What is the difference between an AR-15 & a M4?
Although they look similar, there must be some technical differences?

Learn me please........

AR15 is basically the civilian version of the military M4.

The original AR15 has a 20" barrel, whereas the civilian AR15 has a standard 16" barrel. The military M4 was originally a 16" barrel and has evolved into shorter barrels for some CQB. The M4 (since its military) also has select fire which is capable of full auto.

All in all the AR15 is the M4 for a civilian.

You can read these articles and better understand a little if you like.

Modern Firearms - M16 M16A1 M16A2 M16A3

Modern Firearms - M4 M4A1

The AR15 is the semi automatic version of the military M16 rifle. The M-4 is a carbine length version of the same rifle, usually seen with a collasible buttstock and a shorter barrel. That's pretty much it in a nutshell, but there are a multitude of different configurations of these rifles.


The full sized AR15/M16 (all variants, A1, A2, etc.) has a 20" barrel. The civilian version of the M4 has a 16" barrel, military versions of the M4 and it's predecessors (CAR15, GAU/GUU, etc.) have a 14" barrel or shorter.

The biggest difference is that the M4 has select fire capability and a 14.5" barrel.

As far as parts, the M4 has one more pin in the fire control mechanism with an arm on it. The BCG has more metal to it. and the Safety Selector has another position on it.

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Grover Oathkeeper

Gunblade's explanation get's my vote except the M4 has a shorter gas tube, different buffer and spring, and specially cut ramps in the barrel and extension so the ammunition feeds better during the more violent operating cycle caused by the higher port pressure of the shorter gas tube.

The M4 is the one i dont have in my gunsafe yet

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part-time ninja...

One is for Fighting One is for Fun.

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THIS WE'LL DEFEND ΜΟΛΩΝ ΛΑΒΕ

The civilian version can also have an upper heavy (bull) barrel or lighter (special order) barrel up to 24". I have a 20" special arder RR light barrel upper. Working on a 24" bull barrel for my next upper when things catch up.

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THIS WE'LL DEFEND ΜΟΛΩΝ ΛΑΒΕ

The one real difference (other than select fire) is that the M4 has an hourglass cut out on the barrel for mounting the M203 grenade launcher.
Those semi auto only ARs that have the same barrel configuration are commonly called M4geries.
Later additions to the M4 included feed ramps that are cut into the upper receiver its self.

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Hold my beer and watch this!

Every army guy here knows EXACTLY what that means....

I never had to do it because my brother joined before I did and I heard his horror stories before I made the mistake. I watched a lot of guys go through the agony because they couldn't figure out they were carrying a weapon.

I remember so clearly the time a new found friend of mine (just issued our weapons in boot camp) raised his hand and asked the DI what we were supposed to do with our gun during chow?

The DI marched over and got right in his face and asked him to repeat the question so ALL of us could clearly hear it!

I cringed as he yelled out "Seargant! The private would like to know what he is to do with his gun at chow Seargant! "

That DI smiled the kind of smile satan himself teaches in DI school, and as he walked back to the front of the platoon, he barked "You men will keep your weapons with you at all times! You will eat with them, you will shower with them, you will sleep with them, they will be your new girlfriend while Jody is home with your old girlfriend!"

Then he yelled, "Private Smith! Front and center!" and the poor dog who asked about his gun ran up front and stood at attention. The DI then explained how private Smith obviously has his mind on the wrong things. His mind was thinking of home, of his girl, and thinking of his gun. To help him remember the difference between a weapon and his gun, the army has a helpful little song he would teach private Smith, and private Smith would skip chow today and practice the song while the rest of us ate. He would continue signing until the last troop was finished and back in formation.

Smith then ran around the outside of the chow hall yelling "This is my weapon!" while holding his rifle over his head with both hands. "This is my gun", and he'd grab his privates with one hand. Then both hands back on the rifle over his head "This is for fighting!" and once more grabbing himself "This is for fun".

It takes a platoon about 15 minutes to eat chow, and he ran around the building the whole time. One guy laughed and got to join him, that kept everyone else's eyes on their plates and wolfing food as fast as possible.

Smith never did learn the lesson and had to sing and run at least 6 times. Once when we were out on a 5 mile run, he had to run around the platoon as we were running down the road. I thought he would die.

Often our sergeant thought it would help if the rest of the platoon were motivated to help Smith remember the difference between a weapon and a gun, by doing push-ups while Smith ran around the platoon singing.

Man we ended up hating Smith....

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Kirk / Spock 2020

I'm pretty sure that Armalite called it the AR15 before the military dubbed it the M16, but would have to look it up.

Here's the difference:

M16A2: 9/3
M4: 6/3

That's right. The original AR15s were made by Armalite and were marked as such but had M16 stamped into the mag well. After Colt got started making the rifle the AR15 marking was dropped, IIRC.

I found a picture in one of the AR books I have around here written by Patrick Sweeney that shows a pre-1963 Colt made, Armalite named, select fire rifle. Looking the picture over is kind of cool. The lower is marked AR15(no M16), cal. 223, model 1. If I can get a decent picture to scan, I'll post it.

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15T,15-22,5946 & some not S&W

Here it is.

Attached Images

colt 001.jpg (94.1 KB, 1153 views)

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15T,15-22,5946 & some not S&W

This might help

M-4 Carbine vs. M-16 - YouTube

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Jorge
- M&P15, 15-22, Shield

My Dad has a Colt and it is stamped AR15A2!

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Grover Oathkeeper

What's that saying, a picture says a 1000 words?

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15T,15-22,5946 & some not S&W

Thanks for all the great info & video's.
Like a photo, a question is worth a thousand words.
Trash