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Understanding the Different Types of AR 15 Rifles – M4 vs. M16 vs. AR15 – A1, A2, A3, or A4

M4 vs M16 – M16 vs AR15: What Are Their Differences?

The AR15 platform has undergone many changes over the years, and it can be pretty confusing to the average gun-owner. The goal of this article is to help you keep it all straight.

M16 Brimob Grande

AR15 vs. M16 vs. M4 – What’s the Difference?

To understand the different types of AR15’s, you first need to start with a little history.

The AR-15 was a direct evolution of the AR-10, which was developed by Eugene Stoner in the 50’s. The first ones were no more than simple scaled down versions of the AR-10.

In the late 1960’s, the US military began use of an AR-15 variant known as the M16 rifle. This rifle became standard equipment for the US Army beginning in the Vietnam War. The rifle has gone through several generations of improvements since the original model – we will explore these later in this article.

In the 1980’s, Colt began work on a new platform based on the M16 rifle, which was eventually known as the M4 Carbine. The M4, which features a shorter barrel, collapsible stock, and other modifications, has become standard equipment for close-quarters combat through the US Military.


Trying to figure out how AR 15 Barrels work? Check out AR-15 Barrels – Intro, Fundamentals, and Manufacturing of AR-15 Barrels


While the military still uses the M16 for some infantry applications, it is being phased out in favor of the M4, as the M4 offers distinct advantages in portability and maneuverability through its lighter weight and smaller dimensions.

Do you need a Sling for your M16/M4/AR-15? Read this.


Don’t miss it... Sign up to get US Army Service Manual for AR-15!


A1, A2, A3 and A4 Similarities and Differences

AR 15 Variants - A1, A2, A3 and A4 Similarities and Differences

You’ll often hear people refer to the different types of AR15’s as A1, A2, A3, or A4. These terms actually refer to the different generations of the M16 rifle, and they are often used incorrectly when referring to AR15’s.So what are the differences between these different types of M16’s?

The carry handle is a big difference between models and is a good place to start off from.

The A1, A2, and A3 have a permanently-attached carry handle and the A4 does not. Although the A4 has a removable carry handle option, it does not look anything like the previous versions. The A1 carry handle also featured the rear sight which had a tool-adjusted windage selector (a bullet tip could also be used to make the adjustments, and that’s what most soldiers would do).

One feature that is similar to all these models is the forward assist. It is a standard feature and is equipped in all the 4 types – A1, A2, A3, and A4. The forward assist was non-existent to the original incarnation of the M16 but is a necessary option to make sure that the bolt is fully forward and locked.

The A2 and A3 went further on the idea and incorporated easy adjust windage and elevation selectors on their carry handle rear sight. These are all nonexistent features in the A4 with the carry handle having been removed from its design.

The A2 design featured several improvements over the A1, including a spent case deflector immediately behind the ejection port to prevent cases from striking left-handed users, a heavier barrel, and the modified action that replaced the fully automatic setting with a three-round burst setting.

The A3 is so similar to the A2 that they are almost twins. The main difference between them is the fire-select feature on the A3, other than that they are the same weapon.

The A4 may be referred to as the flat top version because of the removal of the carry handle and it distinguishes itself as the only one in the group ready to be equipped with an optic. Very much unlike the A1, A2 or A3 which require an adapter to fit on optic on top of the handle.

To summarize, much has changed through the years, and the US Military has driven many improvements on the original AR 15 platform. While all of these different changes can get a little confusing, the result has been improved weapons for both military and civilian use.

Looking to build your first AR 15 or would love to upgrade? It’s easy and affordable with AT3 Tactical’s AR 15 Parts and Accessories!

One Last Tip

If there’s anyone that knows the AR-15 platform, it’s the US military. As a special offer for our readers, you can get the Official US Army Manual for AR-15/M4/M16 right now – for free. Click here to snag a copy.

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58 thoughts on “Understanding the Different Types of AR 15 Rifles – M4 vs. M16 vs. AR15 – A1, A2, A3, or A4

  1. I believe the M4 has had the feed ramps re-configured to make feeding more positive. I have an AR15 A2 that I bought in 1980 about 12 years after returning from Viet Nam. I also have an M4. You can’t tell the difference by looking but take them both to the range and you can see the difference. If you run the A2 wet it functions well but the M4 runs wet, dry, or full of dirt and it will usually function. I built the M4 myself and I made sure all the tolerances were correct.

  2. Point of clarification: the M4 absolutely did have a carry handle that came with the weapon. As correctly stated in paragraph 8, it was a removable carry handle that fit onto rail system. It was very similar in appearance to the A2 and A3 carry handle, though I believe the adjustments were finer. Finally, the A4 include the Knight’s Armaments rail system that allowed one of four panels to be field removable so that you could attach accessories. Also, the twist in the barrel was taken from the 1/12 considered optimal for the US M193 5.56mm cartridge to the 1/7 twist for NATO SS109 standard cartridges. There were also a LOT of changes to manufacturing methods that helped with reliability and operation in the field.

    Would have loved to have included some mention of the CAR-15. The dramatic changes from the M16A2 to the M4A1 seen in pictures above are largely due to the militarized version of the CAR-15, designated the GUU-5P. The Army Special Operations community was still using these into the mid 1990’s, and they were employed by Delta Force (technically “Operational Detachment Delta”) operators during the Battle of Mogadishu.

  3. I believe it’s worth noting that the term AR10 and AR15 meant Armalite Rifles, models 10 and 15. AR was not short for Assault Rifle — that was a term introduced years later in liberal political circles. See if interested.

    1. Daniel Rimmer, He actually stated it this way :
      “was a term introduced years later in liberal political circles.”

      Never said :
      “Liberals” invented the term assault rifle.

      However, the point is well understood; “Liberals” do regularly use the term
      for purely political reasons !!

  4. cool

  5. @Joel Reisner – please leave the politics at the door or at least get your facts straight. “Liberals” did not invent the term assault rifle. Its a translation of a the German word “Sturmgewehr” as applied to the Sturmgewehr 44; generally recognized as the first modern assault rifle.

    1. Joel Reisner was referring to the AR-15 being erroneously called an assault rifle! He was NOT referring to the origin of the term assault rifle which was adopted from the Germans in WWII.

    2. Correct and thank you for making that point. Some of us “liberals” build and love our guns too. Even 3d print or mill out our very own ghost guns, lumping all people of liberal mind sets into a monoblock of homogenous politics is not accurate or fair.

      1. Thank you for bringing this up. I am what many people in the gun world would call a liberal if I were not talking about or holding my gun. Democrats and moderates own guns and support the second amendment. Call all Democrats liberals is like saying all republicans are racists!!! It’s all just not true. Every individual is different and has different thoughts and political opinions. Lumping everyone into liberal and conservative is just, in my opinion, wrong and ignorant.

        1. Amen, I vote blue, well because I don’t care for Fascism in American Democracy. Anybody support that supported America during WWII, spoiler, you’re Anti-Facist. Also it’s a FREE COUNTRY. Not Red or Blue. You can actually have a little bit of both ideologies, and believe it or not. Your head will not implode from open mindedness.

          1. Anybody that Supported*

          2. How can you say you don’t care for fascism yet you vote for the people who want to remove your ability to protect yourself from fascism and who literally are fascists?

        2. Being as the democrat party owns the legacy of slavery, segregation, Jim Crow, lynching, Eugenics, the KKK, Gun Control and other race based atrocities it would take a history illiterate to assume they have a podium to call The Party of Lincoln, “racist.”

          1. Thank you for pointing out the hypocrisy of the Dem party, they are always so quick to conceal their origins

        3. Haha… How about now? Are you still Democrat? Are you going to wait until they bang your doors down and take your guns to realize who they really are? Its True many good people Still think they are Democrat simply because they believe the Lies and utter Hypocracy of this Communist Regime who pretends to be everybodys friends..

    3. Guess it’s a good thing that he didn’t say that, you boomer moron. But please, do tell me about how the NRA is the pinnacle of our 2nd ammendment

    4. Guess it’s a good thing that he didn’t say that, Elmer Fudd. But please, do tell me about how the NRA is the pinnacle of our 2nd ammendment

    5. Everything about guns is political today, and with very few exceptions, only one party is making waves. So it’s worth reminding others of that fact as November approaches.

  6. The term “assault rifle” was first used to identify the StG 44. The term invented by liberals to scare the uninformed is “assault weapon” which is really meaningless. Assault is an action. Using their “logic” a Swingline 747 stapler would be an “assault stapler” when someone used it attack someone.

    1. Words mean things: As TDS has evolved over the last 3 years, we need to distinguish between the classic Liberal and today’s Leftist – folks demonizing “assault weapons” and “assault rifles” in 2020 are properly termed Leftists or Leftistas.

  7. It would be a lot more helpful if the picture of the rifles were in respective order of a1, a2, a3, & a4…..or there was an explanation of model order. It goes a1, a2, a4, a3?

  8. Dumb dumb, He did not infer liberals created it. You created that from nothing. Ignorant or not knowing people tied AR to assault rifle because in their ignorance they thought ar acronym refered to assault rifle. Analogy or not, It became alive. Armalite Rifle is dead in ref. to ar, and anything resembling it is scary.

  9. The forward assist is not necessary and Stoner never wanted it. If you have to use your forward assist then something is wrong with your rifle and jamming a cartridge in the chamber is not the proper thing to do! There is a reason the SR-25 doesn’t have a forward assist. The only reason we have the forward assist is because of public demand. Have any of you ever used it? No, didin’t think so.

    1. I have. I had to use it a few times while training in Ft. Bliss back in the 70s. Keeping the sand out of my rifle was near impossible while crawling on my belly.

    2. Shut up dick weed in a fire fight your not going to be analyzing all the aspects of the ammo or the weapon ! save up for a brain !!!

    3. Absolutely correct Mark. All the forward assist does is assist you in making a jammed round even more difficult to extract by pushing it farther into the chamber. Not a fan.

    4. The forward assist was added after the US Military experience with jammed M16s in Vietnam. The original M16 had no forward assist and Jammed frequently from the sand and dirt under foxhole fighting conditions.
      The original also had a brittle stock that our Drill Sergeant warned us was made by the Matel toy company and it would shatter if one fell on it too hard when grabbing earth. The M16 was extremely unpopular among soldiers in Vietnam for those and several other reasons.
      We were issued those little comic books that reinforced the need to constantly clean the weapon in the field.
      That’s why the forward assist was added.

      1. Sonny, the assist was not as necessary, when they changed from the black bolt 2 the new Crome bolt. The black bolt collected burnt powder residue, also dirt & crud ( mud, sand, bark, grass, etc.). Crome bolt finish was smooth, didn’t accumulate as much dirt. When needed it was a God send, open bolt u r SOL! Clean rifle is very necessary 4 proper cycling, & function. I used both, assist was a life changer when needed, like “toilet paper”.

    5. I built my very first AR sitting in my living room. The first time I went to fire it, the bolt did not quite push the cartridge into battery. I gave it a loving nudge with the FA, and it locked right in.

      Since then, I’ve never had to use the FA on that weapon or any of the several I’ve built since. I have seen people suggest using the FA to “ease a round home” when trying to stay quiet, so the clacking of the action doesn’t alert a bad guy to your presence or intentions.

      When seconds count, I’d prefer to be able to bang something into position and fire off a round, even if there’s a problem and it’s the last round that weapon will ever fire.

  10. Mark is correct about forward assist is not necessary. When M16 was put in service during the Vietnam war, the ammo (powder used) provided had very low quality and it created so much dirt inside the receiver which causes the M16 to jam frequently. The purpose of the forward assist is to jam the BCG into proper battery position. Today’s ammo is much more cleaner and burns much better. As a result, the forward assist is not necessary or required in an AR rifle flatform in todays modern AR.

    1. I shoot in the desert. Without a forward assist blowing sand and dirt create the need for the forward assist, as in Vietnam when in foxholes. I’ve shot a lot of Vietnam era 5.56 on the range and never had a problem with dirty powder. Dirt and sand in the boot is why the dust cover was added. I still carry a big bottle of LSA in the field.
      I’ve seen a lot of expensive AR platforms jam or go down with failures owing to dirt in the upper.

  11. I’ve read elsewhere the forward assist was used to silently charge the bolt.

    1. Yes. It worked for me once 51 years ago. Sometimes you had to be real quiet.

    2. I was 10 years old during the war, hated marxists almost as much as I do now, prayed for our guys while my mom cried at the kitchen table over letters home. I followed it all carefully. It was my life. I fought liberal POS kids after school standing up for our guys over there. Most libs were pussies, and they’re still pussies. I remember the “new” forward bolt assist very well. I defer to the guys that were there, but I remember our guys hating “the little black gun” as the VC and NVA called it. It was getting guys killed. So when they added the forward assist, it was a big thing. I remember when our guys needed it, they needed it, and they used it. Each knew the consequences as each knew his weapon. As far as quietly closing the bolt, I’ve never heard historical evidence of that. When they needed the FBA, I remember noise being the least of their worries unless they were GB’s. Ive always pressed my thumb hard into the indent on the bolt for better control closing it quietly. If I used the FBA at the same time, it didnt end well—applied more force than necessary—and the buffer spring slammed it home Ka’ching! But if you were there and you say you did, defer to you. As far as democrats and guns, I honestly have never understood that one. We’ve all seen the success of Marxist incrementalism over the last 60 years finally bring marxism into the WH today. If you voted democrat in the past (before 2008), you just voted democrat. If you vote D today, you are voting for marxism. Do not fool yourselves. Because 1. none of the dem politicians have the balls to stand against it, or 2. they really believe that bull sh*t. I’m 61 now, and I’ve seen Marxist Incrementalist creep in the disguise of “simple liberal politics” for over 50 years. I remember “oh, that’s so stupid to believe giving a liberal inch will result in a Marxist mile.” But it does, doesn’t it? Look at the WH now. A demented commie puppet and his commie whore side kick living as head of the free world and cramming CRT down our soldiers throats. For whoever said “not all republicans are racist” —f*ck you, *ss hole. That assumes some R’s are. And f*ck you up the *ss for saying that. Yes, MF, I’ll meet you anywhere, just like I did 50 years ago—you f*cking marxist *ss lick. I hate ya all. Go patriots. See ya at your revolution libs. You’ll take the Marxists side—you already have. You like guns and you vote democrat? What are you? F*cking stupid? That’s a rhetorical question. Of course you are..

      1. Thank you for pointing out that the Dems are historically, factually, the documented party of racism. Always the first to conceal their origins and accuse others of what they do.

  12. So I just recently bought a dt sport lite 556.. what do I have to do so switch it to the the 1-8 m4 barrel .. just looking for help someone message me

  13. In the photo of the 4 firearms, it appears that number 3 from the top is an SBR (Short Barreled Rifle) in relation to the other three firearms. Someone (Non-Military or non-LEO) owns that one without proper interaction with the ATF and paying tax stamp in in trouble. Then when you get right down to it, the other three are actually carbines, just to be picky. Has anyone but myself noted that any carbine length barrelled firearms seem to lose their effectiveness and accuracy right about 200 yds and beyond?

    1. The M16 millitary variant M4 issue rifle used by the millitary uses a 14.5 inch barrel and it’s civialian AR15 counterpart uses a 16 inch barrel.

    2. WRONG, the 3rd rifle is legal.. its a pistol.. barrel shorter than 16 inches, and has the paddle/fin style stock with the strap inserted which allows for single handed firing… EDUCATE YOURSELF PLEASE!

      1. And where is the paddle/fin stock? Behind the retractable one? Stop insulting people because sometimes you make a ass out of yourself.

      2. Sorry Ron you’re wrong the third rifle is an SBR you’re wrong about the stock that is not a paddle and with the vertical front grip you have to apply for a tax stamp please educate yourself about the pistol version where you’re not allowed to have a front grip in that configuration which turns it into an SBR small Barrel rifle and it requires a tax stamp

      3. Wrong yourself. That is a collapsible stock on a short barreled rifle. License required for civilian use, not the military, Also the vertical fore grip is prohibited on a pistol. A pistol is defined as designed for one handed operation.

      4. The 3rd rifle has a stock and not a fin, blade or anything else you want to call it! Put your glasses on and look glasses 🤓 All 4 have legitimate stocks.

      5. You need to take your own advice. A legal pistol is not allowed to have a vertical grip. So, if it’s not a legal SBR, it’s illegal.

        1. I could be wrong but the shortest barrel I see looks like 16″ with a carbine length gas system, I believe the other three are 18″ or 20″ with rifle length gas systems. I do believe all these firearms are legal.

    3. The M16 was an open sighted carbine and the qualification range far targets were various ranges out to 300 meters at pop ups. It was designed as a weapon of war that was simple for soldiers to learn and repair to some degree in the field if necessary, and I agree the accuracy falls off, but made up for by the rapid fire nature of the weapon. I’ve built heavy barreled 5.56 AR rifles that performed outstandingly. But If I’m shooting long range for accuracy I’ll take a 7.62 bolt action any day.
      I know you are talking about AR15’s but they are basically all the same animals. I used to teach small arms readiness training for the US Army and run the range.

  14. Ok, serious question… Which of these weapons mimics a machine style? I am interested in facts only, not the where, when, and who came up with names.
    Thank you 🙂

  15. Ok, serious question… Which of these weapons mimics a machine gun style? I am interested in facts only, not the where, when, and who came up with names.
    Thank you 🙂

  16. What is all this political crap? I’m just trying to find out if I can use an M16A2 trigger in an AR15 lower??

    1. The atf says “once a machine gun always a machine gun”. The fire group can always be called into question in court. However if it’s just a trigger no serial no question. It’s your choice is a m16 trigger worth life in prison? If it were me and I needed parts I would throw it in and never look back

  17. American Rifle is what AR stands for now days

  18. Hi Folks, I saw a sign the other day, It’s damn funny! “If Guns Kill People, Cars Drive Drunk, and Spoons Make People Fat” I laughed for a long time!

  19. I have an AR that says on the lower receiver 5.56 M4 Carbine and is from Aero Precision. It has a 20 inch barrel which I do not understand. I thought the word Carbine meant a shorter barrel. The rifle did not have a carry handle, I bought one from Palmetto State and added it.. I called Aero Precision and they said that someone probably used an Aero Precision lower and put on a 20 inch barrel for the upper. Does anyone have any thoughts on this?.
    Thank you.


    1. Carbine gas tube? Hell I don’t know. A collapsible stock used to to be the mark of a carbine in the early CAR days. Back then, we thought we needed a 20” barrel for velocity and accuracy. I owned a CAR before the kayak accident.

  20. Old post but a small correction. In regards to the forward assist, the USAF M16s prior to the adoption of the A2 in the 90s didn’t have a forward assist or a shell deflector. To confirm this just Google USAF M16 604.

  21. Enjoyed this article..and the manual. Manual has lot’s of details.

  22. Thanks for sharing this awesome blog with us.

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