The Steyr Armee Universal Gewehr (AUG) was one of the most successful bullpup designs ever manufactured. Completed in 1977, it was adopted as the standard infantry rifle by its native Austria and, eventually, by a handful of other nations. Semi-automatic versions were imported only in limited numbers before succumbing to the 1989 importation ban.

STG-556 barrels are fluted and threaded at the muzzle for a five-vent brake that is solid at the bottom. The folding foregrip is mounted to a sleeve that holds the gas tube, regulator and piston.

   Enter AUG aficionado and entrepreneur Anthony Marfione, who in 2005 founded a new company called Microtech Small Arms Research (MSAR) to manufacture a product-improved AUG clone called the STG-556. The new gun follows the original in basic layout in that it is a gas-operated bullpup whose design features include: an investment cast aluminum receiver, an M16-style rotating bolt, quick-change barrels, and a short-stroke gas piston/cylinder.
   The STG-556 also includes: an M16-style forward bolt assist button on the left-side of the stock just above the take-down latch; a manual bolt hold-open/release, also on the left side of the stock just above the magazine release; colored dots on each surface of the square crossbolt safety to indicate its status; and a host of enhancements in materials and finishes. Plans include a 6.8 Rem. SPC version and conversion kits in that chambering for existing 5.56 mm carbines.
   The hollow polymer stock houses the safety, the housing latch that retains the receiver, the magazine release and the removable fire-control unit. A long, U-shaped trigger bar actuates the double-hook sear.
   The heart of the STG-556 is its triangular cross section investment cast receiver. The barrel passes through its upper portion where multiple locking lugs engage the front of an attached steel locking collar. The rear of the collar is also the locking point for the rotating bolt head, which rides in a carrier with a pair of tubes that pass through the receivers lower portion. The left one contacts the operating handle, while the longer right one contacts the gas piston in the barrel assembly. The tubes contain the recoil springs, which act against rods permanently mounted in the buttstock.
   Removing the bolt head from the carrier for maintenance is easily accomplished without tools. The polymer operating handle on the receiver’s left is used to retract the bolt and can be locked rearward by rotating it about 30 degrees clockwise. The bolt can then be released simply by tapping the handle counterclockwise.

The STG-556 field strips easily into its basic component groups without
the use of tools.

   STG-556 barrels are fluted and threaded at the muzzle for a five-vent brake that is solid at the bottom. Microtech offers several barrel lengths, all with 5.56 mm NATO-spec chambers, including a 14" barrel with a 1:7" twist, which would require registration of the arm as a Short Barreled Rife, the tested 16” length with a 1:8" twist, and 20" and 24" lengths, both of which have 1:9" twists.
   The folding foregrip is mounted to a sleeve that holds the gas tube, regulator and piston. The regulator can be set for normal use (“ears” horizontal), for more gas when the rifle is extremely dirty, or closed off to allow single-shot operation.
   Bullpup designs, in general, dictate a long friction-prone triggerbar; so, not surprisingly, the STG-556’s trigger suffers in that regard. The company plans to offer a marksman version with a match-grade trigger.
   The safety blocks the trigger when pressed to the right. An M16-style forward assist allows silent closing of the bolt, and a combination bolt hold-open/release facilitates rapid, one-hand magazine changes. The magazine release, a large serrated, aluminum lever at the rear center of the magazine well, allows ambidextrous operation. Microtech magazines are made of translucent, high-strength polymer and will fit in original AUG rifles, but not vice versa.
   Like the original, the STG-556 can be converted to left-hand use by moving the ejection port cover to the right side and replacing the bolt with a left-hand model available from the manufacturer. Of course, the charging handle, forward assist and bolt stop/release remain on the rifle’s left side regardless of ejection port configuration.
   We shot the STG-556 with its removable AUG-style 1.5X combat optic and a variety of factory ammunition. Only one malfunction—attributable to remanufactured ball ammunition—was experienced in approximately 300 rounds fired.    Accuracy results were acceptable for such a low-magnification optic with a relatively coarse ring-and-post style reticle, and testers agreed that a higher magnification optic would have allowed tighter groups. The sight housing also incorporates emergency iron sights slightly offset to the right of bore axis.
   Despite its unorthodox appearance, the STG-556 has superb ergonomics. The rifle was a pleasure to shoot, and staffers became comfortable with it after just a few minutes’ familiarization. The buttplate’s considerable downpitch and ribbed rubber surface kept it firmly in the shoulder pocket. The vertical fore-grip made it easy to control and mitigated the wobble caused by the break of the 11-lb. trigger. With practice, we found it could be manipulated with relative precision.
   The MSAR STG-556 improves upon the original AUG design with several useful features. Compact, reliable and pleasant-shooting, it recalls a classice rifle that may always appear to be just a little ahead of its time.

MSAR STG-556

Manufacturer:
Microtech Small Arms Research
(Dept. AR), 300 Chestnut St. Ext., Bradford, PA 16701; (814) 363-9260;
www.msarinc.com

Model Caliber: 5.56 mm NATO
(.223 Rem.)

Action Type: gas-operated
semi-automatic rifle

Receiver: investment cast
7075-T6 aluminum

Barrel: phosphated, chrome-lined, 4150 chrome moly steel with quick-change capability; 14", 16" (tested), 20" or 24"

Rifling: six-groove, 1:7" (14"), 1:8" (16"), 1:9" (20" and 24") RH twist

Magazine: five-, 10-, 20-, 30- and 42-round detachable translucent polymer box

Sights: emergency irons integrated into housing of 1.5X optical sight with heavy post and circle reticle; (optional Picatinny rails with numbered slots available in 5", 9", 12" lengths

Trigger Pull: 11 lbs., 2 ozs. pull

Stock: black, tan or O.D. green (tested) synthetic: length of pull, 15”

Overall Length: 27" (with 16" barrel)
Weight: 7 lbs., 4 ozs.

Accessories: one 10-round magazine, instruction manual, cable lock (included); 3", 6" and 9" side mount Picatinny rails, left-hand bolt assembly, The Wilderness tactical sling, extra magazine, sling, cleaning kit, Pelican case (optional)

Suggested Retail Price: $1,995 (standard carbine with carry-handle/1.5X optic); $1,839 with 9" Picatinny top rail only $590
(extra barrel assemblies)