Weekly DTIC: The Fleet Yaw Problem, and Improving Rifle Effectiveness

5.56_M855A1_Enhanced_Performance_Round

Stepping out of the chronology that the past few Weekly DTIC entries have taken, today we’ll be examining two much more modern pieces of research, which help explain some of the phenomena observed by end-users when firing their weapons in anger. The first document is Small Caliber Lethality: 5.56mm Performance in Close Quarters Battle, by Majors Glenn Dean and David LaFontaine. This magazine article, originally published in September 2006 in Infantry Magazine, covers the results of Army Research Laboratory studies carried out to help determine the underlying cause of erratic terminal performance from 5.56mm weapons in the field. The second, Small-Caliber Projectile Target Impact Angle Determined from Close Proximity Radiographs, is a technical mate to the first, describing the process eventually used to generate the scientific data necessary for the fleet yaw theory.

The background of why these studies occurred should at this point be familiar to readers of TFB, but bears repeating. Essentially, recent infantry deployments resulted in reports of inadequate effectiveness from 5.56mm weapons – but, strangely, the reports were not uniform. Some units described their weapons as being highly effective, but others report having to make multiple hits on targets to have the desired effect. This was largely unexpected – the M855 5.56mm round produces very high muzzle energy for its caliber, and the projectile is designed to yaw violently – if not fragment – depositing its energy rapidly and effecting a stop. At short distances, it should have been very effective.

The first article explores this background, and the challenges the investigators had to face in very satisfying detail. What resulted from their investigation was a landmark discovery in terminal effectiveness science: Bullets – all bullets, not just .22 caliber ones – experience a period of very violent yaw and turbulence when they exit the muzzle, causing their angle of attack relative to their flight path – that is how “straight” the bullet is in flight – to vary wildly. Within 50m, they found, two bullets fired from the same gun, at essentially the same time, might impact a target at two completely different angles. A bullet impacting head on into gelatin would stay stable for much longer than one impacting at a high angle, and would deposit its energy much later. This explained the problems some users – but not others – were having with their weapons. In some instances, the FMJ projectiles would hit the target at a desirable high angle of attack, tumble and fragment within a short distance, and reliably stop the target, while in others, the same type of projectile would hit at a flat angle, and might not yaw for many inches.

Perhaps even more important than this discovery – in terms of the solutions it informed – was the fact that all projectiles tested, including 5.56mm, 5.45mm, 6.8mm, and 7.62mm projectiles of a wide variety of weights and types of construction, exhibited this flaw. While changing calibers to, for example, the 6.8mm Remington, might increase the energy per shot of service carbines, doing so would not solve the fleet yaw problem on a fundamental level. Further, it was determined that, while no such design currently existed on the commercial market, a projectile in the current 5.56mm chambering could be designed to overcome this effect, one which could yaw and fragment at all angles of attack, ensuring reliable terminal effects. These conclusions led directly to the four current in-service yaw-independent projectiles, M855A1, M80A1, Mk. 318, and Mk. 319.



Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • Esh325

    The British even complained about the .303 lacking lethality compared to old .577 round, so really I think bullet design is a much more important factor than caliber. If the M885A1 solves the problems the M885 had, it’s hard to say since there hasn’t really been any reports on its effectiveness. If militaries could use expanding projectiles, I think these concerns about the 5.56×45 would cease.

    • Initial field reports of M855A1 have been positive.

      • BillC

        Besides the rapid wear it creates on the barrels.

        • Joshua

          It’s not that bad. At 6,000 rounds our M4A1’s are shooting 5-6moa with M855A1. There is some extra wear but most is just regurgitated from 2 articles.

          6,000 rounds is acceptable for the button rifled non CHF M4A1 barrel.

          • iksnilol

            5-6 MOA out of an AR?!

            Thats shitty AK accuracy.

          • Joshua

            That’s after 6,000 rounds run hard through a M4A1 that has seen quite a bit of full auto.

            New we are pushing 1-1.5moa with M855A1

          • n0truscotsman

            That and barrels are cheap and easy to replace.

            It seems like an acceptable tradeoff to me.

          • Military ARs are rarely so well-tuned and sighted-in as civilian bench queens (even M4geries), not to mention that I’d feel pretty good about 5 MOA from a gun with almost ten grand of high pressure military ammo through it.

        • I’ve seen very little to corroborate that. One the one hand, I would expect M855A1’s projectile to exacerbate barrel wear somewhat, but on the other, the majority of wear comes from the flame-cutting effect of the propellant and M855A1 should be significantly easier on barrels in this respect due to its temperature stability.

          In short, so far as I know that was made up by rumormongering journalists of low integrity, and its connection to reality is further pretty tenuous.

          Even if M855A1 does increase barrel wear, it would have to do so by a lot to not be worth some of the advertised benefits.

          • valorius

            The dentist hates m855a1.

          • Dr. Roberts is very passionate about the subject, certainly.

    • J.T.

      The .303 rounds the Brits complained about were round nosed bullets. Once they switched to spitzer bullets, the effectiveness skyrocketed.

      • Esh325

        Yes, and back to my original point that it was bullet design and not caliber that is the problem.

        • buzzman1

          I don’t know. The .52 to .68 caliber bullets used in the civil war were devastatingly effective. The bullets were slow but created massive wounds.

    • BjornTheBrave

      Hey Esh, long time no speak bro. The A1 was designed as an improved penetration round but 5.56 sucks for that purpose anyway. I think we should standardize on the MK318 mod 0 as the general service round, use MK262 mod 1 for the distance/precision engangements, 70/75gr Nosler for the barrier blind applications (glass etc) and dump everything else. There’s no need for 5.56 FMJ’s, “enhanced penetrators” etc. Screw the Hague Convention, it was drafted 115 years ago. Who gives a hoot?? nothing lasts forever anyway.

      • M855A1 was designed as a general purpose round, with an emphasis on improved consistency of terminal effect, better barrier penetration, and better accuracy than M855, that these were the foci of the program is well documented. Further, if you look at the construction of modern purpose-designed dedicated armor penetrating projectiles, for example 5.8×42 DBP-10 or 5.45×39 7N22, they do not closely resemble M855A1 in construction.

        • BjornTheBrave

          I know it was envisioned with the GP role in mind. Getting better barrier penetration performance out of 5.56 is utterly useless though. This cartridge simply isn’t large enough for that purpose. Not powerful enough, not heavy enough. Not enough energy (as in transfer on target). 5.56 does fine in open terrain within the, say, 500m threshold depending on wheather conditions and barrel length. Since 5.56 was initially designed to rely on muzzle velocity and thorough powder burning the rule of thumb is: the longer the barrel the better. 14.7″ can be made a very capable platform, but I’d still rather want a 16″ setup to get the most out of it all. But like I said, ideal performance is when employed in open terrain. That’s what is was designed for. All else is to be chewed up by machineguns, grenade launchers, rocket launchers etc. You want good barrier penetration out of a GP rifle? Get an SGL21. When limited to riflemen only, an AK+HWS w/ FMJs for CQB/MOUT and an AR+ACOG 16″ w/ OTM/BTHP for longer range/open terrain engagements would be the ideal. Just my $0.02

          • 5.56mm seems just fine for going through most intermediate barriers, such as car windshields, doors, plywood, etc. It just doesn’t do that well when it’s trying to displace a lot of material, such as when trying to penetrate adobe or sandbags.

          • BjornTheBrave

            Yes, all true. I’m familiar with that presentation. I think I wasn’t specific enough in my explanation (mea culpa). When I mentioned barriers I had cinder blocks and other brickwork in mind. Glass and thin barriers of course aren’t any problem for 5.56 whatsoever. Nobody will deny that.

          • I don’t think 5.56mm has much problem with cinder blocks, judging by tests I’ve done, but it doesn’t fracture them like some larger rounds. Also, it works well on timber.

            Bricks, I’m not sure, and of course, it’s supposed to be not great vs. adobe.

          • BjornTheBrave

            The whole point of cutting through cinder blocks etc is to chew up the enemy’s cover and kill/wound him or either force him to manoeuvre (which might expose him). 5.56 will always be the inferior cartridge to 7.62 Soviet/NATO/Russian in that realm. Infantry deployment tactics is a team effort though. The right tool for the right job. A GP rifle has no business dealing with cover. We have rocket launchers, breach charges and machineguns to that end.

          • Bill

            This is actually a major point of people who disagree with some of the Big Army’s metrics. The M855 is an AP round. The M80 is ball. The M61 is the 7.62 NATO AP round. That presentation was comparing apples and oranges.

      • buzzman1

        The Marines loved the MK318 but are being force to use the A1 My personal feeling on this is a superior round is being pushed to the side by a radical environmentalist because it has lead in it.

        • A1 is cheaper and can be used on more ranges; I imagine that’s the reason.

      • How is everyone supposed to keep track of all those trajectories and zeroes.

      • valorius

        I seriously doubt m855a1 is going to suck at tactical barrier penetration.

    • Zachary marrs

      Also realize that when the .303 was created, the only way to make a better round was to make everything bigger as smokeless pwder and spitzer bullets did not yet exist

  • iksnilol

    Simple solution: explosives. Probably against the Hague convention though.

    • Steve Truffer

      Yes, you aren’t supposed to shoot explosive/incendiary rounds at people. Still think we just need to drop that whole FMJ affair.

      • Risky

        Yep… banning ‘dum dum’ bullets comes from a time when combatants had the good sense to sit out the war in a field hospital after getting shot in the arse. Now the field care of combatants we fight today involves rubbing some dirt on the wound, covering it with a piece of burlap and getting right back in the fight (or being handed a suicide vest). Time to adopt controlled expansion and put them down for good the first time. If it’s ‘humane’ enough for a deer its good enough for the Taliban.

        • Expanding ammunition has its own set of problems for military use, some related to the fleet yaw issue itself.

          • iksnilol

            What kind of issues?

            I honestly posted the first comment as some for of joke.

          • I haven’t seen some of the relevant tests, but secondary sources indicate that at least some JHPs don’t perform as designed when they hit at too high an angle of attack, exactly the opposite problem FMJs have, in other words. There’s enough variety of FMJs out there that I would expect some can remain consistent despite the fleet yaw effect, since both M855A1 and Mk. 318 are supposed to be yaw independent.

            If I were to guess, I’d say for maximum consistency, use a high velocity rifle shooting JHP/SP bullets with large openings and without bonded cores, if you’re worried about it. Even if they hit at too high an angle, they should fragment and deposit energy. However, you may be sacrificing penetration by doing this, which is arguably more important for taking game.

          • Cymond

            While a JHP that hits at too high of an angle may not expand or fragment as designed, would it be less effective than a FMJ at the same angle?
            Seriously, this fleet yaw concept is completely new to me.

          • It really depends on what JHPs you’re comparing to what FMJs. In some cases, yes, a JHP may be less effective than an FMJ at high angles of attack.

  • Steve Truffer

    I wonder if the standard jacket construction has anything to do with the issue. Inconsistency in base construction notably affects accuracy. This is alleviated by boat tails, and mostly solved by open tip designs. if there is a small gauge in the base, as it leaves the muzzle, that in effect causes a small “jet” that imbalances the bullet. This obviously leads to inaccuracy, and this yaw may be a component of the “Fleet yaw” issue. If ammo is assembled by machine, and a stray amount of lubricant falls into a press, it can dent the jacket (reloaders may experience this dent when over-lubing brass), and persist through a batch, or only affect a select few. The tools are cleaned or the lube is dislodged, and it disappears. The affected ammo may, in essence, be trading accuracy for yaw. As the ammo is likely assembled without individual supervision, this issue can present itself at random, with affected batches reaching some units and not others. Add in the random element of combat distribution, and one can easily see why reports vary.
    A multilateral and multifaceted conundrum.

    • Reverse-drawn OTM bullets were also tested, and found to exhibit the same yaw problem.

  • Nutat1on

    Always nice to see intelligent discussion driven by technical information as opposed to the flurry of marketing buzzwords and anecdotal accounts that normally surround anything to do with combat rifles and calibers. Kudos for taking the time to bring up DTIC studies and other proven technical material that many readers simply haven’t stumbled into yet. These kinds of articles make all of us a little more informed as a community.

  • Lance

    You cant beat yaw with a 62gr bullet generally 55gr 5.56mm rounds did far better in yaw and damage than over penetration 62gr ammo does.

    • Joshua

      Disagree, M855A1 is not yaw dependent thanks to its 3 part construction that pretty much guarantees the steel penetrator will break off and separate the jacket and slug.

      Also it was a requirement to fragment in soft tissue out to 600M from a M4, and it does.

    • Why would the net bullet weight have anything to do with yaw characteristics?

  • Zachary marrs

    If you want to see more “1 shot stops” with the 5.56, train the soilders better.
    Hell, there was an ollld fella who lived next to me, and every tear he’d go up north to hunt grizzly bears with an m1 carbine, and ever year, hed get a bear.
    Ballistics aren’t everything, accuracy is

    • Joshua

      One shot kills only exist if you get a brain shot, do not believe larger calibers compensate for poor shot placement. Seen plenty of guys take multiple shots COM from a Mk-17 and keep fighting.

      • Zachary marrs

        No, ive seen people drop like a rock from .22lr gut shots

        Lots of people who claim “dude, I shot him like , a gazillion times!” Most likely miss

        Instead of wasting millions of dollars to create the next wünder round, we should put that money into marksmanship. where did you get that I said larger calibers make up for poor shot placement?
        And look at my last sentence “ballistics aren’t everything, accuracy is”

        • Joshua

          Wasn’t referring specifically to you, just in general and your comment was already on the subject.

          Like I always say, sometimes guys just refuse to die. I fully agree about marksmanship, but M855A1 is a huge improvement over the SS109 bullet.

        • buzzman1

          Zach, When I went through IOBC eons ago they told use that WW2 had the highest rate of soldiers actually shooting at the enemy to kill them and that was 1 in 10. With the advent of automatic weapons the push was to teach soldiers to use suppressive fire and cover the maneuver element until they got close enough take a shot even a blind man could make. Wastes a lot of ammo. I believe they said we fired 1,000,000 rds of small arms ammo for every enemy dead in Vietnam.

      • dilby
        • Joshua

          The Mk-17 is also the SCAR-H in SOCOM.

          • buzzman1

            Josh, I have a SCAR-17L and its the most accurate rifle I’ve ever shot. Sub MOA with off the shelf ammo. Was hitting a head sized rock with no problem at 500m.

    • One of the recommendations of the last study was that soldiers be taught to use controlled pairs – basically double taps – to ensure both a hit and to greatly increase the probability of the bullet performing as designed.

      Worth noting is that accuracy means many different things, depending on the context. In the ’50s it was discovered that the vast majority of traditional marksmanship training wasn’t improving the combat effectiveness of the individual soldier. What worked on the range didn’t work in combat. Virtually all subsequent studies support this.

      • Zachary marrs

        Do you have a link to that?

        We wast A LOT of money on ammo
        250000 per kill in Afghanistan.
        Also cconsider wasteful programs like project salvo, aicw, oicw, etc

        The last thing the military wants to do is spend less money to improve marksmanship

        • Every time I hear shots fired per kill numbers, they are different. I don’t think anyone has a meaningful figure for the number of shots fired at a specific target versus the number of targets hit by aimed shots. How would one even start quantifying that?

          The key here is “traditional marksmanship training”, which is a specific kind of training that doesn’t account for stress. Several different techniques have since been developed to improve on this, one of which is just having a less intensive training regimen.

          Here’s a source to get you started.

          • Zachary marrs

            Traditional marksmanship is worthless for combat? You’ll get no argument from me.
            Nor did I say anything about “traditional marksmanship”, but even that would do a lot more good than the next 500 million dollar rifle that the military won’t adopt

            As for all the studies that say common engagements will not exceed 300 yards? Lol engagement distances depend on where you are fighting look at Afghanistan, they were digging out all the old m14’s due to the distances involved. Its a study, it won’t tell you the future, only the past.

          • Zachary marrs

            Ok so you got me on my m14 point, yet my other points still stand, if you want to spend a shit ton of money on the military, put it towards marksmanship training of all types, instead of the next wünder gun h&k shits out

          • I don’t think anyone was suggesting the Army adopt a weapon made by HK.

            The M855A1 seems like it fits very well with your goals here; it removes the lead content of the bullet, which has a number of advantages that get drowned out by chest-thumping anti-eco talk:

            1. Lead has historically been a strategic material during wartime, and nations with no eco-friendly movement at all have taken steps to reduce the amount of lead used per bullet fired (e.g., 7.92mm S.m.E, 7.62x54R LPS, 7.62×39 M43, DBP-89, etc).

            2. Lead is brittle and soft, which is a hinderance to making bullets with precisely controlled terminal characteristics.

            3. While it may be silly to worry about lead in the environment when there’s a war on (which, by the way, is a consideration that was incorporated into M855A1 development early on, contrary to what some gunwriters would have you believe), consideration should be paid to what ranges soldiers can train on. If units are being turned away from ranges citing environmental concerns – especially when abroad, then it makes sense to accommodate those concerns.

            So in other words, M855A1 will (theoretically) allow more regular access to ranges, and thus more marksmanship training, which is a good thing.

          • Zachary marrs

            On the h&k comment; the g11 was the child of the project salvo and oicw programs, which traded in marksmanship training for lots of tiny bullets fired at once. The only criticism I have is that the 5.56 isn’t the best round for long range shooting. Yes, it will work, but it isnt the best option.

          • OICW post-dated the G11. The G11 is also only tangentially related to Project SALVO, though several descendants of that program competed in the same ACR program that the G11 did. Further, the AR-15 family is the product of Project SALVO, as well.

            The G11 was tested and rejected. Are you saying they shouldn’t have tested it? I’m a little confused.

          • Zachary marrs

            No, the military has a bad habit of throwing money away the military wont change the ar platform for anything short of a laser rifle, yet they spend buku bucks for something only .001% better, only to keep on with the ar 15

          • Huh? The US military didn’t spend any money developing the G11.

          • Zachary marrs

            The g11 is just an example, how much did we spend on project salvo, or the oicw program?

          • I don’t feel that SALVO was a waste at all; it led directly to the weapons we have now. Sure, SPIW didn’t see service, but even in trying, it produced results.

            OICW; time will tell. I certainly think they gave it a good effort, and the fruits of that labor have neither ripened nor rotted yet.

            I’m still unclear as to what you mean, though. It kind of sounds like you’re arguing that military research and development shouldn’t endeavor to improve individual infantry weapons. Is that accurate?

          • Zachary marrs

            Its not that, its the fact that we spend a lot of money to create a new weapon that will never see the light of day, instead of spending less to make actual improvements on current systems, and it would be better to have a single, large program that is constantly going on, instaed of one every once and awhile

          • I suppose so, but research programs often don’t bear flashy tangible fruit like that, but I still would consider them necessary.

          • seans

            It wasn’t engagements didn’t happen past 300 meters, it was the majority of kills, which makes plenty of sense when coupled with the marksmanship training and iron sights.

    • buzzman1

      Not doubting your word about the guy but he was really good at shot placement. The M-1 carbine performed so badly in WW2 that there were congressional investigations about it after the war.
      I have to first hand accounts of the M-1 carbine. The first one was a deer a saw at a game check in station. It had been shot 18 times with an M1 carbine (poor shot placement) and the kill shot was a lucky shot to the back of the head. The second was a deer I killed with an M1 carbine. The first shot was a heart shot at about 100 yds. The deer took off and I found no blood trail so I just waited for awhile and started looking for it. About an hour later I found it hiding under a downed tree. It got up and I shot it in the shoulder from 20 meters knocking it back down. It started to get back up again and I put one in the back of its skull. When I dressed out the Buck I found my initial shot had passed through its hear and out the other side with no expansion. The shoulder shot hit the deers scapula and splattered. The third shot did the same but killed the deer by internal decapitation. Not a round I would want to rely on.

      • Zachary marrs

        No. Shut the hell up w/ that gun shop bs

        1, the rumors that the m1 carbine was no good was korea, and the claims that it sucked were found to be bullshit
        2. I commonly use my m1 w/ ball loads on hogs, and ive never had to shoot twice
        3. The previous DTIC post has this exact debate; look it up
        4. The m1 carbine was a favorite of jim cirillo who was in the nypd sou, loved the m1 carbine, giving it a 95% 1 shot kill rate, it was also a favorite of audie Murphey

        As for your deer story, ive used mine for deer hunting, as long as you stay under 100 yards, you will have no problem

        • buzzman1

          Zach, Sorry but my examples were first hand and not something a heard. I’m glad you have had good experiences with it but I haven’t. I used it for a plinking gun for a long time then sold it.
          As far as the congressional even the stenographer blurted out he had shot a german soldier multiple times before dropping him.
          Audie was a small man and also became an officer. Officers in WW2 didn’t carry Garand’s, they carried Carbines.

          • Zachary marrs

            I imagine if audie Murphy wanted an m1 garand, he would’ve gotten one. Do you have a link to the Congressional hearing? Shit, I guess if the stenographer said that, it must be true
            Ill say it again, the only reports of the m1 carbines ineffectiveness came from korea, and when those claims were investigated, it was found that the problem was the fact the solders were missing.

            So you shot 1 deer and didn’t kill it? Ive seen deer take a .45-70 to the brain and run over 100 yards, does that mean the .45-70 is ineffective?

          • buzzman1

            Dude calm down. I just don’t share your enthusiasm for the round. I’m glad you have had good experiences but I haven’t.

          • Zachary marrs

            Its not enthusiasm, I just choose to brlive the facts. I once had a guy tell me that he shot at and hit a woodchuck over 15+ times with the m1 carbine, and didnt kill it

            I cant find ANYTHING on a congressional investigation on the m1 carbine, none, nothing about it in any edition of warbaby, no info online, nothing. All military studies on it attributed the mythical lack of stoping power to bad shooting.

            Do not trash the round with lies, its annoying, and I’m tired of it. Do you actually have any facts at all, other than “well, aw shawt dis hurr deer, but it wus tha guns fawt thawt he run awf!”

          • buzzman1

            Yeah I think someone was full of it (and a little stupid) if they tried to say the shot a woodchuck 15 times with a carbine and didn’t kill it would be hard to not to call them a liar.
            Lots of things aren’t on the internet yet but I’m sure there is something about the congressional investigation.

          • Zachary marrs

            I can find nothing, at all, ive talked to larry ruth, and he never said anything about a congressional hearing, there are no mentions of it anywhere, which begs the question, how do you know of it? Did you tell mr ruth so he can update his tomes?

            Wait, dont tell me, you heard it at the local gun store.

            By your logic, if someone brings up evidence that the sky is blue, they are wrong because you have information that only you have, that says that is wrong.

          • buzzman1

            Read about it in a book a long time ago. Try it sometime. I’m looking right now and if I find anything I’ll send you the link.

  • Xaun Loc

    Interesting…. If I read this blurb correctly, they are saying that the problem with 5.56mm close in erratic lethality is that sometimes the bullets DON’T keyhole. Apparently every 5.56 round that I have ever fired into paper at 25 meters would have been ineffective as none of them ever showed any signs of keyholing.

    • allannon

      Yea. The military doesn’t broadly use HP or similar ammo because of some accord or other (to which, I believe, the US abides but isn’t a signatory).

      So instead they design ammo to keyhole to impart kinetic energy, and sometimes fragment to increase wound channels.

      Being civvies, we have different options and needs. For paper you donn’t want keyholing (reduces precision), and for game or defense we can just use HP.

      • Xaun Loc

        I got that. I guess I should have been more clear that when I said “every 5.56 round that I have ever fired into paper at 25 meters” I was talking about hundreds of rounds of issue military ammo, fired into standard zeroing targets – and the same was true of thousands of rounds that were fired by the soldiers I was training. Bottom line, I have NEVER seen any sign of keyholing with Army issue 5.56 out of any flavor M16 or M4 at 25 meters. If these rounds need to keyhole in order to work then none of them will ever work at short range.

        • allannon

          I think it’s normally the opposite problem, in that they stabilize at longer ranges. The rounds should also should remain fairly stable in flight, but will keyhole significantly (“yaw”) when it encounters resistance. Kinda like a car hydroplaning a bit, but going butt-sideways when it hits a patch of drier pavement.

          My read of the article is that the bullets to an unexpected degree coming out of the muzzle, and may or have a “good” approach angle. Those that are a bit off-axis keyhole and fragment, resulting in swift kills; those that happen to strike nose-on (or maybe below a certain angle off-axis) are less likely to behave properly, and instead act like a regular FMJ and poke a much less damaging hole through the target.

          So you wouldn’t necessarily see keyholing on paper, because they’re not that far off true; you might see different behavior of you stacked some cardboard behind it, or similarly offered some significant resistance.

          Back regarding the study, they’re probably looking to ensure that even with the unexpected and unpredictable yaw, bullets still fragment and keyhole on impact correctly. (Since they’re ignoring the KISS solution of just using hollow- or soft-points.)

          • buzzman1

            Yaw is often induced with rounds heavier base halves than front haves. Causes the base to try to try to pass the tip when the tip impacts something solid. Screws up penetration. The MK318 retained the mushrooming effect with the lead in the front and solved the penetration problem with a brass plug penetrator. And its a very accurate round.

          • The front half of Mk. 318 fragments, it doesn’t usually mushroom. It’s sort of half M193 with the opening at the front end, half brass solid.

      • See my comment above.

    • Keyholing is tumbling end over end. Fleet yaw describes the precession that all bullets have when they leave the muzzle, before they settle into their rotational cycle. They are two different things.

      • buzzman1

        If a bullet is key holing paper at any distance you need to throw away your ammo and try another brand and if that doesn’t work have your rifle checked out by a good gunsmith because its not safe to shoot.
        BTW you aren’t going to be able to hit anything with a bullet flying that erratically.

        • Keyholing and fleet yaw are two different things. The behavior exhibited by the projectiles tested was not keyholing.

  • Tierlieb

    So what now?

    Back to the 55gr M193, which was reported as fragmenting reliably and removed allegedly because it was considered inhumane?

    Looking at the hollow-tip design of the 5.45×39 which does yaw very reliable because its instability is inherent in the design?

    Standardising on the copper-based “brown tip” ammo that SF are supposedly happy with?

    • M855A1 was a direct outgrowth of the research in this article. Initial field tests have been positive.

  • Paul O.

    “Within 50m, they found, two bullets fired from the same gun, at
    essentially the same time, might impact a target at two completely
    different angles.” I just find that hard to believe. This goes against all previous ballistic experience. In short, you couldn’t shoot decent groups if what they assert is true.

    • Cymond

      The article claims this happens within 50m, but apparently only within 50m. Don’t ask me how this makes sense, but apparently the projectiles stabilize at some point.

      • Capt. Obvious

        See my “pumpkin test” comment down below. Also check out this video. They do stabilize somewhere between 75-100 yards (depending on barrel length and twist). http://youtu.be/YqY1nWjrrD8?list=UUzNTMIaoIgiwX42vmqpR7Hg

      • Bullets “settle down” in flight after 50m because they are spin-stabilized, but the conditions when leaving the bore of the rifle are extremely turbulent.

    • Two bullets fired at the same time at a target at the exact same distance should impact in the same place, provided the rifle and shooter are doing their job. However, when talking about targets that are moving even slightly, this may not be the case.

      • buzzman1

        Nathaniel- Did they test the rounds from both cold and very hot barrels? The ballistics change a lot.

        • Not to my knowledge. They did, however, test rounds at different pressures, which probably amounts to the same thing.

          • buzzman1

            Thought of something else. Dredging stuff up from a long time ago. Did anyone examine the test weapons barrels for throat damage. Weapons that shoot high pressure loads suffer damage to the throat area of the barrel which greatly affects accuracy and reliable round placement. It could be that improvements to barrels and the proper fitting of the barrel to the receiver is the fix to the problem. But after saying that I have trained thousands of soldiers and only a handful were good shots. Most couldn’t hit the side of a barn with birdshot at 10 feet so the whole concept of this article is purely for intellectual conversation purposes.

          • Considering that most of the rounds tested were from new Mann barrels with no erosion, and didn’t possess unusual pressure characteristics, I don’t think that’s likely.

          • buzzman1

            I would say you are correct knowing that. You have a baseline to work from. However, as someone else stated Military ARs are not was well made/fitted together as the hanger queens people have.
            If they were the top shooters in the military would use them.
            However, unless a bullet design can be made in a cost effective way I don’t think your research will benefit many people. Most soldiers even aiming at the enemy shoot maybe not badly but definitely not well and even those who do shoot well suffer from no range time when at home. And better weapons is a must. The army has to embrace a modular design like the Beretta ARX design where longer or shorter barrels can be used per mission requirements. In the open areas of Iraq and Afghanistan the longer barrels should be used to attain the longer range lethality. The M855 round gave the army the ability to shorten the barrel without sacrificing range as compared to the M-16A1. That allowed soldiers to get in and out of vehicles easier and faster. We also have to change doctrine from suppressive fire to accurate fire. Lots to work on besides the bullet.

  • Rob

    What does the “Fleet” in Fleet Yaw refer to? I understand the concept of bullet yaw and nutation, but I haven’t seen this term before. Does it refer to the idea that the yaw variability dampens quickly and is “fleeting”?

    • I would love to be a know-it-all and come up with some smart-sounding explanation, but, plain and simple, I have no idea.

    • Zachary marrs

      Fleet yaw has to do with the inescapable differences in the rifle and bullet

      • Rob

        I understand what it is. But why is it called “Fleet”? It might as
        well be called “purple” yaw unless there is a reason and meaning for the
        term used.

        • Zachary marrs

          I honestly have no clue, sorry. Im a big bore guy, so lots of this is new to me, lol

  • Capt. Obvious

    Here’s a test for you: This fall go gather up some pumpkins and set them at 25, 50, 75 and 100 yards. Shoot 1 shot each from a 16″ AR with 5.56 ammo. You’ll be amazed at the size of the entry and exit holes at the closer ranges, but by 100 yards it’s a nice round.22 hole, in-and-out.

    • Zachary marrs

      You aren’t comparing a human to a pumpkin are you?

  • JN

    I’ve described the same phenomenon to customers for whom I build long-range rifles. Calibers like .338 Lapua that require a high-enough twist rate to continue to stabilize the bullet out past a mile must be over-stabilized during the beginning of their exterior ballistic trajectory. This comes into play when you build a rifle with a specific accuracy guarantee. If the rifle shoots a 1″ (1MOA) group at 100 yards, it still may shoot a 1″ (1/4 MOA) group at 400 yards. I believe the bullet is not only wobbling when it hits the 100 yard target, but it is traveling on a helical path.

    I think the 7-twist trend in the 5.56 world achieves the same result.

    • What’s interesting is that they determined that over-stabilization was not the problem. Even with bullets with much more relaxed stability than M855 from a 1-in-7 twist barrel experienced the same fleet yaw effect.

      • JN

        Certainly- I don’t know how many rifles that I have built have been used on non-inanimate targets (based of the profession of my customers) , but the primary issue I address is accuracy. Like most rifle builders, I leave the terminal ballistics to the customer by choice of caliber, bullet, and load.

        I believe the characteristic I see with regards to this article are related but addressed as different problems. Thank you for this article!

  • buzzman1

    So where is the follow up with showing the flight patterns and ballistics of the new rounds? As far as reports of inconsistent lethality of the M855 round I have to ask why you were surprised. This has been a problem with the 5.56 round from day one. Did anyone bother to test each round with different barrel lengths? Manufacturers? Ammo Manufacturers? Israeli Arms makes about 15% of our rifle ammo and Lake city makes the rest. Which makers ammo performs the best. Looks like too little testing was done to write a real article.
    BTW I have heard anecdotal reports of the M855A1 rounds falling apart.

    • Really? Initial reports of the .223 round used in Indochina showed it performing better than .30-06.

  • valorius

    Indirect fires do mot suffer these same problems….. >:}

    “Shot, over.”

    • It seems that for ROE reasons, they’re moving away from indirect fire explosive weapons to direct fire ones. Even so, I’m sure the troops will be happy to receive 84mms of Swedish comfort.

  • Pete

    I think the germans had a solution on Sturmgewehr 44 where they put an attachment on the barrel which made the bullet leave the barrel in an angle. This seems not to have been very common from what I have read.

    • Those were for shooting out of ports on AFVs and did not work very well at that. They had nothing to do with improving the terminal effectiveness of the projectiles.