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/Co-Op

The M16 is fully automatic in the campaign. It is the starting weapon in Operation 40 where it is equipped with an ACOG scope and M203, as well as being the starting weapon in "S.O.G." where it is equipped with a Masterkey. It can be found throughout "S.O.G." with different attachments.

The M16 is available in Nazi Zombies, it can be bought off the wall for 1200 points. Similar to Multiplayer, it is a 3-round burst weapon. When upgraded in the Pack-A-Punch Machine, it becomes "The Skullcrusher," making it fully automatic, increasing damage, and adding an under-barrel M203 Grenade Launcher.

Multiplayer

Damage 40-30
 
Damage Multipliers Head: 1.4, Body: 1, Limbs: 1
 
Magazine Size 30 rounds (45 Extended Mags) (SP,MP,Z)
 
Tier 9
 
Unlocked at 1
 
Cost 0
 
Cost  1200
 
Starting Ammunition 90
 
Maximum Ammunition 240
 
Reload Time 2.03 loaded, 2.36 unloaded 
  
Recoil Low
 
Penetration Moderate
 
Fire Mode 3 round burst (MP) Automatic (SP)
 
Used by SOG, USMC, Op 40

The M16 fires in three-round-bursts in multiplayer, like the M16A4. It is part of the default "Assault" class. After having unlocked Create-A-Class, it does not need to be purchased with CODPoints.

The weapon has high damage but high recoil, offset by mechanical burst-fire, meaning it is most effective at medium-long range, especially since it maintains its damage up to longer ranges than most other assault rifles. However, the forced delay between each burst makes it less effective than automatic weapons at close range.

Challenges