The M4 Carbine is a shorter, and lighter version, of the M16A2 assault rifle. As with many carbines, it was meant to provide troops with an effective, shoulder fired weapon in lieu of pistols, such as the M9. Since the weapon is shorter, it is handy and more comfortable to carry than full length rifles. While this makes it a candidate for non-infantry troops (vehicle crews, clerks and staff officers) it has been used by US Special Operations Command (SOCOM) and others seeking a compact weapon for close quarters combat.
The M4/M4A1 5.56mm Carbine is a gas operated, air cooled, magazine fed, selective rate, shoulder fired weapon with a collapsible stock. A shortened variant of the M16A2 rifle with a 36 cm barrel, the M4A1 provides the individual soldier operating in close quarters the capability to engage targets at extended range with accurate, lethal fire. The original M4 Carbine had "semi" and three round burst fire modes, while the M4A1 has "semi" and "auto" but no three round burst. The M4A1 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 M4A1 is favored by the U.S. Army's elite Delta Force, the Australian Special Forces, South Korea, and the infantry forces of several other countries. Capable of mounting the M203 Grenade Launcher, the M4A1's reduced size and weight offers a potent package for the urban warrior. The M4A3, which is the newest variant, has an accessory rail for mounting among others the Advanced Combat Optical Gunsight (ACOG) and various Aimpoint red dot sights.
The M4A1 Carbine is specialy favored by CT and SF units because of its compactness and firepower that the rifle offers for close quarter combat (CQB). It is very useful in urban warfare. Although M16 is prefered for mid-long distance shooting, the M4A1 is more comfortable to handle and more reliable than the old M16.
Some features compared to a full length M16A2 rifle include:
- Compact size
- Shorter barrel
- Collapsable butt-stock
- Higher rate of fire
- Selective full-automatic rather than three shot bursts (M4A1)
Like all the variants of the M16 assault rifle, the M4 Carbine and the M4A1 Carbine can be fitted with many accessories such as night vision devices, laser pointers, scopes, bipods and the M203 grenade launcher.
To load an M4 or M4A1 for (semi)automatic fire: Point the muzzle in a safe direction. Cock the gun, making sure that this also opens the bolt. Put the selector lever on SAFE. Open the bolt and check the chamber to ensure it is clear. Insert the magazine, pushing it upward until the magazine catch engages the magazine. Tap upward on the bottom of the magazine to ensure it is seated. Chamber a round.
To chamber a round: Ensure that the bolt is closed. Once you have done that, pull the charging handle to the rear as far as it will go. Release the charging handle. Let it return on its own, do not ride it. Tap the forward assist to ensure the bolt is fully forward and locked. Place the selector lever on the desired mode of fire. If the carbine is not to be fired immediately, put the selector lever on SAFE and close the ejection port cover.