TFBTV: Myth Busting: Are Longer AR15 Barrels More Accurate?

In this episode of TFBTV, James uses a Caldwell Lead Sled DFT with an FN M4 (14.5″ barrel) and FN M16 (20″ barrel) to informally test the myth that longer barrels are more accurate. In this test, James uses four different types of inexpensive 55gr range ammo (courtesy of Ventura Munitions) – CBC 55gr M193; Wolf Gold 55gr; Wolf Polycase 55gr, and; Georgia Arms reloaded 55gr. Which comes out on top? The longer or shorter barrel?

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Transcript ….
[coming soon]

 






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  • iksnilol

    Anything with James in it is more attractive to ladies, sooo that’s crappy science if they involved James in the testing. It’s gonna skew the results.

    • schizuki

      I had to test that, so I showed my wife the video. She said she dropped an egg.

      • Carl Mumpower

        That really is funny!

      • Tassiebush

        Yeah it’s a little known fact that James is a leading cause of early menopause

    • Dr. Longfellow Buchenrad

      Are you insinuating that the M16 is a he and the M4 is a she?

      • iksnilol

        No, not at all. I just criticize the scientific validity of any scientific study involving James R. studying whether something is attractive or not. Whatever it is, it will by virtue of including James, be attractive.

        • Mystick

          Are you trying to tell us something with regards to your position relative to a closet? 😉

          • iksnilol

            No, I am sadly straight as an arrow. Am so confident in my sexuality that I can say that another man is attractive without “risking” being gay.

            Confidence, oughta try it.

  • Green Hell

    Longer barrel – faster bullet velocity. Or higher damage at longer range if you ask videogame developers.

    • valorius

      Or ballisticians.

    • Higher velocity will keep the bullet within the designed velocity range for terminal ballistics longer. Depending on the ammo going from a M-4 to a M-16 you will get 50-100% more range before the round exits below the minimum fragmentation velocity.

      So even though video games are sometimes wrong, in this one case they are right.

      • Tassiebush

        The military loads have been significantly tailored towards shorter barrels to the extent that the different barrel lengths don’t cause a huge difference in performance in velocity with current service loads. Nathaniel has covered it before either in comments or articles.

        • Tom Currie

          A longer barrel USUALLY produces greater muzzle velocity UNLESS the load is specifically tailored for a shorter barrel. This is often found in “pistol caliber” carbines where the 16″ barrel needed to avoid SBR tax and rules will actually give a lower MV than a somewhat shorter barrel. For example the original Thompson barrel was the right length to maximize velocity with the standard .45ACP load, but today’s 16″ barrel Thompsons actually produce a lower MV (which can be increased by shortening the barrel if you don’t mind jumping through hoops to make it an SBR.)

          One factor completely omitted in the discussion of longer barrel accuracy is that in most instances a longer barrel also yields a longer sight radius which can be a bigger factor than the change in MV.

          And, of course, no comparison of the accuracy of shorter vs longer barrels is valid unless both barrels are of equal quality and properly tuned.

          • Tassiebush

            Agreed on all points. I think another factor to go with barrel length and velocity is rate of twist. If someone makes or modifies a barrel too short to produce enough velocity to stabilise the projectile then clearly the barrel length results in poor accuracy albeit a faster twist would fix that too.

          • Cymond

            I suspect that sight radius is the underlying reason for the “longer barrels are more accurate” myth.

            OTOH, from what I understand, blackpowder is far more dependent on barrel length for velocity, so that could be the basis, too.

      • iksnilol

        Worst case scenario is 100% more frag range (that’s with shot out barrel and sub zero temps), more realistically it’s like 25-50% extra frag range.

        Still, the frag range for both the M16 and M4 is like a third of the effective range for the rifle. If frag range was everything, then an M16 would be outranged by an AKM.

    • micmac80

      Faster Bullet Also equals less wind drift and drop in unknown range scenario both would make bigger difference in grouping at say past 300m

      Test is in any case only legit if you used exact same barrel and cut it shorter for second part of the test .Differences barrel to barrel and gun to gun are far to large to test like this.Also when shooting groups fine reticle posibly high mag scope would help.

  • Green Hell

    I heard Colt just released some new revolver, why is everyone quiet?

    • Big Daddy

      Because it’s a colt revolver. if I want a new revolver honestly Ruger seems the way to go, an older revolver than S&W can’t be beat. I’ve owned and shot Colt revolvers and was not impressed. Jerry Miculek does a Youtube video on them and he’s spot on.

      • Joel

        Miculek has been sponsored by Colt’s main rival for a very long time.

        • Big Daddy

          Really…..try watching the video. After owning all 3 I agree with him 100% and he know a hell of a lot more than I do. I respect that, do you?

    • Oldtrader3

      Colt has released a new Cobra steel framed revolver. I hope that they sell a million of them. More available quality products never hurt the marketplace and this Colt seems to hit the mark. I wish Colt well and hope that they do better once more in the future, as a commercial entity, not just a Gov’t Contractor?

      • Bill

        I’m in, probably, thought the Cobra wouldn’t have been my first choice.

  • AC97

    TL;DW: Both are sufficiently accurate, any actual differences in accuracy are so negligible as to be a meaningless comparison for most applications, and 20 inch barrels are cooler.

    Next question?

    • Big Daddy

      Not if you have to work in confined spaces.

      • CommonSense23

        Or just work with a gun to begin with.

      • valorius

        So when do you reckon all US sniper rifles will be reduced in barrel length to 10″? 😉

      • AC97

        Practicality ≠ coolness

      • Bill

        It can be done, MOUT is a relatively new concept. It’s ironic that carbines originally went to horse soldiers fighting in wide open spaces.

        • Anonymoose

          Yeah, the 29″ nuggets were originally “cavalry carbines” back in the day, and a lot of other “cavalry carbines” had 20-24″ barrels.

  • ExMachina1

    I would only expect a noticable accuracy difference if you had used the iron sights. Shorter sight radius of the M4 should be a handicap

    • AC97

      And if you’re using a red dot sight or a scope, like you should be, that doesn’t matter.

    • Kivaari

      I use the same make and model scope on my 11.5″ and 16″ and so far I can’t see a difference. I have to admit I haven’t fired a great deal of ammo through the 11.5″ gun, just using the same WalMart “Perfecta” .223 55FMJ ammo. I suspect Perfecta, which they no longer seem to stock, was made by Fiocchi. It is some of the best ball ammo I’ve used. I highly recommend the Fiocchi 50 gr JHP ammo, it performs like match grade ammo.

    • valorius

      I’m waiting for all US military sniper rifles to be reduced in barrel length to 14.5″.

      Heck, why not 10″?

      • Uniform223

        this has to sting you quite a bit…

        http://i.imgur.com/pfNko8O.jpg

        The US Army’s CSASS will have a 16inch barrel… shame they didn’t just pick up the M110K

        If I remember correctly the SR-25 and M110 has a 20inch barrel when compared to the M24 which has a 24inch barrel…

        • CommonSense23

          Funny how also NSW is currently issuing free floated M4A1s to its snipers.

          • valorius

            They’re intended for use as suppressed platforms at closer ranges. For long range work long barrels will be retained until such time as guided bullets are issued.

          • iksnilol

            Nah, close range suppressed only snipers use 12 inch barrels with integrated suppressors (like the AI rifles).

          • valorius

            That’d be incorrect.

          • iksnilol

            Just google the AWC (Arctic Warfare Covert).

            It has a 12 inch barrel, fires 308, integral suppressor and folding stock. It’s also used by USSOCOM 1st SFOD-D , the SAS and German KSK.

            Soooo… politely sod off with your short barrel phobia.

          • valorius

            It is a special purpose niche weapon. Just like the new 16″ Army ‘sniper’ rifle is a niche weapon.

          • iksnilol

            Why sniper in quotes? If it is made for sniping, it’s a sniper rifle. Heck, Russians made a .22 LR sniper rifle.

          • valorius

            Because it’s a SOCOM niche weapon, not a general issue sniper weapon. Hence the quotations.

          • iksnilol

            Just because it’s a niche sniper rifle doesn’t mean it isn’t a sniper rifle.

          • Gary Kirk

            M4/M16s have always been issued to “snipers”. As backup weapons, I believe that you’re referring to the current use of said weapons as a stop gap for urban conflict where close precise fire is required, but may need to go full suppressive if needed and join the general fight like everyone else.

          • CommonSense23

            Its as a replacement for the MK12. When the 12s well pulled out of the armories due to the 20s they was a gap in capabilities. Until they realiized a M4A1 with a DD rail could fill the same capabilities as a MK12 out to 800 yards.

          • Gary Kirk

            Wouldn’t want to be the one behind it engaging at 800… Unless I was stuck in a valley village, where I was engaging constant at less than 8 meters.. Then guess I could.. For that moment take a couple pot shots.

        • valorius

          M24 is 24″, M40 is also 24″. M110 is 20″. M21 and m25 are 22″. Mk12 is the shorty of the bunch, it has an 18″.

          CSASS is a 16″ for a specific reason- it’s intended to be used suppressed. For which it gives up quite a lot of range vs the 20″ M110.

          • Gary Kirk

            Yes, the long barrels were for peak velocity, then shortened for theatre of ops, then further shortened for suppressed use. The LFAR style rifles original barrel lengths were for post gas port pressure to cycle the action properly, now we have the information/testing and gas block innovation to make them however long we’d like.

          • valorius

            For ‘true’ sniper work the long barrels will be retained at least until guided projectiles are fielded. The shorter lengths are for specific applications.

            Also, most US sniper systems are not based on the AR-15 platform.

          • Gary Kirk

            Yes!

          • Gary Kirk

            Nope, most are based on the 700..
            Hopefully we’ll be moving away from that soon, much better actions available now.. Instead of just applying chassis systems and what not, BUILD A DAMNED RIFLE..
            Sorry, just tired of the lipstick on a pig fixes…

          • valorius

            Erm, nope what? All the “700” based actions, and the M-14 based actions, all have long barrels.

          • Uniform223

            The SR-25 and M110 SASS… BOTH are designed to be suppressed.

            From my understanding the 16inch barrel requirement was supposed to make for a lighter and more compact rifle for DMR and Sniper roles.

          • iksnilol

            Not really, it still works just fine out to 800 meters, which is the recommended max range (at least according to the US Army) for the cartridge (7.62×51).

          • valorius

            OK sport.

          • iksnilol

            I’m just going from military manuals from the US Army, they don’t recommend 7.62×51 past 800 meters.

            And they’re right, it’s a crappy cartridge for long range.

          • valorius

            Enemy personnel have been engaged on countless occasions beyond 800 meters with M24 and M40 rifles, to great effect.

          • iksnilol

            Didn’t dispute that. Just saying that US military manuals recommend 7.62×51 from 800 to 1000 yards (1000 yards = 900 meters last I checked).

            Just like you can use a 7.62×39 at 500-600 meters doesn’t mean you should or that it is easy. Same applies to 7.62×51 at 1000 meters.

          • valorius

            I fully understand, having engaged (paper) targets at close to 600 meters with an M16A1, a weapon with a stated max range of 460 meters. 😉

          • iksnilol

            Lemme guess, after getting a good position and leisurely zeroing your weapon for a known range?

            Yeah, that’s sorta easy.

          • valorius

            If you think shooting a target at 600 meters with an M16A1 is easy, i invite you to try.

          • iksnilol

            Tighten sling, flip the sight to 600 meters, aquire sight picture, breathe out, squeeze trigger.

            I would love to try, but as it is, I don’t have a 600 meter range (the 1.500 meter range wasn’t available due to the winter being too hot) nor do I have an M16.

            Would an iron sighted 5.56 bolt gun suffice? I think I can borrow that.

          • valorius

            Sounds like a nice day at the range. Post us pics of your groups.

          • iksnilol

            I’ll take some next time I shoot.

      • Grindstone50k

        You sure are ate up over a simple comparison shoot.

        • valorius

          You sure have a lousy sarcasm detector.

          • Grindstone50k

            You’re right. Well played.

  • Edeco

    This analysis is OK as far as it goes… Sure they’re not inherently more accurate, usually*. But if going for accuracy, damn all else, I think one is goign to want maximum hose, simply because a 24-incher can be made stiff enough to get half-moa, and to scavenge velocity. A comprehensive formula for barrel whippy-ness would be neat, relate that to length and girth, thus to weight…

    *unless it just happens that a particular load is most consistent out of that barrel length. I admit internal ballistics is partially witchcraft to me. But that’s unlikely, particularly since 5.56 doesn’t have much powder to burn and many loads are pretty well developed.

    • schizuki

      It’s easier to make a short barrel stiffer that a long one. Longer = whippier.

      • Don Ward

        *Iksnilol hastily dabs the beads of sweat from his forehead*

        • Sgt. Stedenko

          Her

          • iksnilol

            Nope, I’ve got an Y chromosome. I just don’t have neurotic insecurities like you do, comrade.

      • Edeco

        I must’ve been unclear. Say I want a 20″ as stiff as a 24″, 0.950″ diameter 1:8 twist*… numerically, how thick does the 20″ have to be? Less than 0.950 right, but I don’t know of an existing formula that will give me a numba.

        *I have a feeling twist has a slight effect as well.

  • JumpIf NotZero

    No. Next question…

  • Gidge

    Shouldn’t you be using premium grade match ammo for a test like this? quite possible you’re limiting factor is the ammo and the best accuracy it can achieve

    • schizuki

      It’s a comparison. As long as both guns use the same ammo, it’s legit.

      • valorius

        In reality you’d have to test every kind of ammo and average them, since some barrels absolutely hate some ammo.

        • Twilight sparkle

          And have at least three of the same gun so you can get a more average representation of those firearms

          • BillC

            Try 30. You need 30 to get to parametric stats where averages come into play. Averages are used for lower samples because that’s what we are used to, even though with sample sizes lower the median should be used. Problem for us, we (and they) can’t afford 30+ guns for each group being tested.

    • derpmaster

      From my experience the limiting factor for most ARs is ammo. I can make a beat up rack grade 16″ shrubmaster from 15 years ago shoot dime sized groups with handloads. The platform is a lot more capable than most people give it credit for, but mil spec and commercial ammo is designed to be cheap and reliable, not particularly accurate. Comparisons like this video are for entertainment at best, however his overall conclusions are perfectly valid.

    • Jack

      What is wrong with this video? With a scope, 20″barrel, bench rest and decent ammo, He should be getting 1/2″ groups or at least moa 1″. This is at 100 yards , he should try shooting 200 yards and compare the groups

    • Mystick

      Why not overpressure proofing cartridges then?

  • Wetcoaster

    Out of curiosity, why 55gr loads? Wouldn’t 62gr rounds be more appropriate for those guns?

    • Kyle

      Beat me by like 30 seconds lol.

    • valorius

      It depends on the twist. for 1:12 barrels 55 would be best. For 62 1:8 or 1:9 is better. For 70gr plus, 1:7 would probably give the best results.

      • Anonymoose

        You can’t even shoot 62gr boattails (such as XM855) out of a 1:12 afaik. You need at least a 1:9, but then your upper limit would 69gr in boattails or 75gr flat-based.

        • valorius

          I was just speaking in terms of accuracy potential.

      • CommonSense23

        Except a 1in 7 will shoot when 40gr extremely well.

        • valorius

          40gr is massively overstabilized in a 1:7 barrel.

          • CommonSense23

            And what exactly is that going to cause.

          • valorius

            Suboptimal accuracy. For instance, M855A1 is more accurate from 1:8 and 1:9 twist barrels. I’m not saying 40gr won’t work in a 1:7, mind you. I qualified expert twice firing M193 from a M16A2’s 1:7.

          • CommonSense23

            Except faster twist rates greatly improve a rounds performance when it goes transonic.

          • valorius

            There are subtleties to any general rule, of course.

      • Wetcoaster

        Right. Both of the FN guns used have a 1:7 twist, which is why I was surprised SS109 or M855-alike ammo wasn’t used instead.

        Wolf and Georgia arms both sell 62gr FMJ rounds, with Georgia Arms even advertising it as SS109.

        On the one hand, I understand that it’s the ammo their sponsor sent them, and that 1:7 barrels should still stabilize 55gr ammo, but it is a little disappointing.

  • Kyle

    Why such light grain weights? A longer bullet in the 70+ grain category would run better through both rifles. I think that would be a better overall test. I’d do it myself but I only have a 16″ Carbine. A 20″ upper is on my wish list. That fat bastard Santa left me hanging this year.

    • Gary Kirk

      Still want to build a M16A1 Maybe then I can do a good 55gr test..

      • Stan Darsh

        If you’re thinking Green Mountain for the barrel, will it be a 1×12 or 1×14?

    • Grindstone50k

      Comparison, not a full accuracy test.

  • DudeLooksLikeTomBradyyyyy

    Longer sight radius of iron sights allows for more precise sight-alignment. Since most frequently iron sight radius tends to go hand in hand with barrel length, I can sort of see how this myth got started.

    This test should be re-done with iron-sights only.

    I realize this video is about “barrel length,” and that’s right, this video/test isolates barrel length by removing the iron-sight radius variable.

    But it would illustrate at least how the myth got started.

    • valorius

      A shorter barrel can be more accurate MOA wise, because it’s stiffer, but the longer barrel gives you advantages that come with more velocity- such as flatter trajectory, which equates to a longer MPBR and reduced TOF, reduced recoil (due to having more mass) therefore, more practical accuracy.

      • Uniform223

        for a quick and non scientific “test” and probably just for fun video… is it hurting you?

        “but the longer barrel gives you advantages that come with more velocity- such as flatter trajectory, which equates to a longer MPBR and reduced TOF, reduced recoil (due to having more mass) therefore, more practical accuracy.”

        > as and end user are you ever really going to notice that “practical accuracy”? Unless you go down range and evaluate the target, are you going to notice any overarching dramatic or even noticeable difference effect on your target? If all conditions and variables were the same with the exception of barrel length… 5.5inches… are you really going to perceive or notice it?

        • valorius

          You will certainly notice an increased MPBR, yes.

          I suspect you’ll also notice the enhanced wounding potential of a higher velocity impact, since it causes more dramatic fragmentation at any range where fragmentation occurs, not to mention increased fragmentation range to begin with.

          • Uniform223

            The M855A1 EPR, Mk262, and Mk318 rounds makes that argument incredibly negligible. Sometimes it’s not the length of the pipe, it’s what is coming out of it.

          • jono102

            Exactly, And also the nut behind the butt pulling the trigger. Training and marksmanship would be more important than a couple extra inches of barrel.

    • Ark

      Iron sights are irrelevant nowadays. Anyone doing serious shooting or real-world combat shooting is using an optic. The only reason to use irons is if your optic is broken or you’re fighting for a broke-ass army that can’t afford proper equipment. All other things held equal, the side with high-quality combat optics will decimate the side shooting entirely with irons.

    • Trey

      Not a myth just a function of Euclid being right and most designs taking advantage of that.

      I have seen match Small bore with the front sight on a rail beyond the muzzle but for most firearms Barrel length is also max sight distance forward

      As an aside there are also some rear sights further back than the receiver as well extending sight radius. Tang Sights come to mind.

  • Darrell

    Look like he failed to sight in the scope first, not that it necessarily matters.
    My 20″ Armalite will outshoot either of my 16″ guns, I know that.

  • valorius

    Interestingly, when increased range is desired in naval guns, tank guns and artillery pieces the barrel length is increased. See 16″/50 vs 16″/42, 5″/38 vs 5″/54 vs 5″/62.

    • Kivaari

      The 5″-38 and 5″-54 shoot different ammunition. The 54 is about 150% larger in both projectile length and case length. In Vietnam the 5″-38 could fire about 9 miles whereas the 5″-54 did 12 miles. The 38 projectile weighed about 50 pounds while the 54 was 74 pounds.
      The 38s were manually loaded unlike the automatic 54s.
      We fired hundreds of rounds of 5″-54 daily. While in harbors, like Da Nang, the attacks using 122mm rockets would stop. When we traded places with a 38 ship the attacks would begin. The 122mm had a range of just over 9 miles IIRC. Just outside the 38 ships range.

  • Gary Kirk

    Longer = more accurate.. Not necessarily, give this experiment.. Take proof test rigid mounted single shot tubes.. Length will only play into velocity, which can itself in turn play into “user” accuracy.. Only if, and that’s a BIG if, the end user could make use of a negligible amount of velocity increase. I for one personally prefer a 20″ barrel, but that’s just me. Rifles balance, and handle better to me..

  • Edeco

    Urm, yeah, that looks legit, but where I plug length in at? Is the equation in metric?*

    *kidding. Seriousely thanks I’ll have to try and absorb that, make an Excel chart.

  • atmar

    the m193 out of a 1:12 barrel is more accurate vs out of a 1:7 barrel

    • Gary Kirk

      Good point, but when in direct comparison.. Twist rate won’t matter, they’re only testing barrel length. So as long as they’re using the same ammo in both, and there is no bias towards one (a lead sled is pretty effective, but not perfect) the test is effective..

  • Anonymoose

    Free-floating and barrel profiles are more important within normal ranges than barrel length. It took me a long time to come to terms with this (I still prefer a 20″). Of course you will get more drop at longer range as your barrel gets shorter, but SBRs aren’t really long-range rifles, and people who try to make them into long-range rifles are sorely misguided.

  • kyphe

    Point of order! You do not test a myth, you test a claim to see if is is a myth or a reality.

  • WELLS SHANE

    Try the test at 300 meters

  • Sid Collins

    Dude, do you not own a mower or weedtrimmer? How are you going to pick up your spent casings in that tall grass?
    On a serious note, I was in the light infantry when the US Army transitioned from M16A1 to M16A2. Probably, that is where the “myth” or reality started. Heavier bullet, longer sight radius of iron sights, faster twist rate, heavier barrel. It was a huge improvement for all shooters. Suddenly, the 300 meter targets needed to be changed as frequently as all others.
    I like what you did, but would like to see you commit to some further tests. Ammo variety and range of targets.
    But thanks for what you did and what you do. I enjoy it.

  • Bradley

    I’m pretty sure this debate was over in any serious way about a century ago.

  • tb556

    shooting 100-200 yards won’t matter but shooting 300+ it will. You’re going to have way more bullet drop and a longer flight time which gives the wind more chance to push your bullet off target.

  • Dr. Longfellow Buchenrad

    Im pretty sure there are a lot of dimensional variables that affect accuracy considerably more than barrel length. Terminal ballistics ignored, all a longer barrel does is decrease your bullet drop over range and keep you out of the transonic region longer.

  • Sam

    Wish I could watch the video at work. Ground truths, longer does not equal more accurate, longer equals faster in similar barrels, longer barrel may give longer site radius (how many rifles don’t have barrel mounted sights?). Accuracy is a function of firearm and ammunition quality combined with shooters ability. As a match shooter 16.5 inch barreled AR’s do give up points to 20 inch. Velocity and sight radius apply. With new Service Rifle rules we may see if the difference is velocity or sight radius.
    Of the four ammunitions listed the Wolf Gold gives near match ammunition results at 100 yards for me. 1.25 MOA groups slung in, iron sights. Rifle is .75 MOA with MK262 or hand loaded 77’s on a rest. Have not shot Wolf on a rest yet. It’s been years since I shot GA reloads, the other ammo I have not shot.

  • Mystick

    Didn’t you all do this one already?

  • rick0857

    It has been my experience that the 1:7 twist rate for the M-4/M-16 must have at least a 62gr. bullet for ANY kind of accuracy. Every 55gr bullet I have fired through my 1:7 barrel falls low left on the target, however, when I shoot 62gr or higher weights my rounds hit where I aim.
    I believe he used the wrong ammo for this test from the start in these barrels.