- Main article: M4A1 (TLS1)
- Main article: M4A1 (TLS2)
- Main article: M4A1 (TLS:UC)
- Main article: M4A1 (TLS:DZ)
The carbine version of the M16 is a prized weapon for many elite military/paramilitary units, due to its modularity and its versatility in both close quarters and open field combat. The weapon's popularity has since spread to the regular U.S. infantry, who increasingly find themselves deployed to dense urban environments.
Used extensively by many law enforcement authorities, S.W.A.T. units, and militaries around the world.