What Is The Difference Between A M16 And An AR-15?

Both an M16 and an AR-15 have the same roots, but they vary in terms of applications and compatibility for more people. For example, the AR-15-style semi automatic weapon, which is the civilian rifle, has more aftermarket parts. In this case, they can always opt to assemble the right gun for them.

Now if you were looking to add a weapon in your collection and are torn between the M16 and AR-15, you’re not alone because many are also looking for enlightenment. To help you decide, let’s answer the question “what is the difference between an M16 and AR-15?

M16 and AR-15 History

Originating in 1956, the AR-15 was developed by Eugene Stoner.  He worked for ArmaLite, a small firearms company in the US.
This gas-operated semi-automatic rifle, which is lightweight being made of polymer and aluminum, was engineered and chambered for the .223/5.56.

This rifle was developed for the military. However, the company didn’t have much success.  That’s why they sold it to Colt, which the military had chosen in 1963 to create an automatic firearm.

Colt produced the automatic firearm that they named the M16. This replaced the M14 and was chosen as the official and standard issue rifle during the Vietnam War.

At the time of its introduction on the market, it was considered innovative and game-changing because most of the firearms back then were made from steel and wood.

A bit about the M14: This automatic firearm was chambered in .03-06 that’s known to generate heavy recoil.

Colt made use of the lighter recoil and weight of an AR15 with the M14’s automatic firing feature. They made only a few tweaks in the internal components of the AR-15.

Using the successful result they had made from this development, they started producing a lot of AR-15 semi-automatic. To reach more customers, Colt made the rifle also available for civilians and gun enthusiasts.

Meanwhile, the M16 is considered a popular semi-automatic weapon, which has been adapted by different armed forces, having about eight million rifles being produced. This rifle is in fact known as the most produced 5.5 caliber in history. However, it’s becoming obsolete for the lighter and shorter M4 carbine.

On the other hand, the AR-15, which more than 10 million units are civilian-owned, becomes a go-to rifle in the US. This rifle is for applications, like varmint hunting, target practice, and shooting competitions,

What are the differences between the M16 & AR-15?

Their appearances look the same when you first look at them, and you might not be able to distinguish which is which. However, the rifles, which are both popular, also have their differences in certain aspects.

Kit for the lower parts

Both rifles have different lower components kits, which include parts like the safety selector lever, disconnector, hammer, and trigger.

Lower parts of an M16 uses a different disconnector, trigger, safety selector lever, and hammer aside from its auto sear that is what delivers a fully automatic fire and 3-round burst.

Meanwhile, the AR-15, which is semi automatic, cannot offer these functions. It can only provide one round per squeeze of the trigger.

Lower receiver

AR-15’s lower receiver have different dimensions for its internal components that make it incapable of accepting the auto sear of an M16.


The design of the bolt of an M16 is slightly different from the “commercial bolt carrier group” of the AR-15. This allows the M16 to deliver a fully automatic function.

At the rear of an M16 rifle, there is an additional mass, which is what engages with the rear, while reducing recoil when the firearm is in automatic.

What are common between M16 and AR-15?


The barrel in the AR-15 platform can be chambered using different calibers.

The M16 fires the 5.56 NATO, and many AR-15 rifles are chambered for .223/5.56, so they can use .223 Remington or NATO rounds.

However, rifles chambered specifically for .223 shouldn’t be loaded with 5.56 because the rounds produce different pressure amounts.

Gas tube

It can direct the hot gas back to the rifle’s upper receiver. This will push the bolt backward and will extract a used casing.

Gas block

When a round is fired, the AR-platform rifle releases gas through a small hole in its top. This gas block works by catching and directing gas to cycle the bolt.

Charging handle

The bolt handle/cocking handle is the one that is what pulls the “bolt carrier group” back in order to cock the rifle’s hammer.

Firing pin

It pierces the rifle’s primer once the hammer’s released.

The following components can also be identical in the AR-15 and M16’s lower receiver

Grip of the pistol: This component is connected to the rifle’s lower receiver, enabling the firearm user to grasp and then fire the rifle.

Buttstock: A lot of civilian rifle owners choose to fit their platforms with a fixed stock, which is a classic military style stock.

Buffer and buffer tube: The AR rifle has a buffer system that can minimize recoil, making it an appealing design.

Recoil spring: It is in the buffer tube and is what’s compressed when the gas moves the bolt in the rearward direction. It will then push the rifle’s bolt forward towards the back again in order to load the upcoming round when it reaches its peak compression.

Upper receiver

The M16 and mil spec AR make use of forged 7075-T6 receivers. However, most AR-15 barrels are using 4150 (CMV) steel which is used in the barrel of an M16. These firearms also use the same stainless steel components in their gas tubes and firing pins.

Still, many AR-15 rifles are using the front sight post or gas block combo of the M16, and most AR-15 rifles are also using a bolt carrier group of an M16.

M16 and AR-15 share the following in their upper parts:

  • Gas block
  • Gas tube
  • Bolt
  • Barrel
  • Firing pin
  • Charging handle

Lower receiver

Both rifles share the following in their lower receivers.

  • Castle nut
  • Recoil spring
  • Buttstock
  • Buffer tube
  • Pistol grip
  • Buffer

Both rifles are using polymer buttstock, forged aluminum, and forged buffer tube.

Use and purpose

The M16 is still active in the military service even if M4 has been slowly replacing it. Even so, it still was the standard rifle of the US Armed Forces for about half a century. It was used heavily in the Vietnam War and in Afghanistan and Iraq.

However, M16 had reliability issues that surfaced due to harsh conditions in the jungle, so these were corrected. The cartridge of the rifle has been improved to enhance its function.

Aside from being heavily used in the US Armed Forces, it was also used by other armed forces all over the world, again making it the most common 5.56x45mm rifle that was manufactured in the world.

It’s used by NATO’s member countries and other nations. Across the globe, there have been eight million of these rifles that have been manufactured.

The military style version has driven the popularity of AR-15, which is AR-10’s scaled down version.

AR-15’s military version features “Select Fire” that allows users to easily switch between burst fire, automatic, and semi-automatic. For different purposes, the AR-15 has still been heavily used by both the military and civilian users.

Precision and range

The M16 is precise for a standard issue rifle for the US military in that it can produce light recoil while with high velocity or flat trajectory fire that can complete a head shot from 300 meters.

The newer versions are better at this, though, because they can offer an increased range with precision to 600 meters. Its latest edition, on the other hand, offers a lethal range 1,000 yards or less.

Meanwhile, the AR-15 is known as an accurate assault rifle for its lower bolt thrust and free recoil.

Tests also revealed that the AR-15 can fire between 600 and 700 rounds per minute, all while having a low jamming chance.

When it comes to firing distance, it varies significantly depending on the shooter’s marksmanship and skill, caliber ammunition,and rifle’s makeup.

Summing up, the .223 chambered military spec AR-15 can reach from 400 to 600 yards.

Which Rifle Is For You?

Since most states don’t permit civilians to buy and own an M16, most gun users choose the AR-15. And from 1986, M16 was banned for civilian purchase. The M16 can also come with an expensive price of at least $25,000.

And even if one would have the budget and be lucky to buy an eligible M16 on the market, they still need to do additional work like filing paperwork to comply with the ATF and paying additional fees.

On the other hand, the AR-15 is legal for civilian purchase in many states, even if some locations impose some rules on how one can only be configured. This rifle is still in production, too; thus, finding one wouldn’t be that hard.

But if you still want a piece of history in an M16, you can assemble an AR-15 with some M16 style parts, all without the high price tag and more paperwork.

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