The SIG Sauer SG551 is a switzerland-made select-fire carbine chambered in 5.56x45mm NATO, introduced in 1987. Primary use: military. Type: Carbine Action: Select-Fire Caliber: 5.56x45mm NATO Capacity: 30 Year introduced: 1987, Switzerland Weight: 112 oz Overall length: 37" Status: Active Intended use: military