History

The M16 assault rifle was originally designed in 1957 by Eugene Stoner as the AR-15, a 5.56x45mm variant of his earlier, and unpopular, AR-10 rifle in 7.62x51mm. It was accepted by the U.S. Army in 1961 and saw use in Vietnam, where it was generally unpopular due to fouling problems caused by the weapon's direct gas impingement system and the adoption by the United States Army of a new type of propellant the weapon wasn't originally designed to use. In addition, the weapon was distributed along with literature that stated that minimal or no cleaning was necessary, which turned out to be false. This led to the design and adoption of the M16A1, which featured a forward assist. This feature, combined with regular maintenance of the weapon, helped alleviate jams and other problems caused by fouling.
The M16A2 rifle was adopted in the 1980s. This variant replaced the fully automatic capability of the M16A1 with a three-round burst option, in order to conserve ammunition while still providing troops with ample firepower. The M16A2 was followed by the M16A3, which reverted to the full-automatic option. It was not adopted in large numbers.
The current version, the M16A4, features a Picatinny rail for different sighting solutions, and retains the three-round burst option of the M16A2, replacing the full-auto option of the M16A3. It also features a rail under the handguard for other attachments.
The M16A4 is currently used by the United States Marine Corps, and it and its variant, the M4 Carbine are in wide use by United States military forces.

Singleplayer

The M16A4 can only be picked up during War Pig (level). It is dropped occasionally (and sometimes with the M203 grenade launcher) by incapacitated Marines and always with iron sights. The M16A4, in single player, has a fully automatic firing mode, which is inaccurate, as the real-life M16A4 does not feature full-automatic fire.

Multiplayer

Weapon: M16A4
Accuracy: 10 / 12
Damage: 7 / 12
Range: 9 / 12
Fire Rate: 9+ / 12
Mobility: 8 / 12
Clip Size/Reserve Ammo: 30/60
Recoil: low cluster
Reload Time: 2 seconds / 2.365 empty
Damage: 30-40
Range: 1500-2000 / 500-1000 SD
Rate of Fire: 925 RPM
Penetration: Medium / Large Bullet
Location Damage Multiplier: Head (1.4) / Neck: (1.0) / Torso: (1.0) / Stomach: (1.0) / Limbs (1.0)
Hip Accuracy: Stand (3-7) / Crouch (2.5-6) / Prone (2-5) Unlocked: Level 1. (Assault Rifle Class)

Incredible accuracy and damage values, the only drawback being that it is not fully automatic, firing in three round bursts. Within each burst though the bullets come flying quite rapidly at 950 RPM, but once you take into account the pauses between each burst it slows to 450 RPM. That single three round burst will is guaranteed to take down an enemy with Stopping Power equipped, and without it your odds of a kill are still quite good. The slow bursts can even be a blessing for players new to Call of Duty. It brings down recoil, conserves ammunition and allows you a clear view without muzzle flash between each shot.

As mentioned above, with Stopping Power, this gun kills in one burst if all bullets hit the target. Therefore, quick aiming skills are needed in order to succeed, since this gun cannot spray and pray like full automatic weapons can. If you miss your first burst, you will need to wait slightly before you can fire again, making it highly unforgiving.

Also, it generally wastes ammo since one click of the trigger shoots out 3 bullets. This gun has excellent accuracy and range, so it can be successful at far and medium ranges, however, it is hard to use this gun close range when you begin. So when facing an enemy up-close and personal, try firing from the hip and slamming your finger on the trigger as fast as you can.

Challenges