault Weapons Ban, passed in 1994, further prohibited the manufacture of additional Steyr AUGs or their copies. The ban expired in 2004, and in 2008, Steyr Arms worked with Sabre Defence to produce parts legally in the U.S.
Design details
The Steyr AUG is a selective-fire, bullpup assault rifle with a conventional gas-piston-operated action that fires from a closed bolt. It is designed as a Modular Weapon System that could be quickly configured as an assault rifle, a carbine, a submachine gun and even an open-bolt light machine gun.The AUG is chambered for the 5.56×45mm NATO cartridge and has the standard 1:9 rifling twist that will stabilise both SS109/M855 and M193 rounds. Some nations, including Australia, Ireland and New Zealand, use a version with a 1:7 twist optimised for the SS109 NATO round. The submachine gun variants are chambered in either 9×19mm Parabellum or.40 S&W. In Enforce Tac 2025, a Steyr AUG chambered in 7.62×39mm was unveiled.
The AUG consists of six interchangeable assemblies: the barrel, receiver with integrated telescopic sight or Picatinny rail, bolt carrier assembly, trigger mechanism, stock and magazine. The AUG employs a very high level of advanced firearms technology and is made with the extensive use of polymers and aluminium components.
The AUG comes with a muzzle cap, spare bolt for left-handed shooters, blank-firing adaptor, cleaning kit, sling and either an American M7 or German KCB-77 M1 bayonet.
Engineering
The quick-change barrel used in the AUG is cold hammer-forged for increased precision and durability; its bore, chamber and certain components of the gas system are chrome-plated. The standard rifle-length barrel features 6 right-hand grooves and a rifling twist rate of 228 mm. An external sleeve is shrunk onto the barrel and carries the gas port and cylinder, gas valve and forward grip hinge jaw. There is a short cylinder which contains a piston and its associated return spring. The barrel locks into a steel insert inside the receiver through a system of eight lugs arranged around the chamber end, and is equipped with a folding vertical grip that helps to pivot and withdraw the barrel during barrel changes. The most compact of the barrels has a fixed vertical grip.The receiver housing is a steel-reinforced aluminium extrusion finished with a baked enamel coating. It holds the steel bearings for the barrel lugs and the guide rods. The non-reciprocating plastic cocking handle works in a slot on the left side of the receiver and is connected to the bolt carrier's left guide rod. The cocking handle has a forward assist feature—alternatively called a "silent cocking device"—allowing the user to fully push the bolt home without racking the charging handle. A bolt hold-open device locks the bolt carrier back after the last round has been fired. The AUG A3s feature a bolt release button; prior to this development, all AUGs and the USR required the user to rack the charging handle to disengage the bolt hold-open after inserting a fresh magazine. Older versions of the AUG can be upgraded to use the newer A3 stock and hammer pack.
The AUG's stock is made from fibreglass-reinforced polyamide 66. At the forward end is the pistol grip with an enlarged forward trigger guard completely enclosing the firing hand that allows the rifle to be operated with winter gloves. The trigger is hung permanently on the pistol grip, together with its two operating rods, which run in guides past the magazine housing. Behind that is the locking catch for the stock group. Pressing this to the right will separate the receiver and stock. The magazine catch is behind the housing, on the underside of the stock. Above the housing are the two ejector openings, one of which is always covered by a removable strip of plastic. The rear of the stock forms the actual shoulder rest, which contains the hammer unit and the end of the bolt path. The butt is closed by an endplate which is held in place by the rear sling swivel. This swivel is attached to a pin which pushes in across the butt and secures the plate. There is a cavity under the buttplate that holds a cleaning kit.
Operating mechanism
The AUG has a rotating bolt that features 7 radial locking lugs and is unlocked through a pin on the bolt body and a recessed camming guide machined into the bolt carrier. The bolt carrier itself is guided by two guide rods brazed to it and these rods run inside steel bearings in the receiver. The guide rods are hollow and contain the return springs. The bolt also contains a claw extractor that forms the eighth locking lug and a spring-loaded "bump"-type casing ejector.The gas cylinder is offset to the right side of the barrel and works with one of the two guide rods. The AUG uses a short-stroke piston system where the right guide rod serves as the action rod, transmitting the rearward motion of the gas-driven piston to the bolt carrier. The left-hand rod provides retracting handle pressure when connected by the forward assist and can also be utilised as a reamer to remove fouling in the gas cylinder. The firearm uses a 3-position gas valve. The first setting, marked with a small dot, is used for normal operation. The second setting, illustrated with a large dot, indicates fouled conditions. The third, "GR" closed position is used to launch rifle grenades.
The AUG is hammer-fired and the firing mechanism is contained in the rear of the stock, near the butt, covered by a synthetic rubber shoulder plate. The hammer group is made entirely of plastics except for the springs and pins and is contained in an open-topped plastic box which lies between the magazine and the buttplate. During firing the recoiling bolt group travels over the top of it, resetting the hammer. Since the trigger is located some distance away, it transmits its energy through a sear lever which passes by the side of the magazine. The firing pin is operated by a polymer hammer under pressure from a coil spring.
Some common criticisms of the AUG's trigger are the trigger feeling "mushy" and having excessive take-up. This is due to the relatively imprecise nature of how the trigger linkage is installed by the factory. The trigger can be "tuned" by the user in roughly 15 to 60 minutes with a 12 inch-pound wrench with a hex bit.