The Colt XM177E1 is a usa-made select-fire carbine chambered in 5.56x45mm NATO, introduced in 1966. Primary use: military. Type: Carbine Action: Select-Fire Caliber: 5.56x45mm NATO Capacity: 30 Year introduced: 1966, USA Weight: 86 oz Overall length: 39.5" Status: Discontinued Intended use: military