The Colt M4 Carbine is a gas-operated selective fire (firing options include semi-automatic and three-round while the M4A1 has a "full auto" option in place of the three-round burst) assault rifle that was developed and produced for the United States government by Colt Firearms in 1994, and is still in use today. The M4 and its variants are also used by several other countries around the world. It is a shorter and lighter version of the M16A2 assault rifle with highly modular capabilities, and is based on the original AR-15 made by ArmaLite. It is chambered for use with the standardized 5.56x45mm NATO cartridge an extremely common assault rifle round. The weapons standardized parts and ammunition combined with its almost limitless number of configurations make it the perfect choice for zombie warfare.

	The Colt M4A1 Carbine

The M4 is one in a long line of assault rifles in the M16/AR-15 family, thus most major design flaws have been worked out of the system. The M4 comes fully equipped with a flat top RAS (Rail Accessory System) on the receiver, and most models have a full RAS equipped fore grip allowing you to mount almost any weapon accessory made to the body of the gun (anything from M203 Grenade launchers, under-barrel shotguns, scopes, laser sights, lights, and grips). On the downside, the weapon's one major drawback is that it is susceptible to extreme heat conditions. Excessive fire of the weapon causes the all metal parts of its construction to warp slightly and jam. This is generally only reported during long engaging firefights, and is therefore easily remedied with proper shooting techniques.

The M4 sets itself apart from other assault rifles with its ruggedness and flexibility as a full weapons platform. With the proper modifications, it can be used for almost any situation. The weapon features a collapsible telescoping stock, which makes it ideal for close quarters combat, a situation you may find yourself in all too often when raiding buildings in search of food or supplies in zombie infected areas. The weapon's all metal construction also makes it highly durable for use as a bludgeoning weapon, but not as effective as other fixed or wooden stock rifles. The M4 is also highly accurate, especially when equipped with the proper scope or other aiming device. The 5.56mm ammunition it uses is nowhere near the highest on the stopping power charts, but it will easily get the job done.

	The Block I SOPMOD Accessory Kit for the M4A1

As mentioned earlier, the M4/M4A1 uses the 5.56x45mm NATO cartridge, a standard cartridge for NATO forces and for several nations not part of NATO. Ammunition is loaded into the weapon via a 30 round exchangeable and reusable clip. Other clip variations exist, including a 100+ round drum along with several other higher capacity ammunition boxes and several low capacity models such as 5, 10 and 20 rounds. The great thing about 5.56mm ammunition is that it is everywhere. Almost all law enforcement agencies use it, and it is the standard for most of the world's militaries. That means that in the event of an all out war with zombies, there will be no shortage of ammunition for your weapon. Another great feature about the military issue M4 is that it can use the civilian issue .223 Remington cartridges. The rounds are nearly identical in milling and specifications (although this is not recommended, it will work in a pinch). Again, this round is not the best rifle round when talking about stopping power, but it isn't the worst by any means either.

The M4 is fairly beefy. It weighs about 6.6 pounds (3.0 kg) fully loaded with a 30 round clip, and can easily weigh an additional 6 pounds (2.72 kg) with optional gear such as a M203 grenade launcher and scopes. On the plus side, it is only 29.8 inches (75.7 cm) in length with the stock collapsed, and can expand to an overall length of 33 inches (83.8 cm) with the stock fully extended. As with many carbines, the M4 is handy and more convenient to carry than a full-length rifle. In addition, the M4 comes standard with mounting points for a shoulder sling or 3-point tactical sling for easier carrying, along with an RAS mounted carry handle. The weapon also features several other optional accessories such as additional sling mounts, and tactical grips for additional firing styles.

There is nothing impractical about the Colt M4A1 Assault Rifle. It is an excellent and effective zombie weapon. It uses common ammunition and is very durable. There are endless custom modifications available to even further fine tune it to your needs. Lastly, it is fairly simple to operate and maintain.