The M4 is a lightweight, gas operated, air cooled, magazine fed, selective rate, shoulder fired weapon with a collapsible stock. A shortened variant of the M16A2 rifle, the M4 provides the individual soldier operating in close quarters the capability to engage targets at extended range with accurate, lethal fire. The M4 Carbine achieves over 80% commonality with the M16A2 Rifle and will replace all M3 .45 caliber submachine guns and selected M9 pistols and M16 rifle series.

The M4 is a shortened version of the M16A2 rifle, similar in appearance to the XM177 series of weapons. It has a 4-position, collapsible, telescoping butt, M16A2-style round handguard, and a detachable carry handle. The M4, like the M16A2, can fire in semi-automatic or three-round burst mode. The M4A1, like the M16A1, can fire in semi-automatic or fully-automatic mode. Both weapons use a detachable 30-round magazine and are chambered in 5.56x45mm NATO caliber.

The Special Operations Peculiar Modification to the M4 Carbine (SOPMOD M4) Accessory kit is a series of accessories developed for M4s and M4A1s belonging to units of the United States Special Operations Command (USSOCOM). These accessories include an ACOG (Advanced Combat Optical Gunsight) Reflex sight (non-telescopic), an ACOG 4X Scope, Visible Laser, IR Pointer/Illuminator, Quck Detachable Sound Suppressor, Visible Light, M203 Grenade Launcher with Quick Detachable Mount, Modified M203 Leaf Sight, and Rail Interface System (RIS).