Find Out What Barrel Length is Best for Your AR

With so many barrel length options, which one is the best for new shooters?

The AR-15 is America’s rifle, at least for the moment. Everyone should own two. We have been using 5.56/.223 in this gun for over 40 years and like it or not it is combat tested as the day is long. One of the top questions I get when people go to buy their first AR is, “What barrel length should I get?” Fear not dear readers, for I have an opinion on this. And right after, I will give you the details on a foolproof Middle East success strategy.

If you shop hard enough, you can find barrel length options from 7 inches all the way to 36 inches, which is pretty insane. For the purpose of our new buyers though, it is pretty safe to talk only about the 11-inch up to 20-inch versions. They are the most common.

Just like your mom, I am not a fan of short barrels. The big drawback to shorties is the loss of velocity, which I have elaborated on in a previous video. In a nutshell, every inch of barrel you cut off, up to the optimal length that is generally considered to be 24 inches, you lose pressure and have incomplete powder burn. This means your bullet leaves the barrel with less speed and as it bleeds off speed during flight it rapidly enters the zone of “sub optimal terminal effect.” That means it won’t kill something worth a damn. And whomever you shot will be mad at you, in addition to probably taking it personally. However, that aside, any barrel under 16 inches is governed by special ATF rules. Putting a short barrel on an upper receiver not registered as an SBR is illegal. It’s dumb, but them’s the rules.

What if you really want a MIL-SPEC 14.5-inch barrel? That’s what all the ninjas use, it must be the heat right? Well, no not really. How the DoD decided on 14.5-inches, I have no idea. But they did. If you insist on a 14.5-inch barrel, you can actually still have it with no special tax stamps and government permission slips. The trade off is, it has to have a flash hider that makes it 16 inches overall, and that flash hider must be permanently attached. This is commonly referred to as “being pinned and welded.”

A gunsmith actually drills a hole through the flash hider and into the barrel, inserts a pin, and then welds the hole shut. For all practical purposes, it’s not coming off after that, ever. You can cut it off, but then you have a 13.5-inch barrel. And for the labor for removing it properly, you could buy a new barrel. So what exactly is the problem? No room for growth. You might be happy with this exact setup today, but you won’t always be. Suppressors? You are going to need a new barrel unless you bought the flash hider specific to the brand of suppressor your future self wants. Competition muzzle brake instead of flash hider? New barrel. New gas block and handguard? More than likely, new barrel. To me, this argument alone puts anything below 16 inches out of the equation.

SEE ALSO: Gunfight Science: SBRs in 5.56 Suck – Buy a .300 BLK

So that leaves us 16-, 18-, and 20-inch barrels. Twenty-inch barrels are becoming less and less common, with some exceptions like the FNH M16A4 copies on the market right now. Nothing wrong with a 20-inch; it will give you some more punch in the velocity department. All of us former Jarheads have carried them around a bunch. They work fine. My only complaint about a 20-inch is that they don’t feel as balanced in your hands.  Plus that extra 2 inches over the 18 creates some silly limitations. My truck door won’t close with a 20-inch under the seat. It’s harder to conceal them in a backpack or other carry bag. There are fewer case options. And not that I am a slave to fashion, but a 20-inch looks retarded with a collapsible stock on it.

The top is the Barnes Precision Machine government-profile barrel.  On the bottom is the Larue Tactical pencil barrel.

Now we’re down to the 16 and 18. The 18-inch will shoot a bullet faster but at a cost of added weight and size. The real question is, how much faster? I was kind of surprised by the answer to this. The 55 grain was the lightest bullet I tested, and probably the most common round available. In my two guns, there was only a difference of 110 feet per second between the 16-inch and the 18-inch. With 69 grain ammo, the difference was down to 75 feet per second. That doesn’t make a lot of difference in bullet drop at range. I can understand why a light sniper rifle would go with the full 18-inch barrel, to squeeze every ounce of velocity and reach out of the gun. But for a general purpose rifle, that isn’t enough for me to renounce the 16-inch.

How about barrel profile? Does the thickness of the barrel really matter? Usually, it does. The thickness of your barrel generally increases rigidity, which directly affects how well your gun shoots. There are many other factors, not least of which is how it was cut, but all other things being equal, a more rigid barrel shoots tighter groups. The thickness of the barrel also dictates how long it takes the barrel to heat up, which generally also decreases accuracy until that barrel cools back down. A thin barrel heats up faster, and a thick barrel takes longer to cool off.

You’ll note the difference in thickness between the Barnes Precision Machine, on the right, and the Larue Tactical, on the left.

For my accuracy testing on this one, I used two Barnes Precision Machine government profile barrels, a 16-inch and an 18-inch, and an 18-inch Larue Tactical pencil barrel. Larue makes a helluva gun, it just happens to be the only one I have that has a thin, pencil barrel on it. It was certainly on the expensive side, and that pencil barrel shot just over a 1-inch group at 100 meters. For a thin barrel, that is actually pretty amazing. My Barnes Precision uppers are both a government profile, which is on the thicker side. They both, the 16-inch and 18-inch, shot a little over a ½ inch.

What does this shake out to? My advice for the new AR-15 shooter is to go with a 16-inch government-profile (or thicker) barrel. The accuracy advantage will keep that gun relevant for a long time and 16 inches is manageable in any situation. If I was going to combat today anywhere besides the flattest of deserts, a 16-inch barrel would be my choice. It balances well, stashes in the car if you need that, and is infinitely doable for CQB. It is accurate enough to do most jobs inside 800 meters and carries enough velocity to make urban combat ranges lethal. It is a pretty hard balance to beat. I like thin profile guns for games like 3 Gun, and I have carried a short barrel when I also had a .308 on my back to do any real work. But pound for pound, the 16-inch barrel in 5.56 is pretty hard to beat.

To purchase a Barnes Precision Machine barrel, click here.

To purchase a Larue Tactical barrel, click here.

About the author: Clay Martin is a former Marine and Green Beret, retiring out of 3rd Special Forces Group. He is a multi-decade and -service sniper, as well as 3-Gun competitor and Master ranked shooter in USPSA Production. In addition to writing about guns, he is the author of “Last Son of The War God,” a novel about shooting people that deserve it. You can also follow him on twitter, @offthe_res or his website,

{ 37 comments… add one }
  • Joe January 26, 2018, 8:06 pm

    The main reason the m4 had a 14.5″ barrel was to make it be the same length as the 10″ barreled car-15 colt commando (often equiped with a 4″ flash suppressor). Gave it better ballistics in same length

  • Scotty Gunn July 22, 2017, 4:59 pm

    I like stainless fluted 18″ barrels 1×8 223 Wylde. I ceracote them black to kill the glare. I have shot them out to 500, and they tend to do quite well.
    You are allowed to marry a less than 16″ barrel to an upper, provided it is for a pistol.
    A blind pin is a hardened pin, no one hardly ever welds over them, except perhaps a factory gun. Most people can do this at home, saving a trip to the ‘smith.
    There are places that sell barrels just as good as the links he provided, but for much less.

  • Jim July 22, 2017, 11:10 am

    I have changed several pin and welded muzzle devices on 14.5 inch barrels. Any competent gun smith can do it.

  • Russ H. July 21, 2017, 3:02 pm

    Go to a gun store or ask here, everyone is an expert. At least some asked some good questions. I can\’t help but laugh at people on the range with every contraption ever made hanging on their AR (especially IR stuff) – guys with $5000 guns and equipment and suppressors shooting Wolf ammo at a target 5 feet away. They always seem to have \”operator beards\” too yet have never been in the military. Funny! Good article, think think some folks learned something here.

  • William July 21, 2017, 12:54 pm

    5.56? .223? My question is why? All .22 Caliber weapons are varmint guns, at best! It’s against the law to shoot deer sise game with a 5.56/.223 in Colorado! The Colorado Game and Fish know what they are doing with this law! Far to many deer sized game are wounded, and left to die. The average deer is under 200 pounds, as are humans. The .22 Cal.barrel is toast after 750 rounds. The U.S. Military made a bad choice with the .223 and didn’t realize it until Kuwait, Iraq, Afghanistan. In the wide open spaces the .5.56/.223 was useless!
    Thirty Caliber weapons are a far better choice.

    • Dave July 21, 2017, 1:40 pm

      More states allow the .223 than ban it for dear. So could be Colorado is wrong.

    • kb31416 July 21, 2017, 3:36 pm

      William, 30 cal is great, but I must challenge two points.
      1. My AR15 service rifle that I compete with at Camp Perry generally has a competition grade barrel life of 4-5000 rounds, which means that it is still holding about 1/2 MOA. At some time around the 4-5000 round mark, it will suddenly stop holding the 10 ring at 200 yards, then it is time to re-barrel. I get lots more than 750 rounds, so unless I decided to rapidly dump 20-30 full magazines as fast as I can shoot them, I do not expect to burn out the barrel.
      2. There are countless heroes of the revolution and martyrs for allah that give mute testimony to the effectiveness of the 5.56 cartridge fired from an M16. Not all bullets are equal, and the 5.56 can be loaded with much better projectiles than 55 gr FMJ or SS-109. 77 grain OTM in the M262-Mod 1 will reliably slay 2 legged enemies out to 600+ yards, and 68 grain soft points are available for hunting that will kill deer if shot in a reasonable location.

  • Zupglick July 21, 2017, 12:50 pm

    Anything less than .30 cal. is a BARBIE gun. Takes at least twice as many rounds, on average, to make target lie down and be good. I would rather shoot once and move before target can zero in.

  • Rick July 21, 2017, 11:47 am

    “And not that I am a slave to fashion, but a 20-inch looks retarded with a collapsible stock on it.”
    Actually, that marks you as somebody who is indeed a slave to fashion. Possibly a retarded one at that.
    Numerous militaries are using exactly that configuration, including the Canadians on our northern border. Didn’t hear them over in A’Stan with us, bemoaning the appearance of their rifles. Also didn’t hear much pissing and moaning from them about the ineffectiveness of standard NATO ammunition – I wonder if having the extra velocity from the extra 4″ of barrel helped?

    Looking at a military rifle with an eye to fashion while attaching front pistol grips, laser designators, lights, etc is kind of bemusing. Any M16 variant set up for battle looks more like a Lego project than some elegant firearm like a hunting rifle with deep blueing and a finely checkered walnut stock. That is the beauty of the platform – their modularity and placement options for accessories.

    Of course, for the fashion fairies, the sky is indeed the limit. You can not only choose barrel length for looks, but all kinds of cool colors – Venders Row at Camp Perry had some examples of robin’s egg blue upper receivers for sale. You can put a DMR style butt with all kinds of cool rotating wheels and sliding parts on a 16″ barrelled rifle with pink handguards and a red dot sight in fashionable zombie green. Have your upper and lower anodized to the cool color of your choice, and you will be THE fab fashion fairy on the range.

    There’s a difference between an AR/M16 set up for battle, and one set up with an eye towards fashion and the Looking Cool Factor. Battle rifles are tools where looks are not a consideration; the considerations for a recreational rifle are whatever the owner/builder wants them to be.

    And if you’re only going to poke holes in paper, clang steel, or defend yourself at home owner distances, whatever barrel length makes your heart palpitate will work just fine. An optical sight doesn’t care how long your barrel is.

    • Russ H. July 21, 2017, 3:06 pm

      LOL! Well said! Fashionable AR\’s…

  • Chris Baker July 21, 2017, 11:23 am

    Yes I’m making a second comment based on the other commenters. You all talk like your way more rich than I am. I might be able to afford ONE if I sell a car or don’t do anything else for a couple of months. The way I interpreted the article was which would be best if you could only have one. Each and every one to their own toys is great. It allows you to have as many as you can afford and talk your spouse into allowing. I don’t have the skill or knowledge to build one up from an 80% although I’d relish having one the government didn’t know existed, I’ve always felt that considering the wording of the second amendment it’s none of the government’s business if I own a gun or not or 20. NONE OF THEIR BUSINESS!!! I just kind of wish I could afford one though. Right now I’m waiting for next payday to buy an antenna so I can finally get my HF rig on the air. HAM License KK6LOP. If anyone wants to look me up and walk me through building an 80% lower for my own AR I would love to hear from them. I’d put off buying that antenna to buy the lower kit.

    • Russ H. July 21, 2017, 5:08 pm

      Chris, building an AR from an 80% lower requires some skill, knowledge and specialized tools. If you would be willing to at least buy a lower via an FFL dealer you could build one at you leisure. Or buy a used one from someone without the FFL. The rest isn\’t restricted. Lower – $50-60, Upper – $40-50 w/parts kit, lower parts kit – $40, receiver extension, back plate, castle nut, stock – $60-80, barrel – $130 (you can get a great Ballistic Advantage 16\” for $130 or less), handguard/barrel nut, gas tube/pin – $50-80, BCG – $80. Magazine – $10. Sights are dependent on what kind of upper you use. A decent completed upper from PSA could be as low as $200. The book \”The Competitive Builders Guide\” by Glen Zedicker will walk you through it (there\’s other books if you prefer but Glen walks you right through it). So for roughly $350 to $1000 plus a few tools and you could build a custom AR to your liking, bit by bit in your spare time and it\’s not as hard as you think. Less if you buy used or cheaper parts (not recommended). Or buy a completed upper and a lower. These days if you\’re willing to shell out $400 through an FFL you can buy a whole AR (or a used one without the FFL). You would need some basic tools – a punch, vise, barrel wrench, etc. I\’ve built every one of my AR\’s from scratch (eight) plus an AR10 (308) but I\’ve invested in a lot of tools, which makes the job so much easier – I also spent a little more on parts (a lot more in some cases). Regardless, I\’ll put several of them against any Colt, Daniel Defense or Noveske for reliability and accuracy. The AR is a military grade rifle and made for punishment – I have to wonder why anyone would spend $2500-3000 for one – I\’d rather have a nice Weatherby bolt action for that kind of money. My two cents.

  • Chris Baker July 21, 2017, 10:54 am

    Opinions are like certain anatomical features… Everyone has one. Mine is different than yours which is different from his over there or her’s down the street. Personally I like a heavier gun, I’m a recoil wimp. I’d choose a 22 or 24″ barrel for my gun. it would have a heavy profile as well. I notice you didn’t mention twist rates. Getting a faster twist rate would allow heavier bullets to be stabilized properly whereas a slower twist rate would be better for lighter bullets. I’d probably go with 1:9 for heavier bullets although it’s been a long time since I looked into this and have forgotten most of what I knew. What’s the latest? Does anyone make a barrel for the AR platform that has octagonal rifling rather than grooves and lands? Has anyone even tried it?

    • Mark N. July 23, 2017, 3:11 am

      1:7 was (and probably still is) hot for the heavy rounds, but most seem to have settled on 1:8 as giving all around performance with different bullet weights. 1:9 has been pretty much relegated to the 55 grain to 62 grain bullets (or lighter).

  • Douglas Riding July 21, 2017, 9:57 am

    I can appreciate a man ( meaning person of course ) wanting to own a bunch of these ‘lil toys’… I own 7 myself ! But – living here in Southern Utah, I have observed an interesting phenomenon… Some guys down here collect wives like I collect guns !
    You’d think they’d have a variety – one for every purpose – but NO ! Get in the grocery store line, and you’ll soon realize that all 3, 4 or even 5 could be sisters ! ( Wait – maybe they are !?!??? ) A
    nyway, if it was me, I’d have a blonde, a brunette, and a ‘fast’ redhead… You know, one for every purpose !
    So, maybe you ought to consider limiting your AR’s to a couple, and buying a Garand, or a Winchester..
    I like my Hawken – A LOT !!!

  • Randy July 21, 2017, 8:52 am

    You failed to mention gas ports which is a big consideration when choosing a barrel for 3 gun and other shooting competitions. I don’t see why anyone would purchase an AR for going into combat today like you mentioned. I am not sure you can take your own guns to other countries and use them in our military. The only combat would be if you are law enforcement and allowed to carry your own gun, or you want it for home defense. It all depends on your application on what you want the gun for. I never understand why I see some of the tactical guys teaching classes with IR lasers and other stuff on their guns, like they are going to call in an airstrike or something. Unless they are still in the military and plan on going back to war. If you want a gun for home defense and shooting at the range, go with a short barrel. Pistols kill people, I am sure an 11.5″ barrel will kill people also.

  • Mike k July 21, 2017, 8:47 am

    Why the military picked 14.5″. I believe it is because at 14.5″ the length from the bayonet lug to the flash hider is the same as the 20″ model. This allows use of all the bayonets the military already had.

    • Jake July 21, 2017, 12:13 pm

      Are you being sarcastic?

  • Rick July 21, 2017, 5:12 am

    I have a few questions / comments. What is the best weapon for home self defense? Pistol, rifle, SBR? And, what caliber?

    You have talked a lot about size and speed of bullets. Doesn’t the bullet weight and construction have a lot to do w/ performance? Frangible, hollow point, ballistic tip, soft point, etc? In 5.56X45weights of – ~30gr up to ~80gr.

    I shot a chipmunk last week w/ my cheap pellet gun. I was using a ballistic tip pellet of standard weight. It blew the little critters insides out. Very small and slow but…. devastating.

    • Jay July 21, 2017, 9:31 am

      Rick the only real answer to that question is this, the best weapon to use for home defense is the one you have in your hand when the moment comes that you need it! End of story, anything else is BS. Research and use what you shoot the best at the distance your concerned with. Remember this, all calibers tested, look it up and watch real videos of this, on Sheetrock walls will go through several walls if you miss! Also, any firearm shot in the confines of a inside room will have your ears ringing!

    • Jerry Thomas July 21, 2017, 4:07 pm

      The good old boring 12 gauge. I believe more capacity is better, 8 shot +1. 00 buck pellets have 60 grains per pellet (more weight than a 22 caliber), 9 pellets per 2 3/4 inch shell, 9 shells x 9 pellets = 81 pellets bigger than a 22. That is a lot of fire power. Or you can use slugs or alternate slugs and 00 buck.

  • Gerry July 21, 2017, 4:48 am

    You are way too funny to with your quips. Were you a Marine as I was?

  • David Wosicki July 21, 2017, 4:46 am

    In your article you mention that AR-15 barrels run from 7″ all the way out to 36.” I have been looking for a 36″ barrel to build a custom AR-15 rifle around. (Also looking to do the same for an AR-10. Can you point me in the right direction as to where I can find a barrel maker who could make these for me?

    Thanks, and great article!

    David Wosicki

    • Altoids July 21, 2017, 6:21 am

      Not much point in a 36″ barrel. I have a 24″ version and muzzle velocities aren’t appreciably higher than what is claimed for a 20 inch barrel. I clock 55 grainers at just a tad over 3320. That little 5.56 x 45 mm case just doesn’t have the powder capacity to benefit from a barrel much longer than 20″.

    • Mark N. July 23, 2017, 3:17 am

      The original round was designed to achieve maximum velocity from a 20″ barrel. Since the round is already close to max fill and pressure capacity, you can gain little if any appreciable increase hand loading rounds for a three foot barrel.

  • Gerry July 21, 2017, 4:42 am

    Clay, with the shorter barrels, you’re forgetting the builders that are assembling an AR pistol. You should be a little more specific to cover them too.

  • Mark N. July 20, 2017, 8:01 pm

    Why do we need 2 (or more) ARs? They are all pretty much the same, except for the uppers. Having various calibers in different uppers is one thing, but complete rifles seems a bit much. The only difference between one lower or another, aside from style, is the trigger group, and as it is, you should have the best you can afford any way. If you are a competitor, well then OK, but for the rest of us, not so much.

    • KCshooter July 21, 2017, 6:22 am

      I have 5. Your opinion sucks.

      • Cary Kieffer July 21, 2017, 7:34 am

        +1 on what KC says…I have 11 and plans for 4 or 5 more…they are not all the same. I build my own and you have literally millions of combos to choose from. I’ve built 2 that I spent a lot of money on with no plans to shoot them, with Jack Skull receivers and flag cerakote jobs… When we were kids we didn’t want 1 matchbox car or 1 stormtrooper…..couldn’t have enough of either. Same with AR’s.

        • kb31416 July 21, 2017, 9:35 am

          Agreed with KC & Cary. I enjoy building them, including making with 80% lowers. I generally do a new AR project every month or so, and there is always something new and fun to do. In particular, I like the wildcat cartridges based on the 5.56 case that can be used in an AR with nothing but a barrel change. I have built several 300 AAC uppers, some rifle, and a pistol. The latest is a 277 Wolverine, which should be an even better deer killer than the 300 AAC. On the to-do list is also 7.62×40 WT, which is similar to the 300 AAC, but will do better with supersonic bullets than the AAC that was designed for subsonic rounds.
          Other AR projects include 7.62×39 and 5.45×39 rifles that I built to test the AK accuracy issue: is it the rifle or the ammo that makes AKs suck. I shot both in matches at 200 yards, and validated that it is not the cartridges, but the rifles.
          My new years resolution was “no more rifle projects!”, but I just got new AR barrels for 6.5 Grendel, 22 Nosler, a 24″ 5.56 Wylde barrel to make a match rifle (‘space gun’), and one that I can’t think of right now.
          Last point: why not have a built up lower for the upper to sit on? A bunch of loose uppers is borderline useless, and the lower is the less expensive part of the build anyway.
          As my wife has learned, an idle engineer is the devil’s workshop.

    • GRA July 21, 2017, 10:10 am

      Why more than one? I’ll give you my philosophy. I have at least one carbine for each caliber used most extensively by most militaries worldwide. I have an AR15 in 5.56, 7.62×39, and an ArmaLite DEF-10 carbine in .308 caliber. Regardless of how “paranoid” this may sound, I have at least one weapon that can fire each of those calibers thus allowing me to use a wider range of ammo (including enemy/invader ammo) if and when the need arises and allows me to be better prepared (even though I’m not a “prepper”) in the event of an invasion by the Useless Nations, China, or Mexico, etc,. This also serves a dual purpose as it allows me at least one caliber to hunt legally anywhere in the USA which is something I thoroughly enjoy. Keep in mind that the actual number of firearms you own is not the point but your ability to know very well each weapon you do have and you’re as accurate and competent as possible when firing each one is what’s most important. And when it comes to a long gun for home defense against the common criminal it is hard to beat a smooth operating 12 gauge with the minimum 18″ slug barrel.

    • singleshotcajun July 21, 2017, 3:04 pm

      need………………………………………………………………………………NEED? Somebody show this liberal out.

      • Mark N. July 23, 2017, 2:27 am

        Try again. It was the article that said we NEED more than 2 ARs. I questioned that. One AR 15 lower and as many different uppers as you want is one thing, but 5 or ten complete rifles? Where any upper will fit on any other lower, why? I didn’t say or even suggest that people should not HAVE more than one, whatever floats your boat, but I just don’t see the NEED for more than one, as if I am somehow obligated to go out an buy or build another rifle “just because I NEED one.” Sorry, not buying it. One suits me just fine. I mean, you can only shoot one at a time, and a caliber (upper) change takes seconds.

    • Russ H. July 21, 2017, 5:13 pm

      I have eight plus an AR10. Why? I enjoy building them in my retirement and no, they are NOT the same. Of the eight, two are similar but the rest are very different. I just don\’t what I\’ll do with 30-40! A friend suggested giving them away as gifts. Maybe…

  • Greg July 20, 2017, 1:28 pm

    Does a .223 wylde chambering add value or will 5.56 suffice?

    • Mark N. July 20, 2017, 7:57 pm

      Aside from allowing you to shoot either 5.56 or .223, the Wylde chamber is purported to allow for greater accuracy.

    • Old Sailor July 21, 2017, 12:12 pm

      Concur with Mark N. The 5.56 barrel will shoot either round. However, the .223 Wylde provides more accuracy. The 5.56 is a little less accurate when firing .223.

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