AR15 vs M16: What Are The Most Important Differences? 

From the hands of the IRA on the streets of Belfast to the deadly jungles of the Vietnam War, both the AR15 and M16 have been deadly weapons of war for decades.

Each of them is almost as instantly recognizable and notorious as iconic 20th-century weapons like the Kalashnikov.

But when it comes to the AR15 vs M16, what makes them different? From the overall design to their global reputations, we find out the fascinating answer!

One Is Civilian, And The Other Is Military 

The AR15 was developed in 1956 as a civilian weapon. The Armalite Company wanted a light, gas-powered, variable-fire rifle for the US Military, and the result was the original AR15.

However, the company faced financial difficulties and ended up selling the rights for the AR15 (and other rifles) to Colt. 

The rifle has since become a mainstay of the civilian firearms scene. There are an astonishing 20 million in civilian circulation, and it’s so popular and iconic that it’s often called ‘America’s Rifle’. 

The M16 is also manufactured by Colt and is very similar to the AR15. The rifle debuted in the Vietnam War and, though it got off to a rocky start, has long become a staple of the US Military (along with its derivatives). 

The M16 has seen many iterations over the years. The latest incarnation dates to 1997 and features the ability to mount accessories on the handguard and top rail, making it more customisable than ever.

However, its 20” barrel has become a liability in recent years, given the proliferation of tight urban battlefields. 

Intended Purpose

The two rifles are extremely similar to one another in terms of design and function. However, there is a rather large practical difference between the two. 

The AR15 is a civilian weapon and does not need the same functionality as its military counterpart.

Simply put: there’s no need for full auto on a civilian rifle. Because of this, the AR15 can only switch between single and burst fire. Any attempt to modify the gun to fire at full auto is illegal. 

The M16, on the other hand, is intended for combat situations and has full-auto fire available.

The Lower Parts Kit 

The safety lever, trigger, hammer and disconnector differ between the AR15 and the M16.

The reason for this difference is simple – it facilitates full-auto fire in the case of the latter and disables it for the former.

The Lower Receiver 

The lower receiver in the AR15 has different dimensions from that of the M16. This difference prevents M16 parts from being placed into the AR15, thus facilitating full-auto fire. 

The Bolt 

Because the M16 can be fired in full auto, it has a different pin to its civilian counterpart.

The M16 bolt is heavier and carries extra mass at the back, which aids the user in dealing with recoil when the gun is firing on full auto. 

This is unnecessary for the civilian AR15, as it is not designed to be fired in full auto. The bolt is, therefore, more lightweight and lacks the additional mass that the M16 requires to compensate for recoil. 


The AR15’s reliability is much-vaunted. The gun performs well in tests (despite being a civilian firearm) and performs strongly and consistently even after a repeated fire over several minutes.

It is, however, slightly more accurate than the M16 over long distances. 

The M16, on the other hand, had a very rocky start. Brought into service during the baptism of fire in the Vietnam War, the rifle performed poorly in the humid jungle climate.

It was prone to frequent jams – obviously a massive problem for soldiers engaged with the enemy in the steamy Vietnamese jungles. 

Because of its poor performance in Vietnam, the Department of Defence invested significant funds to ensure that a repeat of America’s defeat did not happen.

These funds righted the ship, and the M16 became a much more reliable weapon. So reliable, in fact, that it remains the most widely used military rifle in the US Armed Forces. 


Despite the similarities between the two guns, there are some major differences between the reputations of the two guns.

One is associated with American military might, precision and reliability, while the other is tainted by its association with mass shooters. 

Without getting into the politics of the situation, it’s a sad fact that the AR15 (or functionally identical ‘AR15-style weapons’) has seen use in some very high-profile mass shootings in the US.

The Sandy Hook Elementary School shooting, the 2017 Las Vegas mass shooting and the recent Uvalde, TX shooting all used AR15-style rifles.

In the case of the Las Vegas shooting, a ‘bump stock’ was used to make the rifle functionally full auto – an illegal modification but not difficult to make. 

Despite their aesthetic and design similarities, there’s no escaping the fact that the two guns cast very different shadows. 


Civilian guns have a close-to-zero chance of seeing a combat situation and are much less used than their military counterparts.

Because of this, they do not need to be quite as durable as military rifles. This means that if consistently used, they’ll wear out faster than a military rifle. 

The M16, on the other hand, needs to be able to be used daily and keep functioning.

This means that it needs to be able to sustain high rates of fire without malfunctions or faulty parts, so things like the gas tube are of a higher quality than the ones found in the AR15. 

On top of this, the M16 has a looser ‘tolerance’ than the AR15. This means that the parts inside an M16 are put together more loosely than those in the AR15.

While this may sound like a bad thing, it’s actually better for military rifles. Why? Because military rifles are in the field and not in a gun rack.

They’re going to get wet, dirty and bloody far more than a civilian rifle. This calls for a looser tolerance, as such a tolerance means that the rifle can keep on firing even with dirt and water getting into it. 

Price and Availability 

Put simply: M16s are not available for civilian purchase. The only way around this is to find one that was made before the 1986 ban on sales to the public.

Such guns are rare and accordingly expensive (expect to pay upwards of 25k).

AR15s, on the other hand, are widely available (again, more than 20 million are in circulation) and relatively cheap. 

AR15 vs M16, a Conclusion

To summarize, there are ten main differences between the AR15 vs M16. The former is a widely available civilian weapon, whereas the latter is a firm weapon of war.

Both weapons serve dramatically different uses in the world of guns. But regarding sustainability, global reputation, and reliability, the M16 beats the AR15 hands down.

RavenCrest Tactical


From Eastern Ukraine to the mountains of Chechnya, Jay has spent the better part of a decade working on the ground as a security consultant in some of the world's most high-risk areas. His work can range from unrivalled insights into breakaway states to covering the latest tech on the defense market and everything in between!


Please enter your comment!
Please enter your name here