Textron’s LSAT Program Unveils 7.62mm Plastic-Cased Machine Gun Mockup

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The Joint Service Small Arms Program (JSSAP), which includes the program formerly called Lightweight Small Arms Technologies (LSAT) has unveiled a new scaled-up 7.62mm machine gun that fires a larger variant of that program’s cylindrical plastic-cased 7.62mm ammunition. Military.com’s KitUp! reports:

TAMPA, Fla. — Textron Systems showed off its newest effort to develop an ultra-light 7.62mm machine gun at the 2015 Special Operations Forces Industry Conference.

The new MG is being designed to weigh 14.5 pounds – more than eight pounds lighter than the lightest version of the M240.

The effort is part of the Case-Telescoped Weapons and Ammunition program which has produced a matured 5.56mm lightweight machine gun similar to the M249 squad automatic weapon, according to Textron officials.

The newer 7.62mm version is under contract with Joint Service Small Arms Program Office to develop the operating system to handle the larger caliber, according to Ben Cole, mechanical engineer for AAI Corp., owned by Textron. JSSAP is based in the U.S. Army’s Armament Research, Development and Engineering Center at Picatinny Arsenal, N.J.

Formerly known as the Army’s Lightweight Small Arms Technologies, or LSAT, the program is designed to lower ammunition weight by 40 percent as well as producing significantly lighter infantry weapons.

The result would be a 14.5-pound 7.62mm case-telescoped machine gun, compared to the Army’s M240B machine gun which weighs 27 pounds. The new, lightweight version — the M240L — weighs about 22 pounds.

The overall effort has already produced a 5.56mm CT weapon that weighs 9.4 pounds, compared to the M249 SAW, weighing in at approximately 17 pounds.

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Military testers have fired about 85,000 5.56mm CT rounds through 10 test guns, said Cole, adding that the weapon has gone as far as it can go until the Army decides if it wants to make it a program of record.

A firing prototype of the 7.62mm CT weapon is expected to be ready by the fall of 2016, Cole said.

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US military programs are notorious for taking a long time to complete, and small arms programs in this country tend also to be underfunded. It’s no surprise then, that the 7.62mm plastic-cased machine gun firing prototype is expected no earlier than late 2016.

Initially, the LSAT program’s plastic-cased ammunition began as a telescoped type, with the projectile buried within the propellant. Theoretically, this reduces the size of the ammunition, and allows a neat, cylindrical form factor that  However, as this mid-1990s report from Inspector General’s Office notes, telescoped ammunition is not without its drawbacks:

Cased telescoped cartridge designs are larger in diameter than conventional cartridges, thus providing a larger volume for propellant. Therefore, in the programs reviewed, typical cased telescoped ammunition contained two to three times the weight of propellant charge compared to the baseline conventional ammunition for a given caliber. Table 1-1 shows the conventional and cased telescoped ammunition data obtained from the Services.

Table 1-1 indicates that the higher muzzle velocity achieved by cased telescoped ammunition as compared to conventional ammunition is a function of higher propellant charge weight. A comparison of the muzzle velocity between conventional ammunition and cased telescoped ammunition with respect to projectile weight and propellant charge weight indicates that cased telescoped ammunition is less ballistically efficient than conventional ammunition. For a given caliber, a cased telescoped cartridge weighs more and occupies more volume than a conventional cartridge of the same caliber. As a result of the higher propellant loads in cased telescoped ammunition, a significantly higher temperature and heat input is imparted to the gun barrel and barrel life is significantly reduced.

The additional bulk of ammunition mentioned in the report is evident in one of the early LSAT Spiral 1 5.56mm ammunition prototypes, shown at left in the picture below:

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This early ammunition used standard propellant, and was approximately the same diameter as a brass-cased 7.62mm NATO round, costing a significant amount of bulk versus conventional brass-cased 5.56mm ammunition. The LSAT team further improved the ammunition by using improved propellants, but eventually the telescoped ammunition concept was apparently quietly dropped, as the latest 7.62mm plastic-cased prototypes show propellant not fully encasing the projectile in the case, which remains cylindrical and externally similar to earlier ammunition:

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Some LSAT ammunition, from a 2011 shoot. Note the 7.62mm concept round, laying on the ammunition box, and that its propellant chamber does not extend past the cannelure of the bullet. Image source: kitup.military.com

 

While this alleviates issues of barrel wear, and allows a much more efficient use of the propellant (and thus much less of it), LSAT machine gun prototypes appear to still be chambered for Spiral 2 or 3 ammunition, also visible belted in the above photo.
Beyond the issues surrounding telescoped ammunition, the moving chamber mechanism also invites problems of flame-cutting, similar to those experienced by revolvers. LSAT machine guns have to deal with this issue somehow, as they are (unlike revolvers) fully enclosed, and fully automatic. It’s my suspicion, therefore, that while propellant and material technologies pioneered in the LSAT/JSSAP program will be incorporated into future ammunition, the LSAT ammunition configuration itself and the mechanism used by the LSAT machine guns will likely both be dead ends.



Nathaniel F

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


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  • hikerguy

    You may be right. I do think LSAT bears worth watching for more development, however.
    Depends on wether Textron and /or the military is still really interested or not. But it looks like brass is here for a while to stay for the foreseeable future.

  • Giolli Joker

    I hope you’re wrong. I believe advantages overcome drawbacks.
    I believe as well that the plastic cap that closes the CT rounds offers some level of gas seal, that, if not eliminates, reduces gas cutting.

    • I don’t think so, but the diagrams of the mechanism I have are fairly old.

      • Joshua

        The polymer crimping cap used in the current design does seal the gap between chamber and barrel.

        • Am I just gonna have to take your word for that? 😉

    • Whoops, here you go:

      So far as I can tell, the plastic cap does not offer gas seal. I do not know how they are counteracting the flame-cutting problem.

      • Giolli Joker

        Fairly old video as well, that just shows a very generic layout of the mechanism.
        My reasoning is that the cap will have to withstand the pressure building inside the shell, this will push it forward and the bullet will pierce through its center. If the gap is as limited as it is on most revolvers, the internal pressure would make the cap adhere to the barrel throat face, successfully channeling gasses only behind the bullet.

        • I hope they have done something like that, but I do not know.

  • Matrix3692

    I’m always wondering this question: can the AR survive the CT/CL transition?
    maybe with a swap of an upper receiver, can the AR family be converted to fire CT/CL ammo?

    and by the way, does the “Have A Tip?” button on the right of the page still work?

    • nobody

      >can the AR survive the CT/CL transition?
      That’s unlikely. The way that the CT/CL ammunition feeds requires the top of the magazine to not be inline with the barrel (as the chamber has to move separate from the barrel and cases have to be able to move in through one end of the chamber and out the other) which would be hard to accomplish while still keeping the AR15’s magwell and barrel location, using the same FCG, and without sacrificing magazine capacity. All of the ways popping into my mind on how a CT/CL AR15 could feed would involve so many modifications that the gun could only vaugly be called an AR15 with the only common parts being the lower receiver minus anything related to the guns function other than the FCG, the handguards, and the sights. It would have about as much in common with current AR15s as the .50 BMG uppers that you can get.

      • MR

        Yeah, depends on what is meant by “survive”. There are still 1903s and Garands around, and some M14s in military service, so they’ll likely be around as a commercially viable product. If you mean, can they be converted to fire caseless or poly cased ammo, I’m sure they could, but it likely wouldn’t be the most efficient design available, and likely not suitable for military use. Something for a niche commercial market, like the crossbow upper receivers, and the previously mentioned 50 BMG uppers. At some point there’ll be a weapon that offers significant improvements as a general issue weapon, over the M4/M16 family. It just isn’t here yet.

      • Joshua

        One design goal is a upper receiver that uses the current lower of the M4. There was some talk of having the case be ejected out of the mag well similar to the P90.

        It may not happen, but that was a design idea of the carbine variant. Of not they will develop a full rifle.

    • I am not optimistic that the LSAT configuration will have much of a future, but I think it’s probable that next-generation plastic-cased ammunition will be designed for reciprocating actions, and it’s conceivable that AR-15 lower receivers, or possibly even their uppers as well, could be redesigned for the new ammunition.

      “Have a Tip” just sends you to the tip email: tips@thefirearmblog.com

      • Matrix3692

        so if i saw something that I thought I should recommend to you guys, should i just email there?

    • Not really, which is why the LSAT program is *also* designing a carbine that fires the same rounds as the LMG. It’s one or two iterations behind the LMG spiral, because it got started later.

      If the LSAT technologies are developed to TRL9 (the LMG is at about TRL7, the carbine and GPMG are probably around TRL5 right now), expect to see the standard rifle, LMG, and GPMGs to be adopted pretty much together — probably near the same time, but with the LMG and rifle/carbine set at the same time, maybe a slight delay on the GPMG.

      I do *not* expect to see conversions to the CT or CL rounds from existing conventional cased ammunition, because the cycle of operations are so different, due to the natures of the ammunition. It would be like expecting Maynard tape repeaters with ball and powder magazines in the butt to be converted to smallbore smokeless powder high velocity military rifles.

      • LilWolfy

        TLR7 was reached in 2012 from everything I’m seeing. Prototypes were out-performing the SAW in leaps and bounds before the gun even matured.

        • Yup. As I understand it, they still have some cost targets in ammunition manufacturing to hit…

  • Riot

    So just lighter than the conventional PKM with a barrel that is a bit over half the length.
    Dear god its a wunderwaffe!

    • Joshua

      Don’t forget the weight savings of the ammunition.

      • Riot

        Except its bigger and heavier than normal stuff. And will need advanced propellants etc – As Nathaniel said above these improvements could be used for conventional gear.

        • Joshua

          No it’s not, and Nathaniel has no first hand experience with this stuff so he honestly has no idea. Unless he was at Maneuver Battle Lab, which I doubt.

          He even says it is no longer telescoped when clearly it is. Having the bullet inside the case is telescoped.

          Polymer is both lighter and cheaper than brass.

          While I like Nathaniel this article is full of conjecture from someone with no real first hand use.

          • Riot

            At what point did I say polymer was heavier…….
            If we get polymer casing working flawlessly it could replace metal in a conventional cartridge. And clearly the differences in weapon design in order to use this new type of ammunition is negating the advantage over a conventional cartridge layout. Since this modern, designed with lightweight in mind and no doubt costly weapon is as heavy as a half century old design geared towards economy.

          • Joshua

            You said CTA is heavier than normal stuff.

            CTA is generally 40% lighter than similar brass cased ammunition, mainly due to the polymer used.

          • ostiariusalpha

            Polymer does not work at all well in a conventional bottle-necked case design, they need that metal to expand and create a gas seal for proper operation. A polymer case needs the special chamber they’re using in the JSSAP, which also happens to work best with case-telescoped ammo.

          • I agree that “drop in” ammo seems unlikely. I suspect the next step will be polymer cased conventional-looking ammunition with thicker case walls and new chamber dimensions.

          • No first hand experience, that’s correct, but I’ve been following the program closely from its inception.

            If you want to argue semantics, I’ll leave you to it. The bullet is no longer buried in the propellant like previous rounds. There is a reason for this, which is related to the inherent downsides of telescoped ammunition (low propellant use efficiency, flame cutting due to gases escaping in front of the projectile, etc).

            While I’d love to fire me some CTA through an LSAT machine gun, I don’t see how my not having fired a 20 round belt at a demo invalidates the official sources at my disposal, and considering that less than 100k rounds of CTA ammunition have been fired total, ever, the chances of anyone, much less a humble blogger, getting to do a torture test that could produce real data seems slim.

            I don’t see how what I’ve written is conjecture when it comes from official reports and photographs of the actual ammunition. Given this, your comments come off as spurious and bitter, honestly.

        • ostiariusalpha

          The current 5.56 CT ammo is 40% lighter than regular 5.56 NATO. This 7.62 CT will also be lighter than the 7.62 NATO it is designed to replace. Where did you pick up the impression that it would be heavier? It was only the very early prototypes of the 5.56 CT that had the cartoonish large case diameter, and even they were still lighter than the standard brass cased stuff. The propellants are optimized for this CT ammo, it wouldn’t really benefit brass cased ammo in any direct way.

          • Riot

            “early ammunition used standard propellant” and the newer lighter stuff uses more advanced propellants.
            You can change the propellant in conventional cartridges as well.

          • Joshua

            Yep and it will still be heavier than CTA.

          • ostiariusalpha

            I don’t think you fully understand what makes this propellant an advancement. It isn’t that it is somehow “MOAR AWESOME” than other propellants with better energy output, it has to do with it’s capacity to resist heat. The reason that the earlier CT ammo was so fat had to do with needing to protect the standard propellant from a hot chamber, which is less of a concern for standard brass cases that can act as a heat soak. With the polymer, they had to use thicker walls to keep heat from transferring to the chamber and the from that chamber to the next round, all to avoid a cook-off; this is much less of a concern with the new propellant. There might be some marginal benefits to having cook-off resistant propellant in standard brass cased ammo, but weight wouldn’t be one of them.

          • I think, actually, their initial prototypes suffered from propellant packing issues.

        • Jay

          Wrong on all accounts

        • Erm… I didn’t say that plastic-cased ammo was heavier than normal ammunition.

    • LilWolfy

      It’s about half the weight of the PKM, with balanced recoil, and ammo that is 40% lighter than existing M855 linked.

      Win, win, win, with serious overmatch on several levels, especially when you load it with the M855A1 projectile.

  • Luis Cabrera

    You’ll need to have passed the LSAT to afford a semi-auto version (if one ever happens)

  • Lance

    Dont trust this plastic telescoping cases. Too many moving parts and items too much to go wrong in dirty and gritty combat.

    • LilWolfy

      LSAT MTBF is about twice as high as the PIP M249 according to 11B’s who spent 2 years in the test program for this at Benning and Ft. Richardson. It’s way more reliable than the SAW, and 9.4lbs versus 17lbs. It’s also easier to shoot with than an M4 when looking at recoil and hit probability because of the recoil system.

      The SAW was always a problem for us in the Infantry Squad and Platoon in terms of malfunctions and maintenance, from operator level to higher where armorers pass the breakages off to Brigade-tiered maintenance.

      This program is actually addressing one of the main weak points in US small arms, and from everything I’m hearing from actual Joes in the testing, they love it, can’t wait to see the SAW kicked to the curb finally.

  • That’s certainly true, but that doesn’t imply there are no technical challenges facing the LSAT MG. Let’s not repeat McNamara’s mistake with the AR-15 and act like it’s a totally battle-ready off-the-shelf option. IIRC even the old LSAT PM characterized the technology at TRL 7.

  • Should have expected all the jerking over 6.5mm caliber. Everyone thinks it’s on the horizon for LSAT, which is funny because I’ve never seen a 6.5mm LSAT round, ever, despite 7.62mm ammunition existing

    As far as I know, the only reason that idea has been mentioned by the LSAT team was in the program’s “Epilogue”.

    • The 6.5mm CT cartridge can be seen mentioned on the display behind Kori Phillips at Picatinny’s recent media day.

  • John

    The solution seems to be make plastic instead of brass bullet cases.

  • kev

    I have high hopes for this technology, while its still a bit off and the finished products will probably look nothing like the prototypes the technology and methods will and are finding their way into next generation ammunition with the marines already testing polymer cased conventional 50bmg and 300winmag rounds with metal bases and primers. However i think it will have to be a somewhat private endeavor as the U.S. Government is more keen on spending on planes and other contraptions all in all long live the LSAT and whatever it will be.

  • Hoookay, that is news. Interesting, though, I hadn’t noticed it. Gotta be wrong sometimes. I do get to say that I still haven’t seen a 6.5mm CTA round, though, ;P

    I want to see a whole lot more data on the feasibility of a 6.5mm round to fill both roles than is currently publicly available, because holy cow could that turn into a bean counter fiasco.

    • LilWolfy

      6.5mm would overmatch 7.62x54R and 7.62 NATO easily. This .30 bore horse crap needs to be phased out. You can have 6.5mm CT that weighs less than existing 5.56 linked, with less wind drift and flatter trajectory than any 7.62 NATO load, more retained energy on target, with less recoil and lower pressures.

      Since we are no longer beholden to brass cases and traditional chambers, the compatibility argument goes out the window really fast, as belt-fed weapons don’t use mags.

      • That isn’t the whole picture, and it’s not so overwhelmingly favorable to the 6.5mm as many would have you believe. I’ve written about this many times before; there are other considerations such as recoil, projectile type and volume, the benefits of CTA ammunition in smaller calibers, etc.

        Compatibility isn’t a concern for future weapons, but configuration is a huge concern, and I think it will always be true that you can do more with two calibers than you can with one. I don’t think the ballistic profiles of 5.56mm or 7.62mm are optimum, but that does not mean the two-caliber system should be thrown away for another “do-it-all” military procurement fiasco.

        • LilWolfy

          You won’t see me advocating for a single-caliber system. It’s just not realistic nor is it appropriate, not that small arms are huge factors in warfare anyway.

          A 130gr 6.5mm load in a new Multi-role LMG makes sense to replace linked 5.56 and 7.62, but you have the potential for overperformance issues for the common soldier, who does not need 1200m + capability with his individual service rifle or carbine.

          LSAT does provide the option of just using different projectile weights with the same bore diameter, but I would also be concerned about the cartridge dimensions for soldier’s load, where 5.56 and 5.45 are pretty hard to beat right now.

          What will happen though, if this gets fully fielded, is that Joe is going to feel how light it is, and then see the onboard ammunition capacity, and start doing some field math real quick.

  • Esh325

    I can understand making a 7.62mm just for the heck of it, but honestly 7.62 caliber should NOT be their choice if they choose to adopt it. A 6mm-7mm would be better and save weight.

    • ostiariusalpha

      They have a lot 7.62 bullets, I’m guessing. I’m with you about using a higher BC bullet though, leaves room for more propellant or smaller cases also.

    • Seburo

      They are already working on a 6.5x47mm version. At the same time as the cased version.

    • Just as they have been doing the developmental work with M855 projos in the 5.56, they are using 7.62mm projos in the GOMG version, so they can compare apples to apples. Otherwise, people would be screaming how they only achieved their goals by “cheating”, since they are comparing different calibers with totally different performances.

      Once they show the substantial advantages in the new system, then the time comes to explore the best projo designs and ballistics.

  • LCON

    If they pull his off It will be the lightest 7.62mm GPMG in the World.