The AUG was designed as a family of rifles that could be quickly adapted to a wide variety of roles with the change of the barrel to a desired length and profile, among which are: a compact 350 mm (13.8
light machine gun barrel. The AUG is a modular, bullpup configuration rifle that employs a high level of synthetic and advanced alloy components.
The primary variant of the rifle designated the AUG A1, consists of six main assemblies: the barrel, receiver with integrated telescopic sight, bolt and bolt carrier, trigger mechanism, stock and magazine. The AUG is a selective fire rifle with a gas piston operated action that fires from a closed bolt. The rotating bolt features 7 locking lugs and is unlocked by means of a stud on the bolt body and a recessed camming guide in the bolt carrier's surface. The bolt carrier itself is guided by two rods inside the receiver with two recoil springs directly behind it, around the two spring guides. The bolt contains both a claw extractor and a casing ejector. The firearm uses a short-stroke piston system (the right guide rod serves as the action rod, transmitting the rearward motion of the gas-driven piston to the bolt carrier), a 3-position gas valve (the first setting is used for normal operation, the second setting - fouled conditions while the third, closed position is used to launch rifle grenades), a two-stage trigger (pulling the trigger halfway produces semi-automatic fire, pulling the trigger all the way to the rear produces fully automatic fire) and a safety mechanism (cross-bolt, button type), located above the grip. In its “safe” position the trigger is mechanically disabled. Some versions have an ALO or "automatic lockout", a small projection at the base of the trigger. In the exposed position the ALO stops the trigger being squeezed past the single shot position. If needed, the ALO can be pushed up to permit automatic fire.
The rifle is fed from translucent, double-column box magazines (molded from a high-strength polymer) with a 30-round capacity and an empty weight of Template:Convert/LonAoffDbSoff
The quick-change barrels used in the AUG series are cold hammer forged for increased precision and durability, their bores and certain components of the gas system are chromium plated. The barrels all have 6 right-hand grooves and a rifling twist rate of 228 mm (9
. They lock into a steel insert inside the receiver via eight lugs and are equipped with folding, vertical grips that help to pivot the barrels out during changing. The most compact of the barrels has a fixed vertical grip. Flash hiders were used on the 350 mm (13.8
barrel configurations: the first – fitted with a fixed, post foresight (used on the standard rifle version with aperture iron sights) and the second type – equipped with a 40 mmM203grenade launcher that can be used mounted on the standard length rifle or autonomously – as a stand-alone grenade launcher after attaching a shoulder pad to the end of the 5.56 mm barrel.
The receiver housing is a steel-reinforced aluminum extrusion. The cocking handle is located at the left side and is connected with the bolt carrier's left guide rod. The cocking handle has a forward assist feature - alternativley called a "silent cocking device" - used for pushing the bolt shut without recocking the rifle. A bolt hold open device locks the bolt carrier assembly back when changing magazines. Integrated with the receiver is a fixed carry handle that contains a 1.5x telescopic sight made by Swarovski. It contains a simple ring reticle with a basic range finder that is designed so that at 300 meters (Expression error: Unexpected < operator.
tall man-size target will completely fill it giving the shooter a relatively accurate method of estimating range. The sights cannot be set to specific ranges or adjusted for windage and are usually zeroed for 300 meters. The rifle also has a back-up iron sight with a rear notch and front blade, located on top of the optical sight housing, used in case of failure or damage to the primary optical sight. In order to mount a wide range of optics and accessories, a receiver with a NATO-standard Picatinny rail and detachable carry handle was also developed.
The rifle’s stock, made from fiberglass-reinforced polyamide 66, has a pistol grip with an enlarged trigger guard that allows the gun to be fired with gloves.
The AUG uses the 5.56x45mm NATO cartridge and will stabilize both SS109/M855 and M193 bullets.
The rifle is fully ambidextrous (after swapping out the bolt and replacing ejection port covers).
A single fire version of the rifle known as the AUG P is available to the civilian and law enforcement markets. It features a shorter, 407 mm (16
barrel and a modified bolt, carrier and trigger assembly that will only allow semi-automatic fire.
The light machine gun variant can be modified to fire from an open bolt (called the AUG LMG in this configuration). To accomplish this, a modified bolt carrier, striker and trigger mechanism with sear are used.
The rifle comes standard with four magazines, a muzzle cap, spare bolt for left-handed shooters, blank-firing adaptor, cleaning kit, sling and either an AmericanM7 or Austrian KCB bayonet.
Based on the AUG, Steyr developed the 9 mm AUG submachine gun that fires the 9x19mm Parabellum pistol cartridge. It is an automatic, blowback-operated model that fires from a closed bolt. Unlike the rifle variants, this SMG has a unique 420 mm (16.5
barrel with 6 right-hand grooves at a 250 mm (1:9.8 in) rifling twist rate, ended with a recoil compensator, a slightly different charging handle and a magazine well conversion insert enabling the use of standard 25-round box magazines from the Steyr MPi 81 and TMP submachine guns. A conversion kit used to transform any rifle variant into the submachine gun is also available. It consists of a barrel, bolt, adapter insert and magazine.
Steyr AUG P Special Receiver: Railed version of the AUG P.
Steyr AUG 9 mm (AUG SMG/AUG Para): Chambered in 9x19mm Parabellum differs from A1 model in barrel, bolt, magazine and a magazine well adapter which allows the rifle to feed from Steyr MPi 69 magazines. This version operates as a blowback firearm, without use of the rifle's gas system. For some time a kit of the above components was available to convert any AUG into a 9 mm SMG.
MSAR STG-556: Introduced at the 2007 SHOT Show, the MSAR STG-556 is manufactured by Microtech Small Arms Research Inc. (a subsidiary of Microtech Knives) and is an AUG A1 clone significantly re-engineered in its working system and principle as it features a forward assist and a bolt hold-open device as seen on the M16 rifle; otherwise the MSAR STG-556 retains the original AUG features, such as feeding from proprietary translucent plastic magazines and having the quick-change barrel option. The rifle can be converted from either having a telescopic sight or a MIL-STD-1913 rail. It is available in either civilian, semi-automatic only and military/LE, select-fire variants. 
TPD USA AXR: Revealed at the 2007 SHOT Show, manufactured by Tactical Products Design Inc. as an AUG A2 clone capable of semi-automatic only fire, aimed for both the civilian and law enforcement markets, and fed by STANAG magazines; the manufacturer sells clear plastic magazines which are STANAG 4179 compliant and will readily fit in any rifle with a compatible magazine catch. 
barrel. The F88C is generally used as a personal defensive weapon where maneuverability is an issue, such as in armoured vehicles.
Austeyr F88S: A version of the Australian Austeyr F88 with an integrated Picatinny rail in place of the standard optic that allows the attachment of various sights (night vision devices, magnified and non-magnified optics such as the ELCAN C79, Trijicon ACOG or Aimpoint).
F88S-A1C: The Austeyr F88S-A1C is a compact variant of the F88 fitted with a Picatinny rail. The rifle has a 407 mm (16
barrel. Typically issued to front-line combat infantry units with room and weight constraints such as cavalry, reconnaissance, light horse, paratroopers and airfield defence guards (RAAF).
Austeyr F88 GLA: Australian Army version with an M203 grenade launcher. It features an Inter-bar (armourer attached) interface, an RM Equipment M203PI grenade launcher, and a Knight's Armament quadrant sight assembly to which a Firepoint red dot sight is attached. The bayonet lugs and forward vertical foregrip are removed.
F88T: ADI has developed a .22-caliber training rifle for use by the Australian Army. The rifle provides an economical training alternative, with very low ammunition cost, which can be used in environmentally sensitive training areas and ranges where "overshooting" is an issue, and there is less likely of a chance to injure instructors and other persons. Also used by the Australian Defence Force Cadets.
Austeyr F88A4: ADI’s proposed F88A4 will incorporate multiple Picatinny rails for the fitting of legacy systems such as the M203P140 mm
grenade launcher as well as both commercial off-the-shelf (COTS) and military off-the-shelf (MOTS) sighting and battle enhancement accessories. Also it must be noted that the A4 has only been bought in limited numbers (reportedly only 10 units) for evaluation purposes.