M16 Assault Rifle

The M16A3 assault rifle is a Tier 2 replacement for the Submachine gun with higher damage and better accuracy. It holds 50 rounds with a 360 round reserve, having less total ammo than the Uzi, but being a better overall weapon. The M16 is the best choice as a general use firearm, as it is adaptable to most situations.

Tactics
The assault rifle is a weapon that is mostly effective in medium-range combat, as opposed to the short-range auto shotgun and the long-range hunting rifle. It is a very flexible weapon, however, adept at picking off Special Infected from a distance and piercing multiple Common Infected. It has quite a high piercing power, but not quite as high as the hunting rifle. Its high piercing power makes it is a useful weapon for clearing rooms full of Infected or destroying oncoming Hordes.

With Valve's recent update reducing auto shotgun damage against a Tank and the assault rifle's high medium-range accuracy, the assault rifle has overtaken the auto shotgun as a weapon of choice for killing a Tank. The auto shotgun is still just as useful against nearby Infected, and in close quarters weapon choice lies to player preference.

Assault rifle ammo is easy to waste. The weapon trades ammo capacity for accuracy and damage, and this must be used to full advantage to be effective. The assault rifle generally needs only two or three shots to do its job, and any more hampers its accuracy at mid to long range. Thus, burst firing or "headhunting" is highly recommended at medium to long ranges as this not only helps to improve accuracy, but this also has the benefit of conserving precious ammo. A technique that seems to work pretty well on Xbox 360 to conserve ammo is to do a quick full trigger squeeze, which will fire 2 rounds. This can be useful when shooting long range and is effective on most difficulty settings except for expert.

While this weapon may be useful on higher difficulties because of its tighter cone of fire being safer when firing near other Survivors, this weapon struggles to keep up with the increased health of the Common Infected, requiring 4 bullets to kill one on expert, whereas a single shot from the other two weapons is still a kill. Additionally, the mid-range effectiveness of the assault rifle is shared with the pistols, meaning that taking the assault rifle sacrifices some flexibility.

In a group of four on finales, it's a good idea to have two people with Auto Shotguns and two people with Assault Rifles, get in a closet or similar point which causes the Infected to file in slowly, the two people with the shotguns crouch and shoot or melee, while the two people with the assault rifles stand behind them and fire rounds into the Infected as they approach. Be careful to note when the Tank comes, however—a Tank can easily destroy a group of four Survivors hiding in the same closet. It's best to run out and kill it in open ground, and return to the former spot when the Horde has come back.

Power Shot
A glitch in the game has been discovered which allows the assault rifle to shoot an entire clip of ammo in one shot. You can accomplish this by switching to your pistols and holding melee, switching back to the Assault Rifle (while still holding melee), then holding down shoot along with melee, after 8 seconds letting go of melee while still holding shoot. If done correctly a powershot will be fired.


 * Doing this glitch will leave you vulnerable until you fire or switch out your gun.
 * Best uses for this glitch would be killing far ranged enemies in one hit, the Witch in one hit, or taking down the Tank with 3 hits.
 * This glitch will also cause your rifle to reload nearly instantly if you "charge" it long enough.

Left 4 Dead 2
It appears there will be two new Assault Rifles in Left 4 Dead 2, a FN SCAR and an AK-47 variant. The SCAR seems to be the same as the L4D1 rifle, but the AK-47 has a 40-round magazine and a slightly-longer reload time.

Trivia

 * The in-game texture states that this rifle is produced by the fictional company American Armory as the M16A2.
 * The M16 class of rifles are the standard issue service rifle of many militaries, including the United States. It fires the 5.56mm NATO rifle round.
 * It is based on the M16A3. The M16A3 rifle is an M16 class rifle with fully automatic fire mode replacing the 3 round burst used on the M16A2.
 * In real life the original M16, M16A1 and M16A3 models were fitted with full automatic capabilities. The M16A2 and M16A4 models were fitted with the three round burst mode.
 * It has 360 reserve ammo, so it may have originally had a capacity of 30 rounds. Also note that the magazines that are used in the weapon model are 30-round magazines.
 * The Assault Rifle is based on Counter-Strike ' s M4A1 assault rifle. Its "price" in the gun's weapon file is the same as the M4A1's, and it references the M4A1 in its "animation" listing.
 * Valve took Counter-Strike ' s M4A1 un-silenced fire sound, recycled and edited it, and used it for Left 4 Dead ' s assault rifle.
 * If you look closely, the rifle has an A2 model upper receiver and an A1 model lower receiver. This explains why the rifle can fire full-auto. The U.S. Navy SEALs use this layout for their stock of M16 style weapons. They took fully-automatic capable A1 lower receivers and combined them to A2 upper receivers.
 * The M16 was the standard American weapon during the Vietnam War, of which Bill is a veteran. This could explain why he chooses this gun whenever given the opportunity.
 * The assault rifle shown in Left 4 Dead 2's E3 2009 demo appears to be an FN SCAR, and also appears to be more accurate in comparison to the assault rifle in the prequel.