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Microtech STG-556

by Greg Rodriguez   |  September 23rd, 2010 0


The futuristic-looking Steyr AUG is one of my favorite fighting guns. Although some have criticized its inability to be used from the weak side and the poor trigger necessitated by its bullpup design, the unflappable reliability of its gas-piston operating system and excellent close-quarters handling qualities have endeared it to many.

I owned an AUG, but I foolishly sold it some years back. Despite the handsome profit I earned, I regretted selling that gun until Microtech Small Arms Research (MSAR) announced the new STG-556 last year.

MSAR is a division of Microtech Knives, which has a reputation for producing the finest automatic knives on the market. Microtech has the expertise and production facilities, so it set up MSAR to provide an affordable, American-made AUG clone for the U.S. market.

MSAR’s new STG-556 rifle is built on an investment-cast receiver of 7075 T6 aircraft-grade aluminum. The receiver is held to very tight tolerances and is beautifully finished. Upon completion, it and all other mating components are Mil-Spec hard-coat anodized.

The new rifle resembles the original AUG, but there are some significant differences. Most notable among them are a forward assist and a bolt hold-open feature that locks the bolt back on an empty magazine. Heat-treated, steel hard points on the receiver for the attachment of Picatinny-spec accessory rails are another addition.

Other than these changes, the STG-556 is pure AUG, but I have to tell you that the STG-556 is built to tighter tolerances than the original. MSAR’s version retains the original’s chrome-lined, hammer-forged, quick-detach barrel in 14- (with appropriate NFA paperwork), 16-, or 20-inch lengths. To switch barrels, simply push the barrel release and twist the barrel. The barrel retains the original’s distinctive tulip-bulb-shaped flash hider. The fluting is MSAR’s addition.

The AUG came with an integral 1.5X optic with backup iron sights. MSAR’s version retains those, but the user-removable optic no longer has the original’s “donut of death” reticle. On the plus side, the new reticle, which adds a pointed post inside the circle for more precise shot placement at long range, is more versatile.

The STG-556 retains the AUG’s polymer stock, which may be ordered in black, tan, or green. The original AUG started the trend towards vertical foregrips, and Microtech’s version wisely retains this feature, as well as the crossbolt-style safety, located just behind the trigger.

Translucent magazines are built to AUG-spec but of a much tougher, chemical-resistant DuPont polymer. The STG-556 comes with a 10-round magazine, but 20-, 30-, and 42-round magazines are also available. Empty magazines do not drop free when the release lever, which is located behind the magazine well, is activated.

Like the AUG, the STG-556 employs a short-stroke, gas-piston operating system. The system is adjustable to allow for suppressed use or to compensate for a dirty gun. Its rotating bolt has seven locking lugs. The bolt is unlocked by a stud on the bolt body and a recessed cam guide on the carrier’s surface. The bolt carrier is guided by two rods inside the receiver, each with a recoil spring directly behind it, around individual spring guides. The bolt employs a claw extractor and a case ejector to keep the STG-556 chugging along.

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MSAR STG-566 ACCURACY

Factory Load Velocity (fps) 100-Yard
Accuracy (in.)
.223 Rem
CorBon 55-gr. BlitzKing 2944 2.21
Hornady 55-gr. TAP 3187 1.24
Federal 69-gr. Match 2894 1.87
Notes: Accuracy is the average of five, five-shot groups fired from a Caldwell rest with a rear bag at 100 yards. Velocity is the average of 10 rounds measured 15 feet from the gun’s muzzle with a Shooting Chrony chronograph.

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MSAR STG-556

Model: STG-556 Sporting Rifle
Purpose Tactical, home defense
Manufacturer: Mictrotech Small Arms Research
300 Chestnut St.
Bradford, PA 16701
814-363-9260
Action type: Semioutomatic
Operation: Short-stroke gas-piston; rotating bolt
Magazine type
and capacity:
Double-stack 10, 20, 30, and 42 rounds:
Receiver material: Investment-cast 7075 T6 aluminum
Calibers: 5.56×45/.223 Rem.; 6.8 SPC conversion kit available
Barrel material: 14, 16 (as tested), 20 inches
Rifling: Six grooves; 1:9 RH twist; LH available upon request
Sights: Integrated 1.5 X optical sight with open backup iron sights
Finish: Matte black, desert tan, or O.D green
Safety: Two-position crossbolt
Trigger Type: Two-stage, pull-through
Pull Weight: 9 pounds, 12 ounces (as tested)
Stock material: Impact-resistant synthetic
Length of pull: 5.25 inches
Checkering: Stippled
Buttpad: Black rubber
Sling studs/ swivels: Quick-detach front and rear
Weight, empty: 7.2 pounds
Overall Length: 27 inches( 16-inch barrel as tested)
Accessories: Owners manual, 10-round magazine; lock
MSRP: $1,995 with optics;
$1,839 with Picatinny rail

Like all bullpups, the STG-556 appears quite ungainly, but that opinion usually changes quickly once you’ve handle one. The bullpup’s primary advantage is its length. Because it employs a trigger-linkage system to mount the trigger ahead of the bolt, a bullpup is very short, even with a 20-inch barrel. This makes for a nimble, easy-handling package that sacrifices nothing in terminal performance, unlike some of its short-barreled competitors.

But those improved handling qualities come with two major tradeoffs. The first is a heavy trigger, which is almost unavoidable due to the length of the trigger linkage. The second is that a bullpup may only be fired from one side because the ejection port is right next to the shooter’s face when fired from the weak side.

The STG-556 can be converted to left-hand use, but whichever side you set up the gun for is the only way it can be fired without risk of injury. Still, for many uses, the incredible handling qualities and short overall length of the STG-556 more than outweigh the disadvantages of the bullpup configuration.

Shooting The STG-556
I must confess that I didn’t get too serious about shooting groups with the STG-556. After all, even with its fine point, the reticle on the carbine’s optic was not designed for benchrest work, and neither was the stock. Even so, I fired enough sub-2-inch groups to know this gun will shoot.


Though the low-power optic and large reticle are not designed for shooting tiny groups, the STG-556 produced some pretty respectable groups.

The STG-556 really shined from field positions and during rapid-fire drills. During one drill, I placed the bulk of a 42-round magazine into a group barely bigger than a softball, despite firing from field positions at distances that ranged from 15 out to 150 yards. With the aid of a truck bumper or trash barrel, centered, 100-yard mellon shots were a snap.

With the accuracy work out of the way, I moved to the 50-yard line for some rapid-fire drills. My training partner and I took turns running magazines through the carbine as fast as we could. After a total of 750 rounds, the gun was scorching hot, but the STG-556 never bobbled.

MSAR’s STG-556 is an accurate, reliable carbine with unmatched close-quarters handling qualities. It may look a little odd, but pretty is as pretty does, and to those who could benefit from an ultrareliable carbine designed to work in tight spaces, MSAR’s new offering is a beauty.

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