Testing AR Barrel Length Though Scientific Methods

barrel10

I have never been one to subscribe too much to the barrel length debate.  I do know that through my shooting I generally keep my .308 equipped with a 20in barrel and my .223/556 barrels vary from 14.5in to 20in, depending on the application.  While I understand that there is velocity loss though less gas expansion, I tend to look more at the repeatably of the shot. Is the barrel consistent enough to accurately put rounds down range as close together as possible?

The maximum velocity for the M855 projectile occurred in a 20-inch barrel. This is anticipated since the cartridge was designed specifically for this barrel length. Velocity drops rapidly as the barrel length decreases, especially below 10 inches where the velocity drops below 2,500 fps. M855 bullets traveling below 2,500 fps when impacting a target will not produce a lethal wound channel.

The maximum velocity for the M855 projectile occurred in a 20-inch barrel. This is anticipated since the cartridge was designed specifically for this barrel length. Velocity drops rapidly as the barrel length decreases, especially below 10 inches where the velocity drops below 2,500 fps. M855 bullets traveling below 2,500 fps when impacting a target will not produce a lethal wound channel.

You can change or even eliminate muzzle flash, muzzle blast and other things with cartridge building, muzzle devices and suppressors.  With accuracy you are limited to the barrel harmonics and loading rounds that will induce consistent harmonics and barrel whip.

This article takes a look at different 5.56 cartridges and how barrel length can change velocity, accuracy and lethality while also decreasing weapon function.

There has been a cultural shift from the 20-inch barrel length in the AR-15/M16 weapon systems chambered for the 5.56×45 NATO cartridge to progressively shorter barrels for the purpose of producing an increasingly more compact assault/entry weapon without resorting to a bull-pup design.  Simple usage of these short-barreled weapons has shown the necessity for both sound and flash suppression, the intensity of which (in exceptionally short barrel lengths) approached the intensity of a flash-bang diversion device.  This shift toward shorter barrels has resulted in the U.S. Army and Marine Corps adopting the 14.5-inch barreled M4 carbine with a re-design of the 5.56×45 from the 55 grain SS-109 to the 63 grain M855 ammunition to optimize this barrel length.  The differing bullet design also necessitated a change in the rifling twist rate from the original 1:12 inches to 1:7 inches.

For the entire article check out the link here: http://www.sadefensejournal.com/wp/?p=1093




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  • Andrew Hobby

    Everyone should read the linked article. it is very well written and very easy to understand for the less-scientific among us (i.e. me)

  • aweds1

    Seeing how 5.56mm SBRs in the 10-12.5in barrel length have grown in popularity, has anyone developed a round tailored for them?

    • echelon

      Not that I’m aware of commercially. I’ve made some of my own since I reload. I personally find the 11.5″ barrel to be the easiest to work with as far as reducing weight, OAL and still having decent velocities down range. 10″ would be the shortest I would consider I think. FWIW, YMMV, etc.

    • Zachary marrs

      While not exactly tailored for sbr’s, rounds like the mk 318 mod 0 and mk 262 mod 1 aren’t as dependent on velocity.

      If i am wrong, please correct me

      • Mk. 262 has a more fragile jacket than military FMJs, but it otherwise performs very similarly to them.

  • Pete Sheppard

    The above quote is the first time I’ve read that the M855 was optimized for 14.5″ barrels.

    • Arguably, FN’s SS109 was originally optimized for the Minimi and perhaps the FNC. The M16A2 didn’t exist when the SS109 was chosen by NATO. I cannot document what changes were made when the SS109 was adapted for US production as the XM855E1 and finally standardized as the M855. However, quality issues with early batches of the XM855E1 nearly killed the M16A1E1 program. The XM4 carbine came too late to have any influence on the original M855. Now, I can believe the claims that the new lead-free M855A1 has been optimized for the M4 carbine.

      • Kivaari

        The SS109 was initially promoted as being more humane than the M193. The Swedes were very anti-American during the Vietnam War era. They pushed for a load that would not make big wounds. What happened is the world jumped onboard with the SS109, only to see the wounds were greater, due to the increased RPM. The Swedes quietly bought new 5.56mm rifles and never mentioned how their idea of being more humane worked out. This is well documented in WBR and ACTA/Surga.(that’s from memory, I don’t want to crawl under the house to find the articles. Check out Fackler’s articles and it goes into great detail.

        • While that’s possible, if you look at the M855 specification, it uses the same jacket material, thickness, and cannelure as M193, with the center of gravity even further rearward. Given this, it’s difficult for me to imagine that it has wildly dissimilar terminal effect.

          • Kivaari

            Think about the increased RPM. Going from 1:12 twist to 1:7, the increase in RPM makes the bullet more likely to come apart. Look at the various “super varmint” bullets, when driven too fast the RPM will cause the bullet to vaporize in the air. Push the bullets too fast, and you will see a vapor trail and a puff, with none of the bullet getting to 100m. This has been written up in varmint magazines and in Wound Ballistics Review (International Wound Ballistic Association). I have witnesses it several times. It is easy to recreate the effect. Simply look in your reloading manual for the varmint bullets the lighter in weight the faster they can be driven. Then read the advisory regarding peak velocity. Then stuff them into a case that will drive the bullet too fast. It will literally turn into lead vapor.
            The government report out of Sweden ACTA Surgica (from memory) was created by Sweden to denounce the US using the M193 round. They were early investigators of the SS109 concept. Unfortunately the stills and high speed video was poorly done. The Swedes used soap blocks that did not account for temporary cavitation, not present in tissue. Shooting pigs of comparable size to a PAVN/VC fighters 100Kg. shows interesting results. But the Swedes put a few small pigs into the mix (under 50Kg) which showed dramatic expansion of the tissues. Giving the uninformed viewer how a M193 if shot into a 3 year old kid.
            They promoted the SS109 and decided to not report the increase in RPM that resulted in even more destructive wounds.
            As Fackler and his team found is the Swedes, Yugoslavians and Chinese using, pigs by Sweden and Yugoslavia and dogs in China, missed by using a repeatable substance. This was born the guidelines for Ordnance gelatin. With the now fully developed gelatin, the tests have consistency not available in other substances, especially live animals as used. The US Army used goats.
            The Swede study was actually interesting, as they “victim” was shot in a simulated combat setting, treated by field medics, loaded onto a medevac helo, flown to a more advanced field hospital, treated as a man would be treated. Valuable training for everyone. After the pig was stabilized and would most likely have lived with continued medical care given to men, the pig was euthanized.
            A soap block (or clay) which was used internationally for such studies leave a huge cavity, that shows maximum expansion, but not showing the permanent cavity (the cracks and channels left behind in tissue) but kept the shape where had it been tissue, would have reduced in size since the tissue was not ripped apart.
            Cleaning the wounds and making a good site that will heal was used, just like a human was treated.
            In the US Army tests, one interesting test was done to simulate what happened to Kennedy. How the muscles react when struck by a bullet in similar sites as JFK. All the silliness about Kennedy reacting to the “shot from the front” could be induced by a shot from the rear.
            I had the pleasure of being invited into the IWBA by Dr. Fackler himself. I have little tolerance for the fake studies done by the gun press, like the Marshall-Steele “study”. Fake ballistic journalism. Real studies exist. The 1970’s studies for the LEAA using a “computer man” gave results not expected by the .45 crowd. Simply because it was not based on just terminal ballistics, but factored in how well a shooter could handle different guns. A ,45 that can’t hit the target gets lower points. A 9mm (with old JHP ammo) and a .38 Special is more effectively, than any .45, simply because people can hit the target more times and better aimed.
            You can look at Ezell’s, “The AK47 Story”, and use the footnotes to access the original sources. I did and the University of Washington provided me with several pounds of research paper.

  • me ohmy

    army needs a more lethal bullet…55 grainers are just nasty to get bit by.

    • JumpIf NotZero

      Have you been hit with a 55gr bullet? Do you have any lethality studies that you can cite?

      • me ohmy

        yeah I *HAVE* been hit by a 55 grainer and look up the ballistics. the permanent cavity is WORSE with a 55 grain bullet for the first two hundred yards or primary engagement distances.
        the M855/SS-109 is too heavy and slows down the fps by about 500FPS out of an M-4, which is ALREADY been neutered by the loss of four inches of barrel length.
        I’ll tell ya what smartass.. how about I shoot you with BOTH rounds, you tell me which hurts more..

        • Calm down, buddy.

          SS109 produces between 2,900-2,950 ft/s from a new M4 barrel. M193 produces between 3,100-3,150 ft/s from the same; so hardly a 500 ft/s loss.

          M193 and SS109 perform very similarly in tissue, as well when impacting at the same velocity. Given that at 200m M193 is going about as fast (a little under 2,300 ft/s) as SS109/M855, there’s really very little difference, terminally speaking, between them.

          • me ohmy

            rifling twist is another thing the AIRFORCE still fields OLD.. and I do mean OLD M-16A1’s, with 1-12 barrels.. they never upgraded the uppers since they never even hit the MRBF area of stoppages. dropped by accident more often then fired in anger

          • To my knowledge, the Air Force never adopted the M16A1.

          • Kivaari

            Weren’t they all still AR15s, with some kind of GAU nomenclature?

          • The Air Force did actually use the term “M16”, just never the A1 variant.

            I am not qualified to describe the use of GAU nomenclature, sadly.

          • me ohmy

            subtle.. but yeah slab sides.. not the A1 config with forward assist
            The AR-15 was first adopted in 1962 by the United States Air Force, ultimately receiving the designation M16

        • JumpIf NotZero

          yeah I *HAVE* been hit by a 55 grainer
          lol

          I’ll tell ya what smartass.. how about I shoot you with BOTH rounds, you tell me which hurts more..
          Apparently people do still use this blatantly stupid argument, I had no idea.

          • Grindstone50k

            I’ll tell ya what smartass.. how about I shoot you with BOTH rounds, you tell me which hurts more..
            Apparently people do still use this blatantly stupid argument, I had no idea.

            To be fair, you did start off with that very same argument.

          • JumpIf NotZero

            Not even a little bit. I asked only his qualifications on the subject. Either first hand or if had some studies. He clearly has neither.

          • me ohmy

            and your quals are what.. mr space shuttle door gunner???

          • Holy crap that’s the coolest job description ever!

          • JumpIf NotZero

            🙂 Yea, we’ll disqus (get it? No, you probably don’t) my qualifications when I make bullshit claims like yours.

          • me ohmy

            BZzzzzz…zzzt I’m sorry your time to get my attention has unfortunately run out..
            what did he win Johnny??
            HE GETS A FREE LESSON IN REJECTION, BOB!!!
            From Speigle Chicago 60609…
            now sod off you nabob looking dirtshooter

          • me ohmy

            never claimed any quals there budrow.. just stating facts as I see em.

          • me ohmy

            again.. I answered him on BOTH counts….hardly F***ing “stupid”

        • Kivaari

          I knew a couple men shot with 5.56mm and 7.62×39. I followed them while healing. The M16 wound was insignificant and only hit tissue. He healed up fast. The other man, Was working in ‘Central America’ “, when his team inside “a country bordering El Salvador” took several hits to the torso. He lived and it took many months for him to heal. It ended his career. Only good hits count. And sometimes even good hits don’t kill.

          • me ohmy

            caliber doesnt define death..placement does.
            saw a fat chick killed with a 25ACP, which is less power then a 22LR, hit her just right in the upper chambers of her heart and she had tamponade from a minor bleeder and stopped her heart in the resulting pericardium clot.

    • n0truscotsman

      We already have 3 cartridges more lethal than M855 in service. Going back to 55 gr fmj would be a step backwards.

      • me ohmy

        under stabilised is nasty too , and yeah I know all about rhe MOD1’s and others….SIERRA builds a hall of a nice bullet and BLACK HILLS does a hell of a good round..but supply lines for that is a PITA.. ask ANYONE in the field.. getting specific ammo unless you are SPECFOR or other special operations, you rely on the supply line.. which SUCKS.

        • M855A1 is standardized. It should be widely available by now.

          • me ohmy

            is that the new green round or a better penetrator round?

          • It’s the yaw-independent round with a much larger penetrator than M855.

          • me ohmy

            interesting, so it upsets faster in a gelatin/flesh environment…
            I LIKE IT!!!!!!

  • There are a few issues with this article (which has been around for a while, and is usually cited whenever someone wants to “prove” that M855/the M4 is sublethal garbage).

    1. “This shift toward shorter barrels has resulted in the U.S. Army and Marine Corps adopting the 14.5-inch barreled M4 carbine with a re-design of the 5.56×45 from the 55 grain SS-109 to the 63 grain M855 ammunition to optimize this barrel length.” SS109 uses a 62 grain bullet, almost identical to (but distinct from) M855. Both were designed for the M16A2.

    2. M855 isn’t the reason the M4 has a 1/7 twist, the M856 tracer is.

    3. They are using completely unsupported velocity “thresholds” for lethality. At any velocity, 5.56mm bullets will tumble, and this will cause a large temporary cavity. At velocities above 2,100 ft/s, 55 and 62gr projectiles will fragment increasingly violently until at around 2,800 ft/s and above they begin to exhibit the familiar “confetti” pattern. With very short barrels and correspondingly low velocities, even though there is little fragmentation, there is still tumbling, large temporary cavity production, and tissue stretching happening at a rate that can cause remote wounding.

    4. The ammunition is chilled before firing. This has the effect of directly reducing the kinetic energy of the ammunition during firing. While this would not be an objectionable practice if the testers were simply comparing their own results, they make unsupported claims based on the results they get as to which barrels are “lethal”. This is supported by their 20″ barrel velocity being 2,979 ft/s. M855 spec from 20″ barrels is 3,113 ft/s.

    5. “M855 bullets traveling below 2,500 fps when impacting a target will not produce a lethal wound channel.” and “Equally illuminating in this study was the correlation between velocity and barrel length (see Graph 2). To generate a lethal wound channel, the M855 projectile must have a velocity of at least 2,500 ft/sec on impact with the target. Below that critical velocity, the M855 bullet simply drills a 1/4 inch hole in the target, which too frequently is not lethal unless it passes through a vital structure. “ These statements are ridiculous, and frankly irresponsible to put into print. At 2,500 ft/s, M855 is producing fully as much energy as an M1 Carbine, while having 500 ft/s more velocity. At this velocity, the projectile may break in half, causing great energy deposition. At this velocity, M855 is capable of penetrating all soft body armor and killing the target behind. At this velocity, the temporary stretch cavity is expanding fast enough to break bones and destroy organs.

    6. They say they are using Lake City ammunition. Given the low velocity, I have to wonder if they’re using an out-of-spec lot (often sold on the civilian market as surplus). It’s strange (though not indicting) that they put so much effort into obtaining even results, but did not bother to post the box the ammunition they used came in.

    7. There are a couple of “humps” where longer barrel lengths produce less velocity than shorter ones. This could be indicative of a procedural error.

    8. “The M855 ammunition is optimized for a 20-inch barrel with a 1:7 twist barrel. It was not surprising that the greatest velocity of 2,979 ft/sec was obtained in the 20-inch barrel, and the lower velocity on barrels greater than 20 inches is explained by decreased pressure driving the bullet no longer exceeding the slowing from friction. After all, Eugene Stoner designed the cartridge for the 20 inch barrel.” I frankly doubt this, but it’s possible, I guess. Why then does velocity begin to go up again at the 22″ mark? This seems most indicative of a procedural error to me.

    This criticism isn’t to suggest that the test had no merit. Their results for uncorking pressure and sound levels are very interesting. However, I suspect there were methodological problems and human error involved, and I am unhappy with how the results were used to come to completely spurious conclusions based on numbers pulled out of thin air.

    • me ohmy

      that’s a misquote.. the 55grain load WASNT the SS-109
      it was the M-193.. SS-109 was the same loading (almost) as the M855
      just saying to keep the numbers correct

      • It’s not a misquote. I copied and pasted it directly from the article.

        • me ohmy

          they mixed up the rounds then…sorry, thought somebody goofed

    • Russ

      Nate always argues on the margins then gets snarky when somebody disagrees. It’s unprofessional and unhealthy. The simple fact, simply stated is that shortening the barrel does absolutely nothing but degrade the performance of the 5.56 round. Plain and simple. Furthermore, the more that you shorten the barrel, the worse the performance gets. Now if Nate has some access to the new Army A1 round and reveals some new information, I’m willing to read it. Otherwise, let the dang horse die.

      • n0truscotsman

        Did you even read his last paragraph???

        Go back and re-read it.

      • I’m sorry you feel that I haven’t represented the site properly. If you’d like, I can send your complaint up the chain to Steve, and he’ll decide an appropriate course of action. Since you feel my criticism of the article was unfair, though, could you give me some more insight into what about it you felt was untoward?

        • Russ

          Sure send it on up and have him review your interaction with commenters. Many of us may be ignorant, ill informed or plain wrong but your tone and demeanor online makes us feel unwelcome and abused. I still visit the site but avoid your entries. I was unhappy with the way that you responded to a commenter and responded as I did. Your job is to encourage traffic to the TFB and not repel it. If I continue to find you interacting in other writer’s posts I’ll probably just scrape TFB off my favs.

          • As promised, I have sent these comments up the chain to Steve. I take my job here very seriously, and that includes my conduct in the comments section as well. Clearly, you feel very strongly about this; strongly enough to not want to read any posts with my name on it. I will not ignore or sweep under the rug those sorts of complaints when I receive them.

          • Mahhn

            outside person here, reading these comments for the first time, not knowing any of you. It sounded like yeah you have a lot of input, it did come across as politely calling the author and freaking idiot, while making good points. I just figured you were ripping them a new one and backing it up. With a human voice behind it, I have no doubt it would have sounded nicer. Text often gets taken more aggressive than it is meant. That said, everyone was right from their perspective, and everyone is different so our perspectives are rarely the same. Keep on commenting both of you, I’d rather see dialog than nothing. and at least it didn’t degrade to childish name calling.

          • Coming off as arrogant or insincere is a peril of the written format. It takes a lot of practice to avoid this, and I am yet young.

          • Kivaari

            Wrong, Shortening the barrel on a rifle, causes velocity to drop. It is why a M193 fired from a 20″ barrel will perform better than the same load fired from a 14.5″ barrel. In the 20″ rifle the bullet will tumble and break at the crimping grove The lower velocity provided by 14.5 or shorter barrels gives up that effect. The bullets remain intact, and the wounds are less ugly. It is strictly a matter of velocity and what tissue is impacted. Hit muscle can leave an insignificant wound. Hitting bone will be nasty.

          • Russ, maybe Nate said something snarky in the past (I don’t read every single comment on the site), but there was nothing snarky about his interaction in this instance. I encourage my writers to share their knowledge and interact with readers in the comments.

            We have many writers from many different backgrounds intentionally so there is a wide range of views and writing styles. I don’t want or encourage all our my team to each have universal appear … that would make for very bland bottom-of-the-barrel writing. If one writer does not appeal to you, hopefully others will.

          • Leonard

            Actually, not having to read your constant whining would be a huge relief for the vast majority of us. Don’t let the door hit you on the way out….

    • Kivaari

      Very good remarks about this paper.

    • AlDeLarge

      Didn’t you say energy and momentum were irrelevant?
      BTW: 62 gr @ 2500 fps is 88% as much energy and 70% as much momentum as 110 gr @ 2000 fps. Also, they said the round is effective at 2500 fps. Why are you saying they’re wrong, while saying the same thing?

      • Momentum is irrelevant. Energy is highly relevant, but it’s far from the whole story of terminal effectiveness.

        M1 Carbines may produce different velocities with different loads. The velocity I used was 1,900 ft/s, which produces very similar energy to a 62 gr bullet at 2,500 ft/s. 2,000 ft/s is also a reasonable velocity for this caliber.

        The idea that below 2,500 ft/s, 5.56 magically stops being lethal is what I am contesting. Or are you suggesting anything less powerful than an M1 Carbine is ineffective?

    • brainy37

      1. SS109 is a NATO spec, not an actual round. We base our M855 off of this spec as do other countries for uniformity reason. It’s also far from optimum as it was created with the purpose of penetration older Russian titanium and kelvar body armor which is no longer in use.
      2. Correct
      3. The M855 will cease to fragment at around 2500fps completely and stay fully intact. Only the heavier 77gr bullets will fragment at that low of a speed. Again the M855 is less than optimal.
      4. Odd that it was chilled but ok.
      5. The sentence should be redone to say it produces a less efficient
      wound channel. Energy deposition is a worthless stat since, with the
      exception of
      kidneys and liver, all other organs are elastic enough that it doesn’t
      do much.
      6. Agreed
      7. Stoner didn’t create the bullet but it was optimized for a 20in barrel. Except that it was optimized for the M197 55gr bullet, not the 62gr M855.

      The test is just another thing we can add to a large body of work on the AR15. While I wouldn’t call it conclusive due to some of the issues with methodology, it does add to the theories that we already knew.

      • 1. SS109 is the Fabrique Nationale factory designation for the round that became 5.56x45mm NATO. The NATO specification is 5.56x45mm NATO, not SS109. These names are often interchanged, as the rounds themselves are interchangeable and nearly identical.

        3. It must be understood that fragmentation is not something that either happens or it doesn’t. One of the issues I have with the idea of a “fragmentation threshold” is that projectiles fragment in several different ways depending on the characteristics of the shot and the velocity at which they are traveling. When most people think of “fragmentation” they imagine big confetti-esque shot wounds, with a virtually disintegrated bullet. In reality, M855 and SS109 will fragment down to somewhere above 2,100 ft/s – keep in mind this depends on the exact construction of the bullet, something as innocuous as a slightly deeper cannelure can greatly improve this factor, 2,100 ft/s essentially represents the basement for fragmentation – but shots above and below that velocity may well look very similar. So it must first be understood that fragmentation can mean dramatic, confetti-esque terminal effect, or something as simple as shards of lead separating from the core during travel and having little effect on the target.

        More importantly, M855 has very similar yaw characteristics to other rounds (M193, M67, M80, etc). This subject is plumbed in more detail in my post on the fleet yaw problem.

        5. While the effects of energy deposition are not as well understood as I should like them to be, energy deposition with regards to rifle projectiles is very important with regards to terminal effect. Here are some sources to get you started:

        http://www.dtic.mil/dtic/tr/fulltext/u2/a526059.pdf

        http://www.mediafire.com/view/q7a0600i0wgvz8h/The_Modelling_and_Application_of_Small_Arms_Wound_Ballistics.pdf

        7. Stoner did design the cartridge. From The Black Rifle, page 60:

        “In Gene Stoner’s personal, handwritten historical summary of these early events, he described this process as follows:

        ‘The cartridge development for the .223 was started by myself in 1957 after a trip to Fort Benning to get the desired military characteristics. I calculated the needed bullet weight and muzzle velocity. I then designed the bullet and had it manufactured by the Sierra Bullet Co. in Whittier, California. This bullet was a 55-grain boattail design with a jacket thickness of .018 inches. The powder finally selected was a standard commercial type. The chamber pressures for this round in the standard .222 case were a little excessive. The obvious conclusion was to increase the case capacity and to use a different powder. I contacted Winchester and Remington about loading the necessary rounds for the test progra… The ArmaLite rounds were loaded by Remington with the bullets furnished and were designated “.222 Special”.'”

        Note that Stoner’s 55 grain bullet design was not the same as that used in M193. His was a finer shape, with a much higher ballistic coefficient (about .149 vs. .120). I am actually fortunate enough to have one of these early rounds headstamped “.222 SPL” in my collection. There is circumstantial evidence, however, that some foreign ammunition (PMC XP193 in particular) still uses Stoner’s Sierra 55gr bullet design, instead of the Remington design that became M193.

    • Mazryonh

      Did you contact the journal and get a response about your criticisms of this study?

      • If you don’t mind me asking, what do you think that would accomplish?

      • Hyok Kim

        These people have a professional reputation to uphold. Once they say it in a journal, they’re bound to defend it tooth and nail.

        It will take a giant of a man to admit he errored in public.

  • Nicks87

    It’s funny how nobody ever argues about the lethality of the .308 cartridge…

    • Blake

      true dat

      the full-auto controlability & the weight of the ammo however…

      But then the US Govt was never known to be good at finding happy mediums, compromises, or optimization…

      • Kivaari

        Actually “NEEDING” full auto in a rifle is questionable. A warrior with a semi-auto AR15-type rifle would be very well armed. If I were young again, and still in the military or police, I would not be bothered by not having a select-fire rifle or SMG. I advocated issuing semi-auto versions of the Uzi and MP5 over 30 years ago. Having the FA setting was a waste of time. Fun, but no real need.

        • T Sheehan

          Most joes would disagree, especially when conducting battle drill 6 (room entry and clearance), which typically goes first to my automatic rifleman who doesn’t always have a SAW. He’s the first in (and usually the shortest guy on that fire team, for stacking reasons), and definitely doesn’t need semi or 3 round burst limitations if he stomps into a packed room from the fatal funnel. Spray and short barrels may be offensive to some purists, and certainly to bean counters, but they count when max lethality in cqb are the situation.

          • Kivaari

            I packed an MP5 for a decade. I have nothing against FA and short firearms. There are few cases where full-auto is useful. In a military setting there are a few places where suppressive fire is helpful. That is why soldiers pack an M249. It is why the Marines want a rifle like the Mk18, with big box magazines. The soldier or civilian police officer have very few places where FA gives them the edge they need. I’ve demonstrated this for government officials. Put up 5 steel humanoid targets at 15 feet (living room distance), hose the targets down with 30 rounds. Wow, often 5 targets are still standing.
            Then fire using 3 round bursts and they go down, but it took time. Then shoot fast in semi-auto and each target goes down and can be revisited.

          • T Sheehan

            We’ve done the shoot house ourselves doing the crawl-walk-run thing with both controlled pairs in choreography to teach fundamentals, and we’ve done lipstick and frangibles at messy combat speed. The 1-2 method is very pretty, and impressed the brass with its appearance of professionalism, but when the full auto let loose on groups, there was never a standing target. I’m not dismissing your entry practices, but I am saying both in training and in frantic, rapid combat CQB, the full auto SAW shorty was king and got the final word. We adjusted our SOP accordingly, but something a little more nimble is on the want list our entry guys, without sacrificing output and capacity. One even asked of we could get P-90’s on the MTOE, which caused much laughter.

          • Kivaari

            Very well stated. I have to relate more to LE than military use. I was a REMF in both the Army and Navy. Most of my training was civilian LE, where we did not have a belt fed machinegun for a base of fire. We never trained for warfare like out fighters in Iraq and Afghanistan do daily. With that in mind, I don’t think FA had a significant roll. We were drilled so well that we could run the course with the MP5 set on FA, and never leaving the finger on the trigger long enough to let two shots loose. Police have a much tighter frame work to stay inside, than warriors, where collateral damage was not a big deal. Having a limited amount of ammunition, initially we had 60 rounds with the MP5. Instead of extra ammo on my person I carried an extra radio and extra radio batteries. My G17 had 45 rounds (I always loaded down to 15 rounds per mag) and had 5 more .38 Spl. in my M642. In that setting FA just was not needed.
            It sure is fun. We trained hard, much more than many metropolitan police agencies. With the added training we knew our weapons well.
            I look back to my parents generation where the M1 rifles and carbines provided good outcomes. When I was in the Navy our armory aboard ship were all WW2 era designs. M1 rifles, BARs, M1911A1s and M1A1 SMGs. We only carried one M1919 and one M1 carbine. We picked up M2HBs for use while in the combat zone. Stateside we had an armed robbery from a ships crew that was getting the cash for paying a ships crew. No shots fired fortunately. Two officers with only 7 rounds each did not resist. The enlisted driver was unarmed.
            In the Army pistol skills were pretty much ignored. It was the early 80s when .45 ammo was in very short supply, and the M9 (and others) were being investigated as the replacement. It became hard to get .45 ammo even for armed details. I fired more ammo during PD training in one evolution, than I fired each year in the military.

          • Mazryonh

            What caused the laughter about the suggestion of adding P90s to the arsenal? Was it not proven back then?

    • Actually when .30 caliber rounds were new that was a very contentious topic indeed:

      http://looserounds.com/2014/10/17/what-are-they-good-for/

      • Kivaari

        Very true. The .30 US and .30-03, FMJ round nose loads just poked holes.

        • More to the point, I think any time something new comes along, people will doubt it.

          In the case of SCHV and the 5.56mm, the concept is well proven. That’s not to say there’s no room for argument, but I do think most of the objections come from people who either have something to sell or are influenced by those who do.

          I would urge readers of this comment not to take that as a dismissal of everyone with an opinion different than mine (there are some interesting and sound arguments to be made against what I am saying, though precious little supporting evidence that I’ve found so far to support them); it’s just an observation. Those who read enough gun magazines which have rifles and dead trees to sell (that everyone’s already bought – but for the chambering) risk their opinions being colored by that.

          • Hyok Kim

            True indeed. Off topic, at least some gun writers have no idea of how firearms operate.

            There are some who wrote Walther P38 system is more accurate because barrel travel rearward in linear fashion! Some even wrote P38’s barrel is fixed!!!

            Even venerable Cooper one time wrote Luger was exceptionally accurate because the barrel is fixed. Not. Luger barrel does move even though extremely small distance.

    • Kivaari

      There is a Yugoslav article from about 30 years ago, that argued the 7.62mm NATO round was TOO violent. Yugoslav Army tests was done using FN ammo, which used a thinner jacket than the US military load. It was showing how superior the 7.62x54mmR, 7.62x39mm and 7.9x57mm in use by them left the target with less serious wounds. A commie claim that they used more humane bullets to kill people with. I’ve heard complaints the 7.62mm NATO did not work well. This was published in Wound Ballistics Review. This argument was around the use of the Sierra 168 gr. Match ammo, as used against Randy Weaver and a cop killer in Alaska. The article was pointing out how to improve the lethality by drilling a slightly larger hole in the OTM bullets. It would be easier to simply use hunting ammo, as it would work.

      • TR in his account of the Cuban campaign of the Spanish American War noted that the 7mm Mauser rounds were lethal if they hit in brain, heart, or spine, and that soldiers hit in other places recovered amazingly quickly.

        US 7.62×51 bullets use a thicker bronze jacket, and don’t deform much. German 7.62 bullets use a thin steel jacket, and at higher speeds will fragment.

  • Matthew Brennan

    I would suggest that when citing a primary source for your blurb, it would be appropriate to list the original authors, in this case Doc Dater of Gemtech fame and Jason Wong of the Firearms Law Group.

  • gunsandrockets

    Two very bad things about short 11″ barrel on an AR compared to a 20″ barrel, much greater muzzle blast and reduced reliability.

    IIRC, the whole reason for the 14.5″ barrel on the M-4 carbine was trying to find a fix for the reliability issues of the original shorty XM-177. 14.5″ was as short a barrel as they felt they could go with acceptable reliability.

    • I was under the impression that the 14.5″ barrel was as short as they could go and still mount an bayonet and GL.

      I mean, it took some troubleshooting but the Mk. 18 upper seems to work pretty well. I know the CAR-15s were fairly unreliable, though.

      • me ohmy

        I still like a lightweight 20″ upper..5.5 inches really isnt going to make THAT much difference..put a carbine slider on the buttstock your within inch of carbine OAL..
        one of my lightest builds is a classic triangular surplus M-16A1 carryhandle upper 1-12 with a carbine style lower..

        • gunsandrockets

          I may have to try that!

      • Kivaari

        Every serious book or article I’ve read on the CAR15 (XM177) had bad reviews regarding functioning. If I had a choice, which I do, I’d take a mid-length light weight barrel, with a good optic and BUIS system. Since I don’t have serious use (need = swearing in church) for anything at my advanced age. I did like the M16A1. Had the military improved the stock furniture (A2) replaced the aperture with a Daniels Defense A1.5 sight with a M1913 rail on just the top and half of the bottom it would be a great rifle. The M1913 hand guards invite adding too much gear and many lack heat shields.

        • Yes, the CAR-15 carbines were plagued by poor functioning. Colt still understood that system fairly poorly, and the relationship between gas port, buffer weight, and the functioning of the gun wasn’t as well understood then as it is now.

      • FWIW: You go as low as 12.5″ and still mount a legacy M203. The late M2 Corp. once offered this configuration as the M4N.

  • “It has already been documented that standard military issue M855 relies on fragmentation to inflict sufficient damage to the target’s tissues”

    Would you be so kind as to provide such documentation?

    One thing I’m unclear on regarding the arguments of the bigger caliber crowd is that M855 is supposed to have to rely on fragmentation to do damage to a target, but something like 7.62×39 does not. How is this so? In what way do the bullets perform differently? What sort of serious suggestion is there that the slightly wider hole has any measurable affect on the effectiveness of the shot?

    We’re talking about projectiles that cannot even make a clean round hole in brittle paper*; why will a 5.56mm round “just pass through” while a 7.62×39 or other round will “ruin a man’s day”?

    *To clarify what I mean by this, it’s often argued that .30 caliber holes are bigger than .22 caliber holes, and thus cause more damage and the target to bleed out faster. Well, alright, but if that’s so where’s the test demonstrating this? And how is it that .30 caliber rounds are supposed to punch neat .30 caliber holes in people and .22 caliber rounds are supposed to punch neat .22 caliber holes in people when they can’t even punch a neat hole in paper, instead stretching and bending the paper as they go through. So where’s the evidence, any evidence, that this theory of wounding is correct?

    On the other hand I have heaps of evidence that .22 caliber bullets will tumble more readily and generally use their energy much more effectively than larger caliber bullets, all else being equal. I have evidence that rifle velocity projectiles cause remote wounding, regardless of their caliber or energy levels. Where is the opposing evidence?

    • Kivaari

      The primary OLD AK round the Soviet M43 PS, steel core, is as long as the M14 147 gr. bullet. It is very stable. Having a boat tail design it slips right through. The flat based Yugo load is more lethal since it tumbles. Most of those designs where the bullet remains intact, tumble leaving a bi-lobed would channel with bullet coming to rest base forward. It is a desirable thing to have in a military bullet. Flat based bullets shed velocity and thus range faster than a boat tail.
      The only reason for using low drag bullets is to increase hitting ranges. The argument is it is better to hit the enemy at longer ranges, with a less lethal bullet, than to miss them at a closer range with a more lethal bullet. THAT is why we use OTM match bullets. The open tip match bullet even though it is a hollow point, doesn’t expand like a sporting bullet. Thus it is lawful in international combat. Civilian police in the US would be wise to use a good hunting bullet regardless of caliber. Ranges for domestic police are normally much less than in Iraq or Afghanistan. Think Randy Weaver. he was shot in the shoulder with a Federal 168 OTM Match King. It pokes a nice hole. A hunting bullet may have taken his arm off.

      • An excellent brief analysis of bullet design, Kivaari.

      • Center of pressure for a symmetrical airfoil is always around the 25% chord point. Move the CG further rearward it increases the torque to turn a yawed bullet. Think of a aluminium bullet with a tungsten plug in the back.

        Since flesh is ~1000 times as dense as air, spin stabilization required for air is much much less than that which would be effective in flesh or body fluids. Higher spin rates don’t really affect ball rounds, they are normally required for tracer rounds which tend to be longer to have as much mass (and thus similar trajectory) as ball rounds, but will diverge as drag of tracers is less.

        Rather than shooting mix of tracer and ball, and using tracers to guide 20% of your rounds to the target, better would be to shoot 100% dim tracer, with a compound that didn’t burn as fast or hot, giving longer tracer range, greater uniformity (since all rounds are tracers) and a trail that would be visible with IR goggles, but perhaps not with the naked eye.

        • Kivaari

          The RPM seemed to have a verifiable effect. I am going from the medical-ballistics studies done in the 1970-1990 era. Our army showed that the faster rate of twist did increase wounding ability. It was not very significant, but it showed the Swedes (and FN) in the quest to make a bullet that did NOT perform like the 55 gr. M193 was more humane. In the end, both bullets flying along, hitting medium denser than air, made nasty wounds as long as the bullet tumbled, and especially so if it broke apart.
          RMP will make a bullet vaporize.

  • Kivaari

    Well it was pretty well done, until I read Nathaniel’s comments. He makes some very good observations.

  • Kivaari

    Taking one between the eyes would probably really ruin a days adventure.

  • me ohmy

    andd.. in that time frame of that term being *so archaic* you have a massive amount of anti SPACE SHUTTLE DOORGUNNER swipes dontcha. I am still waiting there jumpy snot zed

  • Kivaari

    Sometimes velocity tests give inaccurate data because at some point the screen start measuring the muzzle gases. If no baffle is used, all of a sudden the gasses are moving faster than the bullet.

  • Kivaari

    The only thing wrong with the SKS is the reloading. Had it been first issued with a good magazine, I doubt the AK would have been develop. There are sheet metal variants of the SKS, done to lower production costs. But by then the AK was well advanced.

  • Kivaari

    If a bullet enters the body, it is more lethal than a bullet that doesn’t.

  • Jamie Clemons

    Wound channel less than lethal??? It is not the size of the wound channel that causes lethality it is the placement of the shot.

  • Kivaari

    Soviets needed more guns and continued to produce rifles and SMgs of any type. AVS, SVS, AVT. SVT, PPSh 41, PPS 43, 1895 Nagant, TT33, SKS45 (issued in ’44) M91/30 and more. The amount of floor space and steel used to produce the SMGs was a significant issue. Machine time coupled with steel chips (left by machining) and square meters of shop space were studied to a great degree. Desperation led to lots of weapons work.
    Soviets had poor tactics and wasted men, but had a large pool of new recruits. Germany always bit off too much to chew. The arrogance of Germans brought them nothing but grief. Except for killing Jews and Slavs was more important than gathering living space. Greed beat out common sense and a business contract approach to supply and demand. Socialism by Germans done to Obama-like Cash for Clunkers and Green cars, drove Germany to near extinction.

  • 55 grain is M193, not SS 109. SS109 is the same as M855.

  • One can fold the suppressor back along the barrel, so the gasses vent into a closed chamber, to be released at lower pressure after the bullet passes out.

    The other point to make is a bullpup configuration permits longer barrel with shorter rifle, but extra care has to be taken to get a good trigger.

    The bullpup rifle has less variation in the way the rifle swings as ammunition is depleted, which could help training. There could also be less tendency to monopod off the magazine.

    Some folks like top mounted magazines: much less tendency to monopod, increased reliability and less restriction on magazine length.

    • Kivaari

      Future enemies may have night vision devices as good as our. The IR tracer going up against Taliban fighters in night shoots would be valuable. Having NVDs on, to see those daylight tracers, would be a drag, especially in daylight hours. Bullpup rifles have never impressed me from several aspects. They are club-like in handling. MOST are not ambidextrous and need down time to convert one side to another. The FN2000 and P90 handle spent brass OK. Based on written reviews it sounds as if the FN2000 has very POOR accuracy. If the FN functions, becomes accurate, has easy reloading and doesn’t dump all its weight into the buttstock there is potential. I have never shot any of the modern bullpup rifles, just handled them, and hated them.
      I have three AR-type rifles left. An M4 with Mk4 Leupold, a 20″ HBAR (awaiting optics) and my favorite is a BFI lower with BCM 16″ LW mid-length upper, using a Daniels Defense A1,5 sight. I’d feel happy with an M16A1, but at $20,000 I will not buy one. An M16A1 costs as much as my first stick built house with an ocean view That was 2/3rds of a lifetime ago.

  • In what way is that a strawman argument? Recall that this is a direct quote from the article:

    “M855 bullets traveling below 2,500 fps when impacting a target will not produce a lethal wound channel.”

    • AlDeLarge

      Try quoting me “suggesting anything less powerful than an M1 Carbine is ineffective.”

      • I don’t feel I should have to walk you through the conversation, but here you go:

        You asked this question:

        “Why are you saying they’re wrong, while saying the same thing?”

        I answered you:

        “The idea that below 2,500 ft/s, 5.56 magically stops being lethal is what I am contesting. Or are you suggesting anything less powerful than an M1 Carbine is ineffective?”

        The second sentence in my response is a question, asked to identify why you sound confused. You’re making a mistake in identifying this as an argument; it’s just a question. You’re free to answer it however you want.

        • AlDeLarge

          I don’t know why you’re so confused. If you wanted to refute the idea that it wasn’t lethal below a certain velocity, your example should’ve been about the lower velocity, not the same velocity. All you did was agree that it’s lethal at their lower limit. Pretending I said things I didn’t doesn’t help, either.

          • I never pretended that you said things you didn’t. I asked you to clarify what you were saying. Those are two different things.

            Firstly, a .22 LR is lethal, so it doesn’t take much, if any, refutation to counter this statement:

            “M855 bullets traveling below 2,500 fps when impacting a target will not produce a lethal wound channel.”

            One can further understand that bullets lose velocity as they travel downrange. If I compared a 62gr bullet moving at 2,500 ft/s to a 110gr bullet moving at 1,900 ft/s, the latter being regarded as a reasonable round for use under 200 yards, you can infer that a 62gr bullet impacting at a lower velocity than 2,500 ft/s may also be effective.

            With this comparison, we can whip out our ballistic calculators to see that an M1 Carbine (assuming a muzzle velocity of 1,900 ft/s) produces 475 J of energy at 200m. A 62gr M855 projectile fired at 2,500 ft/s produces approximately the same energy at 320m.

            The FMJ round of the M1 Carbine doesn’t do anything exotic when it hits a target; it doesn’t tumble, fragment, or expand. Given this, the argument that at impact velocities below 2,500 ft/s the M855 round “isn’t lethal” really sounds ridiculous, doesn’t it?

          • AlDeLarge

            Saying it again doesn’t change anything. You’re still saying it’s lethal at less than that velocity because it’s lethal at that velocity.

            It’s like saying 5’0″ is tall enough to ride the roller coaster, because 5’6″ is tall enough.

          • Al, saying what you’ve just said makes the implicit argument that the M1 Carbine is not lethal except at kissing distances. I get the impression that you didn’t intend to make this argument. Is that correct?

          • AlDeLarge

            I get the impression you have no interest in addressing anything I actually said.

          • I have taken a lot of time out of my day to address what you’ve said.

          • Hyok Kim

            I hope you getting paid for this. One reason I no longer go to usual gun forums.

          • I get paid to write the articles, but not for commenting.

          • AlDeLarge

            You may have spent a lot of time avoiding my point and pretending I said things I didn’t, but you haven’t addressed what I have said. If you’re going to say a limit is too high, don’t use an example at the limit you’re refuting. Use an example below the limit.

          • .30 Carbine headed downrange is below the limit, Al.

  • Hyok Kim

    “5. While the effects of energy deposition are not as well understood as I should like them to be, energy deposition with regards to rifle projectiles is very important with regards to terminal effect.” – Nathaniel F.

    “Didn’t you say energy and momentum were irrelevant?” – AlDeLarge

    “…but I forgot about your strawman arguments.” – AlDeLarge

    http://en.wikipedia.org/wiki/Straw_man

    http://en.wikipedia.org/wiki/Hypocrisy

    • AlDeLarge

      He said it before, in articles he wrote:
      Energy: Don’t Sweat It!
      and
      Momentum Has Nothing to Do With Stopping Power

      Now he’s saying energy is important. Hence the question “Didn’t you say energy and momentum were irrelevant?”

      It’s not a strawman, and I’m not a hypocrite.

      • Hyok Kim

        I’m sorry. I didn’t read the articles you mention.

        I clicked the link you provided, but it’s not there.

      • Hyok Kim

        “A further example of this can be found in another BrassFetcher video, comparing different carbine cartridges with each other. Despite the larger caliber cartridges’ greater muzzle energy than 5.56mm, for the first half of projectile travel, energy deposition and temporary cavitation look nearly identical. This early segment of travel is the most important when discussing terminal effectiveness against human foes:” – Nathaniel F.

        My dear AlDeLarge,

        It’s obvious Nathaniel F. is saying from the article you mentioned, he’s not saying energy is irrelevant.

        He’s saying that beyond a certain threshold, more muzzle energy doesn’t result in more energy being dumped on the human body aka ‘stopping power’, another word, this obsession with more energy at any cost result in waste of that energy for self-defense purpose.

        – See more at: http://www.thefirearmblog.com/blog/2014/08/08/energy-dont-sweat/#sthash.MmFS3Qqc.dpuf