The M16A4 is the current standard U.S. Marine Corps issue service rifle, featuring a flat-top upper receiver, KAC RAS quad-rail, and 20-inch barrel. Full-auto military versions are restricted; commercial semi-auto variants are sold as collector pieces. Type: Semi-Auto Rifle Action: Gas-Operated Caliber: 5.56x45mm Capacity: 30 Year introduced: 1997, USA Weight: 8.8 oz Overall length: 39.5" Status: Active Military use: Yes Intended use: Military, Collecting