The German defense company Rheinmetall has teamed with Austrian arms manufacturer Steyr Mannlicher to manufacture and market the RS556 – a German version of the 5.56mm x 45 cal. modular assault rifle system based on Steyr’s STM556. The Austrian weapon was first unveiled in 2012. Eying the German market, Rheinmetall positions the new weapon as a candidate for the German “System Sturmgewehr Bundeswehr” – the planned replacement of the G36 – the standard German military assault rifle made by Heckler & Koch. This project is set to begin in 2019. Rheinmetall will offer the new assault rifle as a joint program, locally produced (made in Germany), with a German value-added share of 60%.
Featuring an adjustable short-stroke gas piston system and rotating bolt, the gas-operated RS556 is based on the tried-and-tested Steyr Mannlicher Universal Army Rifle (AUG). With a 16″ barrel (406 mm) and a fully loaded, 30-round magazine, the RS556 weighs around 4.2 kilograms, (just over 9 pounds.)
In a matter of seconds and without tools, the hammer-forged barrel can be easily exchanged. A number of standard barrel lengths are available (14.5″, 16″, 18″ and 20″); and, according to the company, customer-specific barrel and rifling lengths can be easily created. A special breech system with an emergency operation feature ensures that the weapon always functions reliably even under extreme operating conditions, e.g. in severely hot and cold environments.
The adjustable-length light-weight stock clicks into seven different positions, meaning that operators can adjust the RS556 to match their individual equipment profile in an optimum fashion.
The RS556 is compatible with Rheinmetall’s modular “Future Soldier – Expanded System” (IdZ-ES), and can also be integrated with other soldier systems. The weapon has multiple standard and optional NATO accessory rails with receiver systems designed per MIL-STD-1913, STANAG 2324 and STANAG 4694, enabling soldiers to fit their weapons with various optics, night observation devices, and laser light modules. A 40mm grenade launcher can also be mounted on the new assault rifle.
Since entering service in 1997, the G36 became a favorite weapon in service with numerous military and law enforcement forces around the world. However, after experiencing overheating in extended firefights, the G36 proved unsuitable for long range engagement in hot conditions. After a thorough investigation that lasted three years, the German Ministry of Defense decided to phase out the G36 over these concerns.  Heckler & Koch contested the decision claiming the German Defense Ministry did not provide clear specifics for the weapon.
