Armor Development Group INSULON M4 Thermal Shroud

The military is developing an improved version of the M4 Carbine with a heavier profile barrel to allow a higher rate of sustained fire in emergency situations like, for example, the Battle of Wanat where M4 Carbines began failing after long periods of sustained fire. According to The Ground Precautionary Message ACALA #97-031, the M16 and M4 Carbine can only sustain 12-15 rounds per minute over long periods of time. A heavy barrel will help, but that will not prevent the Carbine’s gas tube from overheating and eventually bursting, leaving the rifle unable to cycle its action. The video below demonstrates …

The Armor Development Group, a military and law enforcement research and product development organization, has developed an insulated gas tube for the M4 Carbine to keep barrel heat away from it. Judging from the thermal photos they sent us, it is very effective …








We will be testing the prototype in the near future and will report back.

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • bbmg

    I’m missing some of the logic here. Is the biggest source of heat for the gas tube radiated barrel heat, or the gas which itself is passing through the tube? Doesn’t insulating the tube mean that this latter heat is retained?

    • Giolli Joker

      My same doubts… I’d rather see useful a flat insulating shield between barrel and tube (a strip of that INSULON (ceramic?), maybe) and a new tube with cooling fins, or in (expensive) Inconel that can better withstand high temperatures.
      Anyway, if that’s the way their following, I can assume they have more data than me in their hands to support their choice.
      (Any comparative test on this issue with a piston driven AR?)

      • bbmg

        Good ideas – any why not throw in some Lewis/Pecheneg style forced air cooling too 🙂 no moving parts and simple to engineer.

    • Tenacious221

      I suspect this is a coating on the inside of the gas tube.

      • raz-0

        Well, you can see it is an external shroud in the first picture.

        Given that the sustained fire rate for the platform is greater than 12-15 RMP, but the requirement is only for something like 2 minutes of full auto fire at that high rate, I’m guessing their concern is very high barrel temperatures heat soaking the gas tube so it doesn’t get to cool off and then fails under less strenuous but longer duration use.

        With the coating, it probably fails at the same point under full auto fire, or possibly earlier, although the shroud may prevent sagging which is where it all goes sideways.

  • Ghostalker

    Certainly is odd. Also, why full auto fire for the bare tube and ‘rapid semi’ for the coated tube?

    • bbmg

      Yup… also, if the tube is insulated, it is obviously going to appear cooler on the thermal camera – what about the heat *inside* the tube?

  • Alex

    “The military is developing an improved version of the M4 Carbine with a heavier profile barrel to allow a higher rate of sustained fire in emergency situations”

    Yea it’s called the M4A1.

    • Anonymoose

      *improved M4A1
      They’ve modified buffers, barrels, and now this with the M4A1. They haven’t changed the designations since 1994 despite a lot of changes from the cut-down M16A2s they started as.

  • Tenacious221

    The coating must be on the inside. Otherwise how do you keep the gasses in the tube from heating it up?

    • bbmg

      The gasses in the tube *are* hot – it’s gas which is bled off from the barrel. Therefore, insulating this tube makes it more difficult for this heat to escape.

  • Zach Haag

    Whoever carries this much ammo into combat and uses it this fast is a complete dumbass… how about you just switch it to semi and let the SAW do its job!

    • Rev

      Its for troops in contact at a FOB or COP where theyll have ammo reloaded and fed to them. In the end theyll shoot a whole helluva lot more than they could carry. Also, at the battle of Wanat the insurgents knocked out their .50s, 240s and other fixed guns with RPGs and other heavy weapons so all the troops had were their M4s.

      • Joshua

        Battle of Kamdesh(similar fight, lasted longer, went black on numerous rounds, soldiers fired more than 40 mags through their M4’s and only one M2 failed in the fight thanks to taking an RPG)……Go look it up. Also Wanat was not as bad as the media made it, AAR’s showed only 4 M4’s failed in that fight and one took a bullet to the receiver.

        I’m sure we have all heard the whole my barrel turned white hot, did you know that is not even possible?

  • Edgar

    Think this is not really needed. Wanat showed poor army training and lack of support fire. So the first BIG factor is no spraying bullets and to not use a rifle as a SAW no matter if its a DI or Piston gun they all would have failed at Wanat. Fell the barrel and buffer needed improvements more than this.

    • Joshua

      Check out what happened at Keating in the battle of Kamdesh. Their fight was identical to Wanats, it lasted longer, they went black on numerous rounds, and multiple documented soldiers fired 40-50 mags through their M4’s.

      At the end of the day only on weapon suffered any failures of any kind and it was a M2 that was hit by a RPG.

    • johan

      Not really. I think soldiers relying on their rifles to fill the SAW role will become more common. Soldiers in western nations are becoming more expensive to train, equip and sustain in the field, which is why there is less of them at any one time in one area. Western soldiers will increasingly be outnumbered by their enemy in the field.

    • joe smith

      Um, look at the replacement for the SAW. 😉

  • Joshua

    I don’t see the point, gas tube melting is really not an issue in the real world. Colts failed around the 850 mark of non stop full auto, no one generally carries that many mags, and even if they did no one will dump everything they have in full auto over a span of 4 minutes.

    It really is a non issue when it comes to actual combat.

    • MattInTheCouv

      in the heat of an iraqi summer, in a firebase defensive fighting position, with ammo cans full of loaded magazines sitting right beside you, trying to repel an assault by countless bad guys mostly all hopped up on stuff to not make them mind getting shot so much… you CAN burn through an ungodly amount of ammo, i hear.

      • Joshua

        Let me guess your talking about Wanat……God why can’t people ever look into any other battles, I mean if your only source of info is going to be what the media tells you do some research.

        Wanat was not a battle that can be used to say what does and does not need to be fixed with a weapons system. Trust me the vast majority never have an issue with the gas tube overheating, I know I never did and I never knew anyone that did.

        You should go and compare the Battle of Wanat to the Battle of Kamdesh. The attack on COP Keating lasted longer than Wanat, the soldiers went black on numerous calibers during the battle, they killed more insurgents than the soldiers at Wanat, they had just as many casualties and wounded as Wanat did, multiple soldiers fired more than 40 magazines through their M4’s, and yet with all of that the only reported failure of the soldiers weapons came from a M2 that ate an RPG.

        But I wouldn’t expect the majority to know this as the media never reported on it, mainly because none of the soldiers came out crying about their barrels magically becoming white hot(something not even possible) or how their weapons were having issues left and right, because you know having soldiers say they expended more than 40 magazines through their M4 and never once having any issues with any weapons they had with them wouldn’t make for a good news show.

  • patrickiv

    Piston anyone? The gas tube is being heated by the gas passing through it, not from heat radiating off of the barrel. The insulator will shield the polymer hand guard from the gas tube’s heat, but it will keep the heat within the gas tube. This will make the gas tube hotter than if there was no insulation and lead to faster failure. Their thermal images fail to show the actual temperature of the gas tube underneath the insulation.

    • José Pulido

      The point of the AR-15 at all is to be lightweight. Adding a piston system defies that purpose.

      • Georgiaboy61

        Saving weight is OK – up to a point. The grunt going into battle needs a weapon that he can count on no matter what. That goes double for sustained fire weapons, which should be over-engineered and soldier-proof. Not saying we should slavishly copy the past – but think WWI, WWII and Korean War era weapons. Speaking personally, I’d hump the extra weight in order to have something I know will work when the you-know-what hits the fan. The M-16/AR-15 design has gone as far as it can be taken; our designers need to start fresh. And when one designs a firearm, one starts with the round it will fire. The 5.56mm isn’t up to the job. Something in the range of .270 caliber or larger should be considered ~ or if you prefer metric, something in 6.5mm range (.65cm).

        • José Pulido

          Cool story, bro, but maybe you shouldn’t read so much Guns And Ammo/company stuff when you’re trying to develop an informed opinion.

          Saving weight is not OK. It’s the ONLY goal that comes immediately after “it works, and we can afford it.”

          You say YOU’D hump the extra weight, but who in the HELL are you? If you’re even in the military, I sure as shit know you’re a POG, since only a POG would ever declare that he’d “gladly” hump more weight.

          The AR-15 design has hit an impasse you say?

          The H&K416 AR-15 pattern has ~240 malfunctions in 60,000 an artificial sandstorm, while the FN/Colt M4/M4A1 pattern has ~300, and the AR-18 pattern SCAR16 has ~220 in the same test.

          The 75th Ranger Regiment wasn’t fussy about ditching the contract for the fancy new SCAR16 to return to the Mk18 because they couldn’t report any tangible advantage to the SCAR16 that could justify the weight and cost.

          An HK416 with 14.5″ barrel weighs 7.7lbs.
          A SCAR16 with 14″ barrel weighs 7.2lbs.
          A Colt/FN M4 weighs 6.3lbs, depending how it’s set up.

          And who are “our designers?” Are you referring to armorers? They don’t design squat. Design is mostly performed by private industry, as it’s always been.

          Funny how you say the 5.56NATO is broken, yet the DEVGRU operators who captured that Al Shabbab member in Somalia didn’t leave behind 6.8spc or 6.5grendel(drool, bro), they left behind Mk318 5.56NATO, regardless of working alone(meaning it wasn’t for the purpose of sheer logistics.)

          Even if the 5.56NATO is inadequate from 10″ barrels as is likely to become standard, new powders and projectiles should solve this problem, as they are doing with the 13″ barreled SCAR17. Upwards of 2,800fps from medium weight 7.62NATO medium weight projectiles, and they didn’t even have to cower and say “We didn’t expect barrels to get shorter, let’s quit and see if we can get ALL OF NATO to adopt a cartridge of the USA’s choice again!”

          You talk of innovation, yet your only response to perceived inadequacies arising in the cartridge we use is “replace it.” I doubt you’re even a POG because you can’t possibly be so ignorant of logistics, then again, people have proven me wrong on bigger things.

          • Esh325

            It can be difficult to make any astound conclusions from such tests when people of the outside don’t know the conditions of the tests in question, or whether they were fair. I don’t know how SF procure their equipment, but I imagine they some times have to use what’s available to them. 6.8’s aren’t often available to them it seems. If I recall correctly, the 6.8 was developed by SF in response to percieved issues with the 5.56×45. Whether or not the 5.56×45 has issues is very debatable.

          • José Pulido

            If they were having issues procuring the weapons of their choice, they wouldn’t be shooting Mk318. I find it hard to believe they were using 5.56NATO as a last resort.

            Ask any rifleman about Mk318 and most won’t even know what it is.

            The fact that they left behind an emag and 4.6 MP7 mag further pushes my thought into the realm of “they don’t seem very limited.”

          • Esh325

            It’s still easier to issue a different loading of the 5.56×45 than to issue a whole new caliber. That’s only one incident.

          • José Pulido

            It’s only one incident, but it’s a real incident.

            I didn’t cherry pick it to try to prove something, it’s just the most recent incident where stuff was left behind that I know about.

            If they can get ahold of MP7s and emags, they obviously weren’t plagued by shortages and old gear, and being JSOC, I find it hard to believe the only reason they didn’t opt for HK416s running 6.8spc is because it was slightly easier to get ahold of unicorn ammo for a standard rifle.

            People are losing steam fast on the “glorious” 6.8spc. Why? Because they declared 5.56nato invalid before they even tried to update it. Once they did, it quickly became apparent that the marginal improvement given by 6.8spc is just that… marginal, with a plethora of problems associated with its use.

      • patrickiv

        How much weight does a piston system add? Please provide a source.

        • DalekVal

          He doesn’t have one, it just more AR-15 fanboy bs like Lance.

          • José Pulido

            “Fanboy bs” to you is reality to anyone who knows what they’re talking about. do I think the AR-15 is the greatest thing to flake off of John Browning’s divine hand? Not at all. Do I think it’s perfect? Nope.
            Do I know it works, and is far more advantageous to keep, than to blow our entire military’s budget on rifles with marginally better performance in specific areas, with new problems in others? Yes.

            The only real mechanical difference between a SCAR’s operating system and an AR-18’s is that the SCAR system has the operating rod built into the carrier, while the original AR-18 didn’t.(a closer derivative of the AR-18’s would be the ACR, which keeps the oprod separate.)
            Everything else is small trivialities, such as going with a single spring/guide rod rather than a set of two, modifying the bolt head to work with the rather lazily designed bolt catch, etc.

            The Tavor has a notably different bolt head, but the principle and basic form is all completely derivative of the AR-18 notwithstanding the longstroke gas system. It’s actually a very thoughtful and creative take on the platform.

            To claim that the SCAR is an independent design not based on the AR-18 is either ignorance, or willful deception. You might as well go on to tell me how the Browning Hi-Power wasn’t designed by Browning because he originally designed it to be striker fired, and never finished the magazine.

            I’ve never played Call of Duty in my life, so I can’t say that I don’t use their jargon.

            You sound like the type of person who probably trolls videos where people use AR-15 derivatives saying “ur gun jammed bc it wasnt a AK, faggot” and things of the like.

          • DalekVal

            Nope it still is Fanboy BS To call the Scar Tavor’s weapon based on the AR-18. I’ve seen the internals of the Tavor and Scar and their nothing like the AR-18, except for being piston driven. Stoner’s Ar-18 system isn’t as revolutionary as you think it is. If it was the Army would have purchased it, nor would have had the Brits ask H&K to fix the L85, the G-36 internals wouldn’t a heating problem, and the the JSDF would have choose a better weapon system then the Howa Type 89, which needed flied mods to work in Afghanistan. Nor would the HK-416 jam(G36 upper, AR lower) in cold weather. The SCAR and Tavor wold also have those problems but its over stretchering that you think all piston driven systems are based on Stoner’s work.
            You don’t even have proof or links to verify these outrageous claims.
            If we go by your Stoner fanboy logic the SG550 , ARX 160 , and CZ-805 are also based on the Ar-18 which also isn’t true.
            As much as you would love the 18 to be so, its just isn’t the new AK-47 you claim it is.

            The ICC was rigged in favor Colt because they paid off the Army to stop it. Continuing the program would have not wasted tax payer money like the Army is known to do with an obsolete weapon system. They purposely sabotaged it with “new ammo” just made specifically for the M4, just so Colt keeps their billion dollar contract.

            So Russains civies love crappy obsolete weapons instead of decent firearms? When they can have superior Euro-stuff from a country over the AR?
            I know you love your “Stoner gun systems” but that’s another dubious claim of yours.

            The new model AK’s aren’t even AK’s in the modern sense any more. As their just the AEK-971 in a an AK shell. Which is more factual about your fan-boyish claims about the Tavor and SCAR.

            It’s a waste of money to continue using a piece of junk chosen by Air force bomber jocks because they need a cheap system to project their planes. It was never meant to fully replace the M14, and just a stop gap solution and we are still using that same half assed choice. Our soldiers are dying and suffering because the Generals love themselves some tax payer money instead of real innovation.
            The AR-15 is only in service now because the Army bidrigs their contracts, like the Air Force did for Lockheed for the F-22 and F-35. If big Army has their way, they would replaced “the crapping where you eat” system with every other gun in their inventory.

            The same reason is why the Marines choose a fancy looking 1911 instead of a system that can actually compete with the Glock 21 and PX4. More bullets per mag, less weight, more durable, but some how an inferior gun with a shorter barrel came out on top. Something that 45 acp benefits from, derptastic move for the favored boys of the Force Recon.
            You can put all the bells and whistles you want on a piece of crap buts its still a piece of crap.

            You make the Hi-Power sound like a weapon designed by committee. Which is why most smart Armed Forces are replacing it. However that is what the Army does with the M4 when ever a problem crops up instead being a superior carbine. Just add new stuff to an already over engineered system and robbing tax payers.That is “Private Industry” for you, fancy bells and whistles but no real improvement over what already exists. I know you love hyping the Stoner systems very much but the AR-15 isn’t an enduring design you lot pretend it is.

            And you sounding like a mindless fan boy from the Heritage foundation website who jacks off into his “Stoner-man system gun” and gets butt hurt every time the Stoner system is bashed.

            I prefer non AK piston systems because unlike the AR systems they actually work instead of locking up like Windows 98. Reliability is a lot more impotent than an expensive, lightweight lemon known as the AR-15 and AR-18. Or as I call it them the gun equivalents of the F-35.

          • José Pulido

            You sound like a complete jackass.

            I specifically noted that the piston system used in the Tavor is unrelated to that of the standard AR-18 pattern.

            Long stroke is not the same thing as short stroke. Understand that? “Piston” doesn’t mean shit in the real world. The AR-15’s gas key itself is an inside out piston, does that make it short stroke? NOPE. You’re trying to group together all things “piston” and it just doesn’t work, cowboy.

            The Army doesn’t purchase things based on them being “revolutionary”, it purchases them based on NEED/bureaucracy. It’s always been that way from the Hessians running smoothbores while rifles were around, to the US Army running single shot breech loaders while full power leverguns were available. They don’t need something, they don’t buy it. That’s how it is. The Army is not a person, it’s a machine, and it can’t survive by spending money willy-nilly.

            Now that the Army has a modern rifle that is on par with any other(the only current shortcoming being that they need to add an adjustable gas system.) they’re even less likely to adopt a new one, since they not only don’t need it, but they’d be hard pressed to gain any advantage from it.

            Your Type-89 of the JSDF example just shows how big of an ignorant moron you are, since the Type-89 is LITERALLY an AR-18 modified to fit Japanese manufacturing processes and preferences. Howa was practically the only company licensed to produce the AR-18 except for Sterling in the UK.

            Japan has never seen real war since WWII, and as a result, the Type-89 is a ridiculously foolishly executed rifle. Its horrible reputation is not surprising in the least, even with what little I know about it.(I’ve never seen one personally, and hope I never do.)
            For example, the Japanese found it was easier to just make a bigger magazine well rather than broach a properly sized one to make inserting magazines more fool-proof. It bit them in the ass. Their pathetic excuse of the AR-18(here, literally an AR-18) is just a skip, a hop, and a jump away from being worse than a Khyber Pass-type deal. Claiming the Type-89 is representative of the AR-18 is probably worse than claiming that Khyber Pass AKs are representative of the AK platform.

            The current issue SIG 550 series of rifles uses a blatant AK pattern bolt carrier, coupled with a heavily modified gas system. You’re not cute.

            I’m not familiar with the ARX-160(what American is?) nor with the CZ-805(yeah I’ve totally tried one at my local shop because there are SOOO many in the country, and specs for the internals are available online), so I couldn’t tell you if they’re orphan designs or follow a certain pattern.

            You think it’s reasonable for the British Army to trash their rifles instead of try to fix them when they had reliability issues? You must be 12 years old, brony. All rifles have reliability issues starting out. The AR-15 platform jammed like raspberries, the AK-47 snapped at the front trunnion. It’s normal.

            The old “Colt cheated!” excuse doesn’t work out too well anymore.
            LMT produces Mk18 uppers, KAC produces M4 rails, DD produces Mk18/M4A1 rails(as does KAC in small numbers), FNH produces all but all replacement/upgrade bolt carriers, and Colt now has to share their contract for complete rifles with FNH(producers of the SCAR series.)

            Sabotaged by Colt, who made sure “special ammo” was used that could only function in the M4? Really, now? The competing rifles all used the same ammo, and there wasn’t anything special about the M4s used, so what you’re telling me is that the M4 can run on ammo that the others can’t? While I KNOW that that is complete BS that you just pulled from your anus, it wouldn’t even begin to be a negative. A gun should be able to run anything. Unless they were weird subsonics, there’s no reason the guns shouldn’t have been able to run them(if what you say was true, which it’s not.)

            You have no clue what I’m talking about. I’m talking about the reality that most of the issues with weapons systems are not the operating mechanisms, it’s ergonomics and modularity. When your system is so outdated that you can’t update it, you jump ship. When your system can be updated to a satisfactory level with a few commercial products, you polish it off and keep moving forward.

            The Russians are obviously trying to adopt new(and not so new) technology such as NODs, simple flashlights on their rifles, and optics. They have no practical ways to attach anything to their rifles, except optics(sort of), because when a new rail system or other practical devise is devised, it’s not going to be released to the public, where the public will hate it but still want it and demand a better version, and actually have the option of going with a better version from a competing company, forcing more and more companies to compete.
            This is why Russian special forces actually go with American tacticool crap, because they don’t have anything better. Their rifles work. If your rifle works, there’s no need to replace it the operating mechanism, if it can’t do what you need(i.e. hold an IR laser) there’s probably a way you can you can get one on there.

            A more modern operating mechanism will never make a weapon more effective if it already works. The cartridge it fires will remain the same. Improvements in weight/ergonomics/modularity are actually advantageous.

            The opposite side of the spectrum is the USA, where KAC started with their shitty rail for SOCOM, and the civilian market kept pushing that forward until they had a million and 1 rail systems getting lighter, thinner, and more comfortable. The most recent and more ideal rails being the Keymod systems which eliminate the need for picattiny entirely.

            I never claimed the AEK was an AK. The AEK will not be adopted, since it is far too expensive to produce, as is the AN-94.
            The AK-74M will remain in service until it is replaced with the AK-12. The furthest thing from the AK pattern that may adopted in the future will be the AK-107, which even with its heavily modified gas system, still uses a Khalashnikov-derived bolt carrier group.

            The SCAR series uses an AR-18 pattern bolt carrier, with the operating rod built into it. The bolt carrier of the Tavor is strikingly similar to the SCAR’s, which you’d know if you’d bother to look it up.
            Our boys aren’t getting killed by their AR-15s jamming anymore.
            If you’d actually served, you’d know that, and no, just because you have a cousin whose friend has a brother who was a field wireman, doesn’t mean you have half a clue what you’re talking about.

            The biggest problem associated with the AR-15 pattern is the magazine(the same magazine used in the SCAR, ACR, C8/C7 rifles, HK416, SA80 patterns, etc.) This problem is relieved by adding an anti-tilt follower, and solved by using polymer magazines instead of the rather fragile aluminum.

            The M14 was past its time anyhow. Just because something “wasn’t supposed to happen” doesn’t mean it was a bad move.

            If we adopt the nicest and shiniest rifle out now, morons like you will be complaining in 10 years when something shinier comes along, and holler “obsolescence” when Army/military R&D who know what they’re doing choose to update the system instead of replacing it.

            The AR-15 is in service now because it works, the troops love it, there’s infinite possibilities for modification, and the only thing wrong with it is that it’s annoying to clean when you get around to it.
            Again, get it through your head, our soldiers aren’t dying because of it, and if you consider having to scrub the entire bolt carrier group instead of just the piston/gas block “suffering,” then you should probably stay out of the Army, it’s not for you.

            Force Recon chose the updated 1911 for whatever reasons they had. They love those things. Marines are generally issued M9A1s with 15 or 17 round magazines. The new 1911 will probably be issued to MPs, and other non-combat boys.

            Force Recon has pretty much always used in-house built 1911s likely because they’re faster shooting, easier to make hits with, and they just like it. They’re a small group, and get to do what they want.

            “bells and whistles” is what gives soldiers the advantage on the battlefield, and keeps them alive. A lighter gun means they can move faster, which is another advantage.

            Problems with replacing the AR-15 system include: heavier gun, the Army can no longer afford decent “bells and whistles”, and the Army has to make budget cuts in places such as body armor, camouflage, etc, but HEY, at least now they’ll have a gun that isn’t a “piece of crap,” even though you know, it’s heavier, bulkier, and doesn’t do anything the previous gun didn’t do.

            “Over-engineered”… what? I don’t see how that’s possible. More engineering means more thought, meaning a better system.
            I assume you mean it has too many parts, which it in all truthfulness does not, since it was specifically designed to have as few parts as possible, even replacing the piston/oprod/spring cups/etc. with this magical thing called a “gas tube” that weighs practically nothing and doesn’t even move.

            There are definite shortcomings, particularly my biggest pet peeve being the firing pin retaining pin being removable… and existing. Beyond that It’s quite rudimentary compared to other systems.

            No real improvement from “fancy bells and whistles?” The M4’s rail, while now seen as blocky, annoying, and heavy, which it is, and needs replacement, allows for the attachment of an IR laser, which allows soldiers to aim their rifles in the dark without having to be stuck looking through a dedicated NOD mounted on their rifle.
            Red dots/scopes allow for drastically increased capability for quickly returning fire/delivering follow up shots, increasing the maximum engagement distances of the rifle, and allowing for observation and spotting…. things that can and do keep soldiers alive more often.

            Private industry can take something like the Mk18’s Daniel Defense rail system, and spit out something like Noveske’s NSR 9, which is completely smooth on 3 sides so it won’t snag, weighs practically half as much, and is around a quarter of an inch shy of being half as thick.

            I’ve never had to/had the pleasure of being issued a rifle with a DD rail, but if I did, I wouldn’t mind being issued a rail system that was less bulky/snaggy, lighter, and more comfortable. It’s not as though boys are only carrying their rifles to the range to play with. That weight is held up by nothing but spine and knee. Fumbling with bulk/legos-tree-branch-feeling rails and not fumbling with bulk/lego— rails can make the difference.

            You praise new operating systems yet disdain new rail systems and advancements to existing systems. Pity.

            Nearly ALL weapons are “designed by a committee.” A lead engineer may head the project and direct the actions of their team, but unless the designer’s name is “John Moses Browning,” they are constantly bouncing ideas back and forth and solving problems with their team members.

            The Glock is no different from the Hi-power in practice, except the Hi-power has a manual safety. A polymer gun would be superior IMO just because it’s lighter, but they’re not free, and boys aren’t kind to things they don’t own.

            You should look up words before you use them. “Impotent” is not the same thing as “important.”

            The AR-15 will work in any environment you’ll ever actually encounter. The AR-15 is far cheaper to produce than any rifle that that ever competed against it in closed trials(the XM8 wasn’t adopted because the replacement was supposed to match or best the AR-15 in weight, and reliability while being cheaper to produce, which it could not do.)

        • José Pulido

          My source for the controlled failure rates is the 2007 closed competition results released by Army R&D. I don’t recall the actual article, but it’s popular enough to find.

          I’m not going to run out and and buy/borrow an MR556 to measure the weight of the gas block/piston/operating rod/springs/miscellaneous parts and compare them to the weight of a gas block/tube, but the difference is there.

          For a “real-world” comparison, a Colt M4(with those shitty KAC rails, carry handle sight, and its namesake profile barrel) is supposed to weigh around 6.3lbs. I can’t vouch for the accuracy of this commonly stated weight. I’ve only ever seen a couple of folks running those sights outside of basic, so how often they’re actually used outside of maybe Reserves is anyone’s guess.

          An M6-SL piston AR-15 from LWRC with a pencil barrel, Magpul MOE polymer handguards, and DD A1.5 rear sight is listed at 6.4lbs.

          You can have a piston AR-15 just as light as a DI one, you’ll just have to make compromises. The AR-15 was originally engineered specifically to eliminate the piston/oprod design, so adding one rather than going to a system designed around the oprod/piston design would be more beneficial.

  • Hunter57dor

    or, instead of squandering the tax payers money, they can buy something other than the AR platform, driven by a piston, which has been proven time and time again to work.

    • RickH


  • Michael

    Sounds like a spay and pray. controlled burst may have been more effective, would have prevented the guns from overheating.
    Do the piston guns overheat?

  • Alex Nicolin

    Why not replace it with a piston?

  • nadnerbus

    Gas tubes usually fail when they get so hot the steel sags and then the carrier key strikes the tube inside the receiver and bends it into a U shape, right? Would simple aluminum or steel struts that slip over the tube and rest on the barrel prevent or postpone that failure, or is the temperature already so high that it will end up blowing out or melting completely? I know that isn’t free float tactical and all, but for a rack grade rifle it might be good enough.

  • Tumbleweed

    Better alloy steel tube would help. Is it really effective to fire hundreds of rounds full auto at one time?

  • Christopher

    Leave it to big Army to waste tax payer money on a problem that already has a solution. Going gas piston or buying a new weapon system all together.

  • MZupcak

    Or you can install a short-stroke gas piston like HK or LWRC.

    Or you can replace the M4 with a more reliable rifle that can handle longer periods of sustained fire.

    I admit I am not a soldier, but if I had to go into battle tomorrow, the M4 carbine is one of the LAST 5.56x45mm weapons I’d choose. The fact is that there are more rugged and reliable 5.56 rifles out there and we don’t have an excuse for not equipping our soldiers with them. Compared to what our military spends on drones, aircraft carriers, etc., a couple hundred thousand rifles is a drop in a bucket. Give the M4 carbines to Iraqi and Afghan “troops”.

  • Blake

    Am I the only person that wonders why, with the US’s astronomical military budget these guys on the ground don’t get more close air support in situations like this? The Taliban certainly have RPGs but surely they’re not running around with SA-7s or Stingers (or know how to use them)…

    • DalekVal

      It’s because the fighter jock generals hate the job of CAS.

  • Paul Smith

    I’m not sure if the Marines, Navy or Air Force have M4s that are full auto, but the Army doesn’t use them now. The regular army now only has M4 rifles that are either semiauto or three round burst. The only 5.56mm rifle in use by the regular Army that fires full auto is the SAW. Therefore this test is flawed. Kinda useless.

  • joe smith

    So why not just switch to a gas piston ? Problem solved.

    • José Pulido

      Well firstly, because this problem doesn’t actually exist, and secondly, because that would bring its own set of problems to the system we’ve been polishing for over half a decade(and many would say we’re getting close to mastering.)

      It was designed specifically to eliminate the piston/oprod system.

  • José Pulido

    Company trying to capitalize on a problem that doesn’t exist. The gas has no chance to expand in the gas tube, so it will not burst. If this theory of gas expanding before it reaches its designed and intended destination was true, then piston guns would be plagued with pistons shooting out of guns, and oprods ramming into/destroying receivers like arrows shot from potato guns. Nope.

    Easier solution to the supposed problem is to just use an inconel tube or coat the inside with the magical heat-resistant space-polymer.

    • Paladin

      99% of gas tube failures in AR15 platforms are not due to bursting. The gas tube softens with heat, droops down out of alignment with the gas key, and then the bolt ramming home pushes the end of the gas tube out of the receiver and bending the portion under the handguard.

      Also, pressurized gas exerts outwards force everywhere all the time. Claiming that it magically does not expand until it enters the BCG is blowing it out your fourth point of contact. The issue of gas tubes bursting is because, again, the softening of the metal as it heats up. As the metal softens it’s resistance to pressure weakens. Piston systems generally do not encounter these problems as they have thicker walls in high pressure areas providing higher tolerances and more mass to absorb the heat.

      • José Pulido

        99% of gas tube failures do not exist. I have seen people do beyond-stupid things to their rifles without failure. I’ve only ever seen them fail in youtube videos for the sake of demonstrating deliberate destruction of the rifle.

        Pressure is not the same thing as complete or near complete expansion, which is where the real energy is.

        If what you’re saying were true about it bursting, the gas key would have to be nicking a pretty good “L” shape bend in the tube to trap the gas, and would likely need to somehow create a chamber in which for it to expand. The amount of expansion that occurs from the gas block, to the gas key, is trivial and serves only to deliver the gas to its destination.

        Piston systems don’t have this mythical problem because oprods don’t get very hot, and gas blocks/piston “sleeves” are generally only around an inch or two long, making them very rigid. Anything about higher tolerances is complete BS. I don’t even know of any piston kit on an AR-15 that dislodges from any part of itself at any point during operation in order to strike/misalign.

        If your problem holds any merit, the issue can be solved by simply assuring that the part of the gas tube that interacts with the gas key is more rigid and can’t droop enough to become misaligned with the gas key. There’s a million&1 ways to do this besides the ignorantly hollered “add piston like ak.” One simple route to preventing this problem of faeries, would be to make the gas tube sit in a rigid sleeve at the receiver, while the gas tube can be free to droop/whip/whatever, and have the sleeve be a shorter, rigid part permanently affixed to the upper receiver and “safely” interacting with the key in a way nearly identical to the original method.

        I believe the only company that does this, would be Innovative Arms, and not even they are gaudy enough in their marketing to slap on “gas tube won’t explode” because it would cost them all but all credibility if their spotty manufacturing capabilities haven’t already done that. Their upper receiver/gas tube serve only the purpose of adding a gas regulator at the gas key, rather than at the gas block, which is pretty much only possible on DI systems, and would be a great idea, if the bastards hadn’t patented it to throw propriety onto what would have been a great development in the aged AR-15 platform.

  • Nicholas Mew

    The other solution… Cooling Rings.

  • palmetto

    Didn’t Teludyne Tech already “fix” this problem with DG upper receiver group with a composite barrel that can take the heat and is the same weight roughly as the m4 upper?

  • Brian

    Green Mountain Defense Industries created a product through a military contract to address the heat issue and more, The link provided is the results of the test in comparison to Colt’s test. It is a complete kit to include bolt components and a thermally armored gas tube.