M-16A1 - The first version to become the primary assault rifle of the US Army, the M-16A1 is fully automatic and lightweight. The variant was heavily used in the Vietnam War.
M-16A2 - Introduced in the 1980s to replace the M-16A1, the A2 replaces the A1's fully automatic capability with a three round burst fire mode and added sturdier parts.
M-4 carbine - The M4 is a shorter and lighter variant of the M-16A2. The rifle is widely used by the U.S. military and will eventually replace the M-16 rifle for most combat units in the United States Army.
M-16A4 - The fourth generation of the M16 series, it is equipped with a removable carrying handle and a full length quad Picatinny rail for mounting optics and other ancillary devices. The rifle is currently standard issue for the U.S. Marine Corps.
- In El Contador, Archer wields an M-16A1 with a 20-round magazine.
- The rifle also appears in Drift Problem , Smuggler's Blues , The Rules of Extraction , and On The Carpet .
- In several episodes, two M-16A2s can be seen on the wall in the ISIS armory.