The M16A4 is the current full-length M16 variant, featuring a flat-top upper receiver with Picatinny rail for optics, a Knight's Armament RAS handguard, and the M16A2 burst-fire trigger group. Primary infantry rifle for USMC through the 2010s. Type: Semi-Auto Rifle Action: Gas-Operated Caliber: 5.56x45mm Capacity: 30 Year introduced: 2000, USA Weight: 8.8 oz Overall length: 40" Status: Active Military use: Yes Intended use: Military, Service Rifle