The HS Produkt M21 is a Croatian bullpup semi-automatic rifle chambered in 5.56x45mm NATO. A compact design derived from military development, the M21 features a folding stock and accepts STANAG-compatible magazines. Type: Semi-Auto Rifle Action: Gas-Operated Caliber: 5.56x45mm Capacity: 30 Year introduced: 2005, Croatia Weight: 7.7 oz Overall length: 27.5" Status: Active Military use: Yes Intended use: Duty, Collecting