A compact version of the M-16, the M4 carbine is commonly used when the firepower of an assault rifle is needed, but the weight and size is not. it is commonly used by US and Israeli special forces. The M4 has selective fire options including semi-automatic and three-round burst (like the M16A2), while the M4A1 has a "full auto" option in place of the three-round burst. The M4 is gas-operated, air-cooled, magazine-fed, selective fire, shoulder-fired weapon with a telescoping stock. The M4 Carbine achieves over 80% commonality with the M16A2 rifle and was intended to replace the .45 ACP M3 submachine guns, The M4 Carbine is also capable of mounting the M203 grenade launcher.

However, there have been some criticisms of the carbine, such as lower muzzle velocities and louder report due to the shorter barrel, additional stress on parts because of the shorter gas system, and a tendency to overheat faster than the M16A2.