M4 VS AR15 [Similarities & Major Differences]

M4 VS AR15, to the naked eye they are the same. But this guide breaks down their differences a bit more including their histories, design tweaks, naming and usage.

M4 VS AR15 Major Differences

On the baseline level, they operate the same. A military M4 barrel is slightly shorter and has the ability to fire in full-auto.

The modern-day “standard” AR-15 that the vast majority of us normal people buy is generally a 16" barrel from tip to tip without the muzzle device, with an adjustable stock while the M4A1 has a 14.5" barrel.

In another word, we can just say military AR and civilian AR.

The major defining difference between a military AR15 and a civilian AR15 is the select-fire capability. While all of these rifles have “safe” and “fire”, only military AR15s have 3-round burst and/or full-auto. There is a very small number of AR-15s/M16s that were made in full-auto before the 1986 ban, but those are insanely rare and cost about $30,000+ plus a bunch of NFA paper required to get one.

What Does The Letter "M" Stands For

M4, M16, M - whatever. It tends to throw people off when researching about this weapon platform. 

It's simple - M stands for "Model". It's what the military likes for naming things. Each type of weapon is considered a different line of naming. So, rifles are rifles, carbines are carbines, and the same goes for pistols and SMGs. They all get an M+number, but they are numbered as separate things.

Brief History Of AR-15


The story of the AR-15 begins with the AR-10. AR stands for ArmaLite (Not "Assault Rifle", typical wrong association in the English language). George Sullivan founded ArmaLite in Hollywood, California, as a division of Fairchild Aircraft Corporation. Eugene Stoner joined the company as the lead engineer shortly after.

This guy is the engineering mind behind this amazing rifle system. The AR10 design came first, then AR15 was born.

The AR-10 was a revolutionary design, primarily using plastic and aluminum, and weighed only 6.85 lbs unloaded. However, it didn't fare well in military testing due to a barrel failure.

Despite this setback, ArmaLite didn't give up. They sold the rights to the AR-15 design and name to Colt in 1959. Colt then released the Colt 601, the first AR-15 design rifle to hit the market.

Brief History Of M4

Almost as soon as the AR-15/Colt 601/M16 made it into the field, there was a need for a shorter version of the weapon. Colt's solution was to cut 5" off the barrel and name it the Model 605B CAR-15.

Model 605B CAR-15

Colt continued to work on a smaller version of the AR-15/M16 well into the 1980s. In the early '80s, the US Marine Corps asked Colt to upgrade the M16A1 with a number of changes, resulting in the M16A2.

The US Army asked Colt to develop their own version in 1984. Testing started immediately with experimentation carbines named "XM4" finding their way into the hands of special forces within a year. It took 10 years before it was adopted as the M4 in 1994.

Military M4 VS Civilian AR15 - Which Is Better ?

In the context of comparing a military M4 without leadership's approval to upgrade, and a civilian AR15 with high end accessories.

The short answer is that a modern civilian AR15 is way better than a standard military M4 for many reasons:

A standard military M4 has to follow military official guideline MIL-R-63997 to qualify to be in service, and it's not a personal item to just randomly customize.

Credit RecoilWeb

It features bare minimum features to operate including that 8 pound trigger pull. The full auto trigger system is a plus, but it's only designed for fire suppression, not for precision shooting.

Conventional military units prohibit service members from upgrading their issued weapons without leadership's approval. Since service members aren't paying for any of it, they get whatever the military has.

A typical military issue M4 comes with basic quad handguard, bipod, Aimpoint or ACOG.

This is not to say that a standard issue M4 can't be as good as a civilian AR15. In a dream world, where you can add whatever upgrades to a M4, then it will be just as good.

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