Steyr STM556
Steyr Mannlicher · Assault Rifle · In Production · 2012
Also known as: STM-556, RS556, Rheinmetall-Steyr RS556
Overview
The Steyr STM556 is a select-fire assault rifle chambered in 5.56x45mm NATO, produced by Steyr Mannlicher GmbH since 2012.
Specifications
| Weight (empty) | 3700 g (130.5 oz) |
| Weight (loaded) | 4180 g (147.4 oz) |
| Overall Length | 960 mm (37.80") |
| Folded Length | 860 mm (33.86") |
| Barrel Length | 406 mm (15.98") |
| Action Type | Gas Operated Short Stroke Piston |
| Firing Mechanism | Hammer Fired |
| Trigger Type | Single Stage |
| Magazine Capacity | 30 rounds |
| Magazine Type | Detachable Box |
| Muzzle Velocity | 884 m/s (2900 fps) |
| Muzzle Energy | 1563 J (1153 ft·lbf) |
| Effective Range | 500 m (547 yd) |
| Maximum Range | 3600 m (3937 yd) |
| Rate of Fire | 700 rpm |
| Barrel Rifling | Right Hand |
| Rifling Twist | 178 mm (7.01") |
| Number of Grooves | 6 |
| Frame Material | Aluminum Alloy |
| Barrel Material | Steel |
| Stock Material | Polymer |
| Finish | Matte Black |
Calibers
- 5.56x45mm NATO · primary · 5.56mm NATO — also known as 5.56x45mm, 5.56 NATO
Features
- Firing modes: Semi Automatic, Full Automatic
- Feed systems: Stanag Magazine
- Safety mechanisms: Ambidextrous Selector Lever, Firing Pin Safety
- Features: Quick Change Barrel System, Monolithic Upper Receiver, Full Length Picatinny Top Rail, Ambidextrous Controls, Short Stroke Gas Piston, Manual Gas Regulator, Stanag Magazine Compatible, Six Position Adjustable Stock, Cold Hammer Forged Barrel, M Lok Handguard, Tool Free Barrel Swap, Dry Lubrication
Variants
- Rheinmetall-Steyr RS556 — Military Variant
Service history
Operators
- Austrian Armed Forces · as STM556
Production
Production years: 2012-present
In production; competes internationally in military rifle trials
Origin
Country of origin: Austria
Notes
The STM556 was designed to compete in the growing market for modern AR-15 pattern rifles enhanced with piston-driven reliability. Its key differentiator is the barrel quick-change system inherited from the Steyr AUG, allowing barrels to be swapped in under a minute without any tools - a feature unmatched by most competitors. The rifle uses a two-piece aluminum alloy receiver connected by cross-pins, with fully ambidextrous controls throughout. Barrel lengths range from 293mm (11.5 inches) to 550mm (22 inches), making the platform highly adaptable. In 2016, Rheinmetall partnered with Steyr to offer the RS556 variant in the German Bundeswehr competition to replace the HK G36. Cold hammer-forged barrels and a proprietary dry lubrication system contribute to the rifle's durability in adverse conditions.
Background
The STM556 represents Steyr's acknowledgment that the bullpup AUG, while revolutionary in the 1970s, was losing ground to conventional AR-15 layouts in international military trials. Rather than abandon the AUG's innovations entirely, Steyr transplanted its best features - the quick-change barrel, the piston system, and Austrian engineering precision - into the AR platform that had become the global standard for modern infantry rifles.