.223/5.56 Velocity vs Length

556

Rifleshooter.com repeated their previous .300 Winmag test with a rifle chambered in .223/556.

He borrows his friend’s Remington 700 chambered in .223 Remington. They start at 26″ and cut the barrel down 1″ at a time until they get to 16.5″. They used a chopbox and a generator at the range to cut the barrel down. They did not bother re-crowning each cut. They use four different factory loaded cartridges; Remington UMC 223 Remington 55-grain U223R3, Federal XM193 5.56 M193 55-grain ball (the box is labeled both XM193 and M193 and has an 02 head stamp), Winchester M855 (08 head stamp) and Black Hills 223 68-grain Heavy Match ammunition.

 

There are tons of data that they collected. Go check it out.

 

223-barrel-length-v-velocity-graph


Nicholas C

Co-Founder of KRISSTALK forums, an owner’s support group and all things KRISS Vector related. Nick has been only been shooting for the past 3 years but found his passion through competitive shooting. USPSA and 3Gun. He loves all things that shoots and flashlights. Really really bright flashlights.


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  • NotoriousAPP

    What the hell is going on between 18 and 16″?

    • GUNxSPECTRE

      What? You don’t know about barrel fairies?

    • JumpIf NotZero

      Not sure. But when I looked into 18″ vs 16″ I had found a consistent difference of 50-75fps and that’s all. It was definitely worth it to lop off those two inches.

      My SPR can now easy be run as a carbine by just dropping the bipod and switching the scope for an aimpoint. This is just another small factor of why I’d never choose an 18″ AR. That said, I am considering a 20″.

      • Steve Truffer

        AK fanboy here, but don’t 18″ barrels allow for a rifle length gas tube, softening the recoil? Thought that was the whole point of an 18 inch barrel.

        • JumpIf NotZero

          Yes and No.

          18″ is the minimum to run rifle length (well, really 17.5″ iirc) but that doesn’t mean it’s a good idea. Both Noveske and KAC stopped production of their 18″ rifle gas length guns/barrels in favor of “intermediate” systems. Split between mid and rifle. Talking with John Noveske once about this, I was told they had more issues with their 18″ rifle length than any other gun they made, depending on ammo they could never be assured it was going to cycle – AT THE CORRECT – gas port size. Most 18″ rifle length is opened up to be larger than needed, it’s basically identical to midlength at that point. Both of those companies 20″ lengths are still rifle.

          I had a 13.7″ midlength. A good friend has a 12.5″ midlength. Neither of those are supposed to work but they do. The 12.5″ is suppressed-only with a tuned gas port. I really don’t think that gun is any smoother than my 12.5″ carbine length suppressed. They feel identical except his gun is heavier than mine.

          There is far more to how “smooth”/”soft” a gun runs than just the port distance from the chamber. Port size, carrier type, buffer type and weight, rifle/carbine/custom spring, ammo, suppressor or not, brake/comp or not, and weight of the gun itself are all factors. To think that “rifle length will run softer” is beyond simplifying a solution.

          • Steve Truffer

            Welp, thats why I asked. I’ll stick with AK’s and VZ’s

          • JumpIf NotZero

            Same issue with AK and VZ. They just chose to overgass the guns all the time. That said, the VZ is a cool gun.

            There are intricacies with the AK platform as well. I wouldn’t let the technical explanations scare you from an AR. Living in the USA or Canada, the AR-15 is a MUST OWN. For the most part they are actually “better” guns for first world inhabitants that are likely to keep their things dry and clean. If you were a child solider, Somali pirate, middle eastern extremist however, I’d recommend AK in an instant…. also a different career path.

            People who own AK’s, clean them, oil them, and then struggle to do simple things like place optics/slings, refine action, triggers, etc, are a mystery to me.

          • Steve Truffer

            I know AK’s and learning Vz’s. I don’t like the ergonomics of an AR (absolutely uncomfortable to shoulder, borderline painful to shoot), but admire the modularity. If Sigs were AR/ AK priced, and chambered in 5.45, I’d be all over them.

    • Mack

      THIS! if this could be explained i would be much interested!

  • http://196800revolutionsperminute.blogspot.com/ Nathaniel F.

    I wish they had been able to go down to 10″ (obviously that would require an SBR stamp), but this is still a significant bit of research.

    • Ken
      • http://196800revolutionsperminute.blogspot.com/ Nathaniel F.

        Unfortunately for .223 only.

        BBTI is a great website, though.

        • Steve

          It’s still pretty accurate. I have seen a more controlled test performed using 5.56 and the most interesting portion was the 10.5″ to 10″ jump – it was the only data point that showed a significantly different velocity reduction when compared with other equal length reductions.

          The .223 test that was linked appears to confirm this, though the cut length was greater.

          • http://196800revolutionsperminute.blogspot.com/ Nathaniel F.

            It’s low for 5.56, unfortunately. The curve is probably very close, though.

  • 101nomad

    Ain’t nobody better cut my barrel off.

  • MAXIMUS

    Here are two good links to review

    http://www.dtic.mil/ndia/2010armament/WednesdayCumberlandPhilipDater.pdf

    http://www.tacticaloperations.com/SWATbarrel/

    Not to mention the work NSWC Crane did, determining optimal barrel length for the MK12 SPR project.

    • JumpIf NotZero

      Mk12… Was a compromise between marine and army that wanted 16″ and 20″. Crane decided to split the difference.

    • http://196800revolutionsperminute.blogspot.com/ Nathaniel F.

      I very much like the muzzle pressure experiment, but it’s unfortunate that it gets quoted a lot as an authority on typical 5.56mm muzzle velocities.

  • Ken

    These guys cut the barrel all the way down to 3″ from 18.” I believe they use a pistol like a Thompson Center Contender or something.

    http://www.ballisticsbytheinch.com/223rifle.html

  • Giolli Joker

    I particularly enjoy this detail:
    “He borrows his friend’s Remington 700…”
    :-D

    • dp

      Insert “rich” between his & friend.

    • gunslinger

      and then cuts the barrel…

    • Ken

      LOLOLOLOL

  • dp

    This has been done many times before, so hardly expected any big surprises. What may be a surprise is variation between ammo makes. I recall reading a text by foremost ballistician Bill Davis Jr. on the subject more than 20years ago. I believe it was called “Gas expansion ratio vs. barrel length”.

  • gunslinger

    ya know i could expect to see one “hump” in the graph. basically there should be a point where all powder burns and therefore provides no more acceleration in the barrel. so any additional barrel would offere friction to the bullet and thus reduce velocity. if the barrel is in that sweet spot, the moment accelertion is equal to 0, the bullet leaves the barrel and therefore didn’t “slow down” inside the barrel.

    however once you start reducing the barrel length again, you get less time for the powder to accelerate the bullet.

    what i don’t get is why you’d get a second “burst” of energy at smaller barrel lengths.

  • dp

    Here is another barrel length test: http://sadefensejournal.com/wp/?p=1093
    Quite recent actually.

  • Anonymous

    I added some lines to highlight the more common barrel lenghts, 17″ and 16″.
    http://puu.sh/8NT1I.jpg

  • michel Baikrich

    Sorry I speak only French and Spanish, but with Google translator is nor a problem in this Babel tower

    Interressante information

    Salut

    Michel

  • EstebanCafe

    He “borrowed” a friends R-700 and incrementally ‘cut the barrel down’ for this test ? Must be a VERY good friend. Well, maybe not anymore…

  • Nathan Redbeard

    Excellent information, but I must add one small recommendation: DO AWAY WITH THE STANDARD EXCEL 2007 CHART STYLE!!!!! Ever since I saw that in 2007, I have hated it with a passion. The colors of the lines, the sans-serif font, the way too light box…it is worthless.
    /Rant off
    As I said, great info, I love having it. Thanks again.

  • jamie

    “He borrows his friend’s Remington 700…”

    Sorry dude it shrunk.

  • dsafds

    Great. A chart on barrel lengths only prurie doge hunters can make use of. Thanks.