STG-556

The STG-556 is a Steyr AUG A1 clone manufactured by Microtech Small Arms Research (MSAR). It was introduced at the 2007 SHOT Show. The STG-556's working system features a bolt release as seen on the M16 rifle; otherwise, the STG-556 retains the features similar to the Steyr AUG, such as having the quick-change barrel option and the ability to change which side the weapon ejects from by changing the bolt out for a right or left side bolt respectively. There is some parts interchangeability but the rifle is not a true clone. The STG-556 ships standard with right side ejector. The STG-556 is unable to use M16-style magazines or STANAG NATO standard magazines; they use versions of a proprietary MSAR magazine resembling the Steyr mags. The current production XM-17 E4 use STANAG magazines. The STG-556 is a short-stroke gas piston. The STG-556 rifle can be converted from either having a telescopic sight or a MIL-STD-1913 rail. It is available in civilian (semi-automatic only) and military/law enforcement (select-fire) variants.
A limited edition STG-556, a clone of the Steyr AUG A3, had a production run of only 1,000 rifles. There was a limited production of 232 rifles produced with an 18.5" heavy barrel after tests proved that length provided optimum accuracy over the 24" length due to barrel harmonics. Another limited edition Steyr AUG A3 clone, the STG-556 Gebirgsjäger, had a production run of 500.
MSAR's last model was the STG-556 XM17-E4. The STG-556 XM17-E4 was introduced at the 2009 SHOT Show. It can use AR-15 and M16 magazines.
MSAR closed down permanently on 3-20-15. No specific reasons were stated on their website, but it is well known that Steyr setting up a US based manufacturing arm, producing genuine Steyr AUG firearms, all but eliminated the need for anyone to buy a clone. When MSAR started, and for several years following, there was no way for a US Resident to buy a new Steyr AUG, only AUGs (and USRs) that had been imported prior to the final Clinton executive order which banned further importation of the neutered USR.
Similar US weapons.
The TPD USA AXR revealed at the 2007 SHOT Show, manufactured by Tactical Products Design Inc., is a similar weapon.