M4 vs AR15 - Comparison

M4 vs AR15 – Comparison

Two of the most popular rifles in production are the AR15 and the M4. Both are available in both automatic and semi-automatic versions. They are incredibly similar weapons which makes the comparison that much more important. In this article, we will consider the history and differences between the the M4 VS AR15 and decide on a winner later on.

  • AR15 History
  • M4 History
  • The difference between the AR15 and the M4
  • The Comparison

AR15 History

The AR15 is an air-cooled, gas-powered, magazine rifle. It is a selective-fire 5.56x45mm weapon that was designed to be a light-weight rifle. It was built to fire a lightweight, high speed small caliber round allowing more rounds per magazine. The design was based on the AR-10, and with a few modification it was taken on by the US military as the M16. The AR15 has gone on to be modified into several other similar weapons. This is the development process that has lead to the debate between the M4 VS AR15.

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During World War II, the US military was using the M1 Garand, the M3 “grease gun”, the Thompson submachine gun, the M1 and M2 Carbines, and the M1918 Browning Automatic Rifle. They wanted to replace all of these weapons with a single automatic rifle. Early efforts were disappointing. They rolled into the Korean War using the M2 most often, but popular opinion was that it lacked power. It was determined that an intermediate round was needed, so it was back to the drawing board.
Those in charge insisted on a single high-power .30 caliber round that could be used in the new automatic rifle as well as by the new machine gun they were designing. The resulting round was the 7.62x51mm round and the M14 rifle. The rifle was designed using the M1 Garand as a base, but it was given a 20 cartridge capacity and was made fully automatic. The M60 machine gun was also taken on for military use.

The M14 was quickly compared to the AK-47 as they faced each other in the Vietnam War. It was said that the M14 was very hard to control when being fired in fully automatic mode. In addition, it did not carry enough rounds to take on the superior AK-47. The M2 also fell short. Despite its ability to put out rounds quickly, it lacked power compared to the AK. The US military needed a hybrid between these two weapons.

The military had to take a step back to a request that was originally made by General Willard Wyman in 1957. He had asked the military to design a .223 caliber rifle with a 20 cartridge capacity that weighed under six pounds. He wanted the round to bust through a standard military helmet at 500 yards. It also needed to maintain a muzzle velocity above the speed of sound and beat the stopping power of the .30 Carbine. Following these parameters, the AR15 was born.

Colt purchased the design from ArmaLite in 1959 and started a huge marketing campaign overseas. This happened after ArmaLite was faced with some financial issues. The weapon was highly popular during a tour in the East, and Colt closed a deal with Malaya later that year. They started producing the AR15 and selling to military services all over the world. Without this move, we would likely not be discussing the AR15 VS the M4.
The weapons thoroughly impressed General Curtis Lemay the following year during a weapons demonstration. He was promoted to US Air force Chief of Staff shortly after and placed an order for 80,000 of the weapons. However, General Maxwell Taylor was uncomfortable with having two different calibers in the military and went over his head to shut down the order. President Kennedy sided with General Taylor. Then in 1961 the Advanced Research Projects Agency sent ten AR15s to South Vietnam. William Godel was in charge of this move, and the weapons were a hit. They sent another 1,000 to South Vietnam the following year. Special Forces officers could not get enough, and started pushing for a full scale switch to the AR15.

The wound cavity created by the AR15 rounds was impressive, but was thought to be due to the tumbling motion of the bullet caused by the subtle rifling of the barrel. The wounds were so large that the pictures were classified until the 1980s. What was determined was that any pointed bullet with a lead core will have this motion because the bullet is heavier to the rear. In this case, these gaping wounds were created by bullet fragmentation. The rifle was firing these rounds at a speed that caused them to break apart when contacting human flesh.

The AR15 faced a great deal of bias as it tried to take the US military by storm. The Secretary of Defense Robert McNamara was forced to look at an ARPA report stating that the AR15 was the dominant weapon but also reports from the Army stating that the M14 was dominant. President Kennedy wanted answers, so Army Secretary Cyrus Vance was asked to test both weapons against the AK-47. The Army again sided with the M14, but nobody was surprised. Vance felt that the testing methods were biased and had the Army Inspector General confirm his theory. Sure enough, he found that the tests were rigged.

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In 1963, reports were filed that confirmed that the AR15 was superior to the M14. All M14 production stopped, and the AR15 was passed the crown. It was the first universal infantry weapon to be issued to all US military forces. However, there were reports of several issues with the weapon including the lack of a chrome plated chamber. Before adoption, the weapon was modified by moving the charging handle from under the carrying handle to the back of the lower receiver. It was renamed the M16 for military use. However, they still did not implement a chrome plated barrel. The military did insist on a forward assist to push the bolt into the battery in case a round did not seat in the chamber. There was push back from Colt as well as from the Air Force as this was seen as unneeded and overly expensive. Because of this, the Air Force received M16s without the forward assist and everybody else got the modification.

At the end of 1963 McNamara finalized the shipment of 85,000 M16s. In addition, General LeMay requested an addition 19,000 of the Air Force version. The following year they received their order, and the year after they received an additional 57,240 rifles. In addition, the Secret Service and other federal law enforcement have since adopted the AR15. Colt also created a semi-automatic version for civilian use. Now we can understand the difference between the AR15 and the M4.

M4 History

The M4 rifle is a lighter and shorter version of the AR15. This is the simplest way to compare the AR15 versus the M4. It is a 5.56x45mm, air cooled, gas operated weapon. It has direct impingement and is magazine fed. The original barrel was 10 inches and it has a telescoping stock. The weapon is used by the US Armed Forces and has recently been replacing the AR15 as the primary infantry weapon. This weapon can also be mounted to the M203 and M320 grenade launchers. It can be fired semi-automatic or in three round bursts, but there is also a version called the M4a1 that can fire in fully automatic.
After the AR15 was adopted by the US military, carbine options were brought on for special operations. This group of weapons was used throughout the Vietnam War. However, there were some design flaws. It was thought that the barrel length was ruining the ballistics and degrading the accuracy and range of the weapon. It also caused more muzzle flash so that a larger suppressor had to be installed. Despite these issues, it was considered an ideal close- quarters weapon as a submachine gun. In 1988, Colt started working on the newest M4 called the XM4 which featured benefits of the AR15 and the Colt Commando.

This version was given a 14.5 inch barrel with the same rifling as the AR15. It uses 62 grain M855 cartridges. The longer barrel made the XM4 more effective and gave it a smaller muzzle blast. It also allowed the option of mounting a bayonet and a grenade launcher to the weapon. It was given an improved rear sight and a cartridge deflector as well. In 1994 the US military brought on the XM4 to replace the AR15 in specific roles. It has also been swapped out for most submachine guns and handguns in US military service. It has been concluded that this weapon has more stopping power and penetrating power than any other option available. This revised version gives serious competition in looking at the differences between the M4 VS the AR15.

The Comparison – AR15 VS M4

In the end, the debate between the AR15 and the M4 is a fairly simple argument. When you look at the evolution of these weapons, you can see that the M4 is more evolved than the AR15. There is a reason why the US military has adopted this weapon over their M16. It is smaller, lighter, and just as effective. While there is normally a heated debate when comparing these types of weapons, this one is pretty obvious. The clear winner is the M4. I hope this has helped with your personal comparison, and hopefully has helped you make a better purchasing decision.

1 comment
  1. Well it’s clear you’re using heavily dated information about the AR-15. Because modern AR-15s are carbon copies of M4s. If you don’t know to look for the selector you’d never tell them apart. The good ones do have chrome lined barrels, are hbar, etc.

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