INTERVIEW with Kori Phillips, Program Officer for LSAT and CTSAS, Part 2: Ammunition Technical Discussion, Cont’d

Kori Phillips holds some linked 5.56mm CT ammunition side by side with a belt of 5.56mm brass-cased dummy ammunition at media day at Picatinny Arsenal on May 4, 2015. Image credit: David Vergun, public domain

Not long after SHOT Show, I got the chance to interview Mrs. Kori Phillips, former program officer for the Army’s Lightweight Small Arms Technologies (LSAT) program, and current program officer for the Cased Telescoped Small Arms Systems (CTSAS) program. We talked at length about both programs, the technology they developed, and the state of lightweight ammunition today. The interview, which spans fifty-five questions, will be broken up into three sections, each covering questions about different aspects of the program, to be published monthly once each in March, April, and May-wait, hold on,

Our Dear Leader Steve has approved a weekly timeline for the interview, instead of a monthly one. That means we’ll be finishing up by the end of March! Hooray!

This second installment covers in greater depth the ammunition technology developed in these programs. Before we begin, I would like to take a moment to thank Kori and Frank for taking the time to speak with me. They were very patient with me and did not hesitate to answer any of my questions.

Now, we’ve got a lot to get through! My questions are labeled with a bold “TFB“, while Kori’s answers are labeled with a bold “KP“:

 

TFB: What technical challenges were there in developing the plastic-cased telescoped (CT) ammunition? Was selecting the kind of polymer used a challenge? How did the technology from the caseless program affect the CT program?

KP:Probably one of the most difficult items early on was to find a polymer to use for the ammunition that could withstand the temperature range that was required, along with the extreme environment of the ballistic cycle. The team researched dozens of polymers, and ended up testing 10 or so. Of those, only one met all the requirements of the system (unfortunately, I can’t name it here, but it is a very high quality medical-grade polymer). I don’t think CT really benefitted from caseless, but certainly the caseless benefitted from CT! They use basically the same weapon, with a only a few changes to accommodate the burning of the caseless cartridge, so only one weapon needed to be developed.

 

TFB: The CT cartridge demands a firearm mechanism with a movable chamber, for single-direction feeding and extraction. This chamber dictates different design elements than standard reciprocating-action weapons that feed and extract in two different directions. How does this change affect the design of new weapons, and has it improved or degraded the new weapons’ characteristics relative to conventional firearms in any way?

KP: The decision was made to use CT because it is fully supported in the chamber, and the polymer would not be prone to failure at the back end of the case like the legacy designs. The weapon design then followed the CT ammo design, and proved to be a much simpler weapon. Feed and “extraction” all move in the same direction, so there is no issue with timing or jamming during that part of the cycle. Also, since the chamber is not attached to the barrel, it never gets hot enough to cause cook off of the ammunition, which is a safety concern for legacy design weapons. The CT weapons are also more accurate and have reduced felt recoil, according to data from user testing.

 

Kori Phillips holds linked 5.56mm LSAT ammunition (bottom) and dummy 5.56mm brass cased ammunition (top) at the Picatinny Arsenal media day, May 4, 2015. Image credit: David Vergun. Public domain

 

TFB: Other caseless and cased telescoped programs – like the Air Force’s 25mm GAU-7 that was originally intended for the F-15 – have had problems with barrel wear, specifically in the throat area. Can you tell me whether LSAT ever had those issues, and if so how they were corrected?

KP: One of the problems with some of these previous programs was that they promised other things in addition to lighter ammunition – more range, more power, etc. In the case of the 25 and 30mm telescoped ammunition, they were using a lot of propellant and very high chamber pressures, which really exacerbated issues with wear. This was one of the reasons we only promised lighter ammunition in the beginning. We wanted to work on the technology itself.

 

TFB: Later rounds appear to have no propellant in the case beyond the projectile’s cannelure. Was this done to solve the barrel wear issue, or for another reason?

KP: There was never any propellant in the case beyond the cannelure in any of the CT iterations.

 

TFB: Initial LSAT rounds appear to use loose propellant, but consolidated propellants were tried in the caseless program. Do the final LSAT/CTSAS rounds use consolidated propellants or did loose propellant give better results?

KP: The final LSAT CT ammo has compacted propellant. It is not consolidated (i.e. no binders are added to the propellant). The compacted propellant has better burn characteristics than loose propellant, and it also saves case volume, allowing overall smaller cartridge size.

 

TFB: How did the LSAT/CTSAS team solve the issue of consistently inserting the projectile into the throat of the barrel? Did this solution cause any problems? How did the team make CT rounds that have consistent bullet seating during manufacturing without a traditional case neck?

KP: The front end cap of the cartridge guides the bullet into the throat of the barrel. It does so very consistently, and the rounds have excellent accuracy and dispersion. The bullets are attached directly to the end cap during the assembly process and remain that way until the propellant has built up sufficient gas pressure to shoot the bullet.

 

TFB: LSAT has taken CT from TRL 4 or 5 to TRL 7 over the course of a decade. What was that process like, and how did your overall view of lightweight ammunition change?

KP: The important part of maturing a technology or a system is to know what the technical milestones are for each TRL. They need to be established before the development is started. Once those were established, we moved through the TRLs fairly smoothly. The more difficult part was not progressing through the TRLs, but trying to make incremental improvements along the way to the weapon design and the ammunition design.

 

TFB: There are many different lightweight ammunition concepts out there, but LSAT seemed to be centered around only two (CT and caseless). Did LSAT examine other concepts like aluminum cased or sheet metal cased rounds, and if so what did their evaluations conclude?

KP: While we were evaluating the dozens of polymer materials, we also did an evaluation of metallic cases. Aluminum was out from the start, because it is an accelerant (if it is exposed to burning propellant, it will ignite). Steel did not provide the necessary weight reductions. Based on the design of the cartridge and the weapon chamber, polymer case or caseless were the best options.

 

TFB: The different priorities of the CT configuration seem to me to be a real benefit to improving the design of the belt-fed weapon in particular. Did you find this to be the case, and did that help you reduce the weight of the weapon system?

KP: The benefit really came with reducing complexity. The cartridge overall length is shorter, which really helps reduce the size of the mechanism. The other thing is that we designed the LMG from scratch using Finite Element Analysis, which most weapons designers have not had available to them before the 2000s. So each gun designed in the ’90s or before was heavier than it needed to be because they didn’t have the benefit of computer analysis telling them exactly how heavy each part needs to be to do what it needs to do. We know by using FEA what each part needs to be made of and how heavy it needs to be, and not a gram more. The weapon is as weight efficient as any weapon is going to be; you can make it thicker or sturdier, you can add material to it for drop testing and field testing and that kind of stuff. As far as the function of the weapon goes, it’s bare-bones, as light as it can possibly be.

 

The LSAT 5.56mm machine gun. Image source: commons.wikimedia.org, credit to Tracy Robillard. Public domain.

 

TFB: You sound confident that FEA has given you a mechanism that is exactly as big as it needs to be and not any bigger.

KP: Right. We definitely proved that with the models; in the beginning we had an issue where the old gun guys didn’t believe what the model was telling them. So we went to the range to test it, and they went “wow, the model was right!”

 

TFB: The new CT belt links are, like CT cases, made of polymer. How did these belt links hold up during testing, and was there any problem selecting the right kind of polymer for the job?

KP: Through all of our testing on 5.56mm and 7.62mm, the links have been shown to be quite robust. They also were subjected to the same environmental testing that the ammunition was subjected to, with no issues. The stresses on the links are far less than on the cartridge case, so the selection of polymer for the links was much simpler. The key is that they are circumferential, not open, like current metal links. They work perfectly with cylindrical (CT) cases, but would not work with legacy ammunition due to the way the links are stripped.

 

TFB: In a previous question, you’d said it was really accurate, too. That surprised me. Could you elaborate?

KP: It is. We were very surprised to find out that the propellant burns more consistently in the compressed configuration than it does in the loose configuration. The engineers at St. Mark’s Powder, they were just as surprised as we were. They went back and they did an analysis, they did a paper on the efficiencies of compacted propellant in a cased telescoped configuration. The accuracy comes from the consistent pressure/time curves that are generated, and also the sleeve that we have inside the endcap. The ammunition is two pieces, it’s got a case and an endcap. The endcap is a heavier, more solid piece, and it has a sleeve that the bullet rides through, which is slightly undersized. It’s a resistance fit which aligns the bullet into the barrel. What we don’t know is why it’s better than brass ammo. It’s not tremendously better than brass cased ammo, but it is better. One of our theories is that when you feed a brass-cased round into a weapon, you’re putting mechanical strain on that bullet as it gets pushed into the rifling. So the bullet may be pushed into a certain orientation, sometimes slightly off-axis to the rifling. Our system may self correct for that, allowing the bullet to center more perfectly every time. We were concerned about the gap between the bullet and the rifling, everyone told us that would be a problem. It turned out to be the opposite.

 

TFB: You obviously have to have a separate chamber and a separate barrel unit. One thing that might be a negative is that on a revolver you have a gap there, where gas can escape. Do you have that problem, or have you found a solution to that?

KP: For case telescoped, the front of the cartridge actually seals the breech, and the plastic flows into the empty space. It’s sort of a balancing act to let the cartridge expand and flow, but not so much that you can’t get the case out of there. It obturates the chamber just like it would with a brass case.

 

Original caption: “Spc. Alfredo Hernandez departs through a window during an assessment of military operations in urban terrain at Fort Benning, Ga. Soldiers ran the course on the mock city twice, once with each [LSAT] weapon.” Image credit: Eric Kowal, RDECOM. Public domain.

TFB: Sort of an off-the-wall question. It occurs to me that you have this squat little cartridge case with an endcap and a certain set of dimensions. Have you guys ever tried combining that with a sabot?

KP: I can say that we have not, although they did try that in ACR. For me personally, I steer clear of sabots in small caliber rounds because they have a tendency to out-weigh the projectile, which is problematic. I don’t see any real reason not to, frankly.

One of the things that makes CT so attractive to other people in the small arms world is that it’s so easily configurable to other projectiles, so yeah, if you decided to go back to flechettes or whatever, you could do something like that. This would be a much better way to package them.

 

TFB: In 2015, Textron was showing off their 6.5mm CT carbine. It seems like there are a lot of hurdles in designing a rifle with a moving chamber like that, can you elaborate more on that?

KP: We started with a bunch of different concepts for the carbine’s chamber mechanism, like rotating, translating, revolving, and eventually we settled on a rising chamber design. It turned out to be the simplest of all of them. This was our second effort at a carbine, actually. The first one, which you’ve seen, was a 5.56mm CT with a rising chamber, too. The problem with that one was, if you wanted to take the magazine out of your gun and unload your weapon, all the sudden we couldn’t do that. The way the mechanism was set up, you couldn’t remove the magazine until the gun was empty, things like that. That was around the time that program (LSAT) was wrapping up, so we took that carbine and put it on the shelf, and in this new contract that got awarded two years ago. We pulled it off the shelf, looked at some different mechanisms, and ended up back at a rising chamber, but with a different layout. So now, operationally there’s no more issues with taking the magazine out, it works pretty normally. There are still some complications. From a personal standpoint, I fought long and hard to make it a belt-fed carbine, the links weigh practically nothing, and it helps simplify things, but the users were dead set against that.

 

TFB: That’s interesting, because I’ve talked with some other folks in the field about this subject, and they agreed that what they really should do is just issue everyone belt feds, for CT specifically. I guess that resistance comes from legacy belt-fed systems, which are frankly a giant pain in the butt. It seems like the CT MG wouldn’t be as much of a problem, is that right?

KP: No, it’s not. It’s always a problem when you’re introducing something new, it’s hard to get rid of the baggage from the previous systems. So maybe when someone comes along who’s maybe not as tied to that baggage, they will say “you know, maybe we could do a belt-fed rifle, there’s no reason that we had to have magazines.”

 

TFB: It doesn’t seem like it would be that hard to design a system where you just had a belt in a pouch that you just straight inserted into the gun, like a magazine.

KP: We’ve actually talked about it. We built a little prototype where you just shoved this little device into the belt feeder, you didn’t have to open it or anything. Once it went “click”, then you were ready to go, just like a magazine, but it was inserted on the right side, instead of at the bottom. The resistance to this idea of using belt feds seems to be based around the idea that you can change a magazine in 1 second, and it takes me 20 seconds to change a belt on a legacy belt fed. Of course, we can give them a 200 round belt, so…

But even if we end up adopting a belt-fed rifle, the work we’re doing on the magazine-fed carbine is still useful. I think it helps us understand what the benefits of designing things a certain way are, and you can always apply that information back into the next iteration.

 

TFB: The compacted propellant, is that basically just SMP-842 that has been compressed, or something?

KP: Yes, it’s a variant of ball powder. They had to tweak the blend to get the right pressure curve for CT, so it’s not an off-the-shelf propellant, but it is similar. St. Mark’s will not tell us what the difference is, that’s their proprietary info. The powder is literally pressed into the case, without any kind of binder or glue. There’s nothing sticking the balls together. The compression takes out the air gap, so you end up with like 1.1 grams/cc density, so a bit over 100% loading density.

 

The third installment of this interview will be published in May next weekend! Stay tuned!





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 is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • Ευστάθιος Παλαιολόγος

    The third installment of this interview will be published in May. Stay tuned!

    If your going weekly then you should correct the above also…. 🙂
    flanker7

    • See above comment about ‘raging moron’. 🙂

      • Ευστάθιος Παλαιολόγος

        Just saw that I used “your” instead of “you’re”…
        Not the least flattering about myself either…
        Oh well. I can blaim my 40 years if age now

  • Giolli Joker

    Good news indeed!
    Great info in this 2nd part.
    Good to know the I had guessed right the gas seal part.:-)

    • N

      It was quite logical, i dont get how Nathaniel tought any diffrent, both the large area for the pressure to push the casehead forward and in other versions direct visible gas seals.

      • Because I’m a raging moron, as everyone knows!

        • N

          Naw~ poor Nathaniel no your not *patpat*

          • Hahahah! Self-criticism is my best attribute. 🙂

        • iksnilol

          Yeah, I’m still baffled by your fanboyism for a hypothetical M14 chambered in 6.8 SPC…. as a standard issue carbine none the less.

          Like, how can you even defend such a ridicilous thought?

        • Twilight sparkle

          Even if that were true (which it’s not) you still write most of my favorite articles on this site.

  • TechnoTriticale

    It took like 600 years to move from loose powder and ball, with separate ignition, to the self-contained metallic cartridge.

    Copper, then brass, and sometimes aluminum or steel cases have now dominated for some 150 years, despite numerous experiments to eliminate them, going back to Volcanic, if not earlier.

    Caseless doesn’t seem to be going anywhere, but replacing metal does.

    So shifting to polymer, or polymer cased-telescoped is rather a big deal, historically, and I suspect there’s a lot of institutional inertia, if not robust reactionary resistance to it. Communication outside of the R&D community is therefore an important part of getting the widest possible awareness of the merits, debate, and perhaps public support – hence, I suspect, this interview.

    Polymer CT might just be a military transition, unless the per round cost ends up lower than reloading, in which case (no pun intended), it might broadly appeal to civil users as well, who are usually less concerned about things like having to carry 200 rounds all day in unpleasant climates.

    • Johannes von’ Strauch

      Less heat flux, less barrel heating, less chamber heating, less pressure, less powder use due to less conductivity of polymer. Strong points for civilian use in my book.
      Besides that far better (more reliable and space efficient) mechanism. With less moving mass that cause less felt recoil…

  • Major Tom

    This info is proving that LSAT/CTSAS might very well just be one of the few actually innovative weapons platforms of the last 60 years. Or at least innovative weapons platforms that happens to be more or less production ready.

    • randomswede

      It seems they’ve approached the project from as blank a slate as possible. Without “reinventing the wheel” and without assuming the wheel in use is the best starting point for something new.

      • roguetechie

        Yup, it’s pretty obvious that they’ve carefully examined the designs from past CT weapons and various designs for various items related to the folded ammunition concept.

        The reason I believe that they looked at design materials from the folded ammunition concept relates to early talk coming out of the LSAT program that a CT LSAT carbine upper could be developed for the M16/M4 which would essentially give you nearly 4 extra inches of barrel from a conventional cased upper with the same OAL…

        Some of the early presentation materials and documents strongly hinted that said uppers had already been constructed and were in testing.

        I’d very much love to know one day whether these really were built, and if so why the approach was abandoned.

    • Let’s just hope it doesn’t go the way of many of the other actually innovative weapons platforms: designed, perfected, then shelved.

      • Ballistic

        Wrong, the Innovative Weapon Platforms where innovative, and had potential. Theyr problem was theyr where not perfected.

        • SP mclaughlin

          Whayt?

          • Ballistic

            What im saying is that most Innovative Platforms from the past, beside theyr high potential where just not perfected enough.

          • roguetechie

            Again… Not even close to true

          • Twilight sparkle

            A lot of people frequent this site from countries where English is not the main language… give people some slack, that person was perfectly easy to understand.

        • roguetechie

          That’s completely untrue in quite a large number of examples I know about personally…

      • roguetechie

        No freaking joke…

        However CT small arms ammunition has actually met it’s 50 year cooling off/waiting period (ya know like buying a handgun in blue states) between it’s first appearance in prototypes and the first successful product using the new concept / technology…

        A great example of the 50 year waiting period is the hill SMG first appearance of the top mounted magazine with rounds t to the barrel, and the successful launch of the FN P90 almost exactly 5 decades later!!!

        • Now they just need to bring out a 9MM PS90 with a Hill SMG magazine and I’d be a very happy camper.

          • roguetechie

            Hah I want one in .30 carbine / 7.92 vbr long and or 7mm Penna / 7 Penna long.

            The 7mm Penna ones wouldn’t be at all difficult since 5.7 FN is it’s parent case and there’s something like a several millimeter lip in the P90 magazine which could be deleted since it was added in because at the last minute they went with a different bullet that was a few mm shorter than the original loading and they didn’t want to redesign the whole magazine!!

          • 7mm Penna would be really cool; as I understand it it’s just a straight wall 5.7×28 case no?

            It could probably be done with just a barrel change, but projectiles would have to be kept to 40gr or bellow, as the PS90 experience “popped mags” from full power, heavier loads. And this would require using a very light material for the projectile.

            Something like a 7mm Zinc Spoon tip round could be interesting.

            But really, I’m quite happy with the performance of the 5.7×28 (especially the more boutique loads.) I just want a 9mm as a cheap, fun plinker and suppressor host.

            FN is probably worried about cannibalizing sales of the 5.7×28 platform, but man, they would be printing money if they offered a PS90 in 9mm.

          • roguetechie

            Yeah, the P90’s operating system is deceptively complex from what I understand so anyone short of FN itself or someone who has the cash to essentially buy a license to produce them which includes full technical data package and a bunch of development documentation etc would have a very hard time building a 7mm Penna P90.

            You are correct though in thinking that one possible approach is keeping things similar enough to avoid getting outside the stock pressure curves etc.

            If I were to take this approach I’d be looking really hard at a cbj-ms style sabot and a 5mm projectile that takes cues from 4.6 interdynamics AB rimfire, 5.56 FABRL, and 7.92×40 cetme Voss.

            Like you said though they should just make one in 9mm para… However I’m in love with weird, obscure, boundary pushing, and otherwise interesting cartridge and gun designs.

          • Giolli Joker

            7Penna (7x23mm) is not a straightened 5.7×28, AFAIK it was developed from the ground up.
            Very thick casing as well, designed to deal with overpressures and to deal with blowback operation also at high pressures.
            I shot a prototype of the first series of pistols and it was quite a sweet gun.
            The load designed for military use (and “air marshal” use) had extremely light, high speed aluminum bullets. Actually the pistols designed specifically for these loads were smooth barrels (LE/military only) or with a very shallow straight rifling (civilian use) to get the highest velocity for short range use.
            The fastest load “on the market” was a 45grs bullet at 500+m/s, those “military” loads were supposedly above 600m/s.
            I can’t link to sources because most of what I remember comes from a personal talk to Eng. Leonardo Penna and the sources online (even in Italian) are pretty much all gone.

  • John Daniels

    This is fascinating information, and I’m looking forward to continuation of the series.

    • randomswede

      Off topic but your avatar suggests that you too are a fan of the JRE; always interesting to see where interests converge.

      • I like watching Rogan because for the most part he keeps an open mind. I don’t watch him religiously or anything, but I’ve seen a decent amount of his stuff. He seems like a decent guy for sure.

  • ARCNA442

    Thank you for accelerating the release schedule.

    There is some very interesting information in this interview.

  • Uniform223

    Wow this is so exciting. Can’t wait for part three.

  • LGonDISQUS

    Aluminum was out from the start, because it is an accelerant (if it is exposed to burning propellant, it will ignite

    Powdered Alu will ignite at a wicked temp, but solid Alu… man, it has to be over 900°c or something, no?

    • Johannes von’ Strauch

      … just let it to the experts, aluminium FABRL cases did burn decades ago, even under 39000psi compared to usual 55 to 58kpsi.

      Polymer is better at literally everything. Less conductivity, which results in less heat flux, less barrel heating, less chamber heating, less pressure, less powder use.
      And at a lighter weight too…

      In therms of price, electro smelting aluminium is known to be rather expensive.
      And i also wouldnt be to interested to fill ground water of foreign countrys with aluminium nitride etc (or whatever the toxic stuff was) with hundret-thousands of cases spend in combat in the middle of nowwhere. Neighter… my own country or home.

    • noob

      get it to burn up completely and you have a caseless metal case?

      • ostiariusalpha

        Except burning aluminum leaves aluminum oxides behind, such as corundum, one of the hardest naturally occurring substances next to diamond. I don’t think you want corundum condensate in your firearm, because good luck trying to brush that out of the bore.

        • noob

          ah good point. that’s pretty much sapphire dust?

          • ostiariusalpha

            Yeah.

  • Don Ward

    Good news everyone! Sanity has prevailed and this series has been moved up to a weekly. Thanks TFB.

  • uncle fester

    Thank you for the series. I am finally starting to understand why this might be a big deal someday.

  • .45

    I’m going to have to watch some videos or look at some diagrams of the internals and reread this, because I don’t really understand what is going on. I barely know anything about this at all, and it’s hard to extrapolate from almost nothing.

    • .45

      I feel like I could worded that better. I don’t mean to say the material is too confusing or that the article has no substance to it, I mean to say I lack the background info to really visualize what they are talking about. Not having read much about the project, I feel like a Civil War era fellow who has only ever seen muzzle loaders overhearing a conversation about the new Henry lever action. I just don’t know enough to follow. (Everything goes in one direction? I have to see this…)

      • Jay

        Search youtube for this video:

        Textron Systems – Lightweight Small Arms Technologies (LSAT) [720p]

        It explains the function of the weapon really nice.

        • gunsandrockets

          That was a big help. I finally understand how the chamber-barrel gap is sealed by the LSAT case. It’s obvious once you see it. I’m embarrassed by my earlier confusion.

          And it occurs to me that the LSAT method of sealing that barrel gap would be directly applicable to existing revolvers. Imagine a .44 revolver with a custom barrel bored out to only .357 inches. The custom ammunition would fire a .357 bullet contained in an LSAT style endcap, and the endcap is fitted to an ordinary .44 cartridge case in place of a normal .429 bullet.

      • In retrospect, the biggest problem I have with this interview is that it’s really addressing an “intermediate” audience. For those who aren’t already familiar with LSAT, it is very confusing.

        The reason for this is that I’ve been following LSAT since their powerpoint presentations first started going up on DTIC. I’m no expert on the program, but I am a huge windowlicking fanboy of it. So I tried to cover a lot of ground, but even so I didn’t get basic enough for those who aren’t familiar.

        Something for me to keep in mind for the next time I do an interview. I need a set of five or so really introductory questions, that would help a lot.

        • Giolli Joker

          I guess that if you just link your previous work on it, and maybe Anthony G. Williams page on it as well, anybody can get enough background to understand everything that is said in the interview.
          There is nothing extremely technical that requires specific knowledge other than an overall idea of the project.
          You could also do a fourth instalment with: What we know on LSAT, covering a bit of premises and including an analysis on the data collection performed during the interview.
          Anyway, it’s great content!
          Thanks!

          • That’s a good suggestion, I hadn’t really thought of that. Yeah, I might take you up on it.

          • roguetechie

            +1 on this suggestion!

            Speaking as a fellow window licking LSAT fan boy, a single what we know post like this would be a valuable resource.

        • Aono

          That sounds like one of them good problems.

    • This will help!

      • noob

        interesting shape on the cartridge ram. it’s not circular but sort of a crescent shape. Is that for FDM prescribed lightness?

        Also I am curious about the manual of arms – if you wanted to clear the weapon after firing you’d open the feed tray and remove the belt, but then you’d have a round in the chamber. how do you get the round out of the chamber without another round to push it out?

  • Hrachya H

    So it seals the gap between the chamber and barrel much like it was in Nagant revolvers … pretty interesting!

    • randomswede

      But now with plastics! Better living through chemistry and so on.

      • roguetechie

        And almost exactly like the crye six 12

    • noob

      could somebody make a revolver handgun that has sealing CT bullets and a smaller bore size than chamber size using this principle? it might make an interesting silenced pistol that retains the fired cases.

      bonus if it uses rifle projectiles like the old soviet captive piston guns used to – which would give the impression that the target was struck by a rifle from many yards away instead of a pistol from close range.

      • gunsandrockets

        The LSAT method of sealing a barrel gap might be easily applicable to existing revolvers. Imagine a .44 revolver with a custom barrel bored out to only .357 inches. The custom ammunition would fire a .357 bullet contained in an LSAT style endcap, and the endcap is fitted to an ordinary .44 cartridge case in place of a normal .429 bullet.

  • Jay

    Thank you very much for recording this interview and speeding up the release.
    This is really great info.

  • This was a really fascinating installment.

    The possibility of a belt fed carbine was especially interesting, as well as the institutional resistance to the idea.

    Kind of reminds me of this scene from The Fountainhead:

    “Your Greeks took marble and they made copies of their wooden structures out of it, because others had done it that way. Then your masters of the Renaissance came along and made copies in plaster of copies in marble of copies in wood. Now here we are, making copies in steel and concrete of copies in plaster of copies in marble of copies in wood. Why?”

    One question, and this could play a deciding role in mag vs belt, is if the moving chamber required of PCT is compatible with a balanced recoil action?

    Because with balanced recoil like in the Ultimax or AK 107 + belt fed + lightweight weapon, you could have a really “universal” weapon, that would work well in both the carbine role as well as in the role of the SAW.

    The increase in firepower per squad with 3 out of 4 men armed with belt feds would also open up the 4th man for use of more specialized / exotic weapons such as a smart grenade launcher, PIKE launcher, mini drone operator, 6.5 PCT DMR man…

    • Fate

      Dude… the chamber moves downwards, no need for a “balanced recoil system”, it shoots as smooth and is way more reliable from the beginning…

      6.5 is going nowhere it has extrem downsides and is overcome by other more modern configurations.

      • So the chamber moving downward provides the same lack of recoil as the Ultimax 100?

        • No, the reciprocating part of the operating group has a longer stroke like the Ultimax.

          I don’t remember where, but IIRC the Ultimax was at some point explicitly referenced in an LSAT presentation.

          • roguetechie

            Yup, and with half the feeding and chambering cycle happening on the recoil cycle and half on the return to battery cycle you’re already starting out with a more balanced kinetic energy situation.

            Throw in the pivoting chamber which could let you do some interesting stuff with buffering on both the recoil and return stroke…

            Yeah, the whole thing is really damn interesting

    • Once upon a time, my online handle was “roarkeating”. Let that sink in…

    • some other joe

      Belts vs box magazines
      For a general purpose weapon, I go with the form factor of the box mag. Faster reloads is of minimal importance. More important is enclosing the system when I’m dragging the beast through whatever. If the belt comes in a fully enclosed drum, like the MG42 or, better yet, the USCM M56 smartgun ;), then maybe carrying 200 rounds in my rifle becomes feasible.
      How heavy is total loaded system (optics, lasers, lights, ammo, etc) with FEA and polymer advantages vs an M4 or its counterparts.
      But at that point, what’s the benefit of linking the rounds vs having them loose with a spring and follower? Can the same polymer technologies involved in the links produce a similarly lightened spring or other magazine components?
      If we’re going to 200 rounds in the gun, now how many reloads do Joe have to carry? Does he suddenly have no ammo on his vest or belt? Only single pouch with another 200 round box? Carrying only a large SAW pouch for ammo could reduce the volume of crap Joe carries, even if doesn’t do as much for weight. What does a tactical reload look like? Do I worry about it if I’m pretty sure I still have over 160 rounds left?

      • The big problem with magazines and PCT ammo is that the magazines greatly negate the weight savings of the new ammo in two serious ways.

        To begin, a PMAG weighs 4.9oz unloaded, 17.2oz loaded. A standard combat loadout is 7 mags (1 in gun + 6 on vest.) So that’s 7.53lbs, of which 2.14lbs is magazines. So 28.5% of the weight is made up in magazines.

        Now if you reduce the ammo weight by 40%, but the mag weight remains the same (likely, as the mags have to remain very durable) then you’re not really getting a 40% weight savings. By my math, assuming magazine weight remains the same, 7 loaded PCT mags would weight 5.37lbs, which is only saving 29% weight – only 2.16lbs. Hardly worth spending billions of dollars on!

        Now 29% would be a great weight savings if you were carrying more ammo, but that gets to the other important issue with magazines – it’s very hard to carry lots of them. A standard chest rig can only carry 6, so to carry more either belt mounted pouches would be required, or the soldier would have to go full bandolier.

        By going belt fed, both issues are solved. There is no wasted weight from magazines, and there is no wasted space from magazines. That makes it much easier for the soldier to carry much more ammo in the field, and translate the weight savings of the PCT ammo into a significant increase in combat effectiveness.

        With a 200rd pouch inserted into the gun, and one spare 200rd pouch on the chest rig, the soldier would have doubled their combat loadout from 210rds to 400, with only a 1lb increase in weight compared to a 7 mag 5.56 loadout.

    • roguetechie

      There is a very big difference between ak-107 system and the ultimax system.

      That said, this is VERY compatible with any of several soft recoil schemes.

  • notkak18

    what if the sabots were filled with compressed propellant, having high pressure chamber going into the low pressure chamber of the barrel, similar to how 40mm grenades work

    • That’s some mad science you’ve got going on in there.

    • jcitizen

      I think you could do the same thing with dual burn powder, so the pressure spike is more like a flat burn.

  • Tassiebush

    I have no experience with belt feed (guessing Nerf doesn’t count) but since this is the realm of experimental ideas it seems like the whole belt feed Vs mag feed reload issue could possibly be resolved in the favour of belts with a stiff link section or bars of stiff links like a hotchkiss. If they were disintegrating they’d probably be able to be inserted vertically. This could mean having a “beltwell” to enable a belt to be shoved in quicker with more control rather than the more fiddly current set up.

    • roguetechie

      LOL…

      I gotta give you points for creativity Tassie but oh god no that’s a horrific idea LOL… Just teasing of course.

      Being serious though

      This is actually a problem that’s already been solved multiple times and doesn’t require anything Hotchkiss like, nor would it be fiddly in the slightest.

      Gene Stoner when he worked at Ares on their ACR entry designed a very simple drum and belt setup for his CT ammunition design the Ares AIWS was chambered in. It was inserted and removed basically the same as an AR15 drum and just as quickly. However said drum had the advantage of being VERY small for something that held 100 rounds of belted ammunition.

      Then we have the Jiri Cermak designed URZ universal weapons system out of Czechoslovakia. Again we see a very compact drum for something that fired belted 7.62×51 ammunition, even though he added a couple very unique, unorthodox, and ultimately extremely handy features to his drum design. Like the Stoner AIWS drum inserting, removing, and getting a fresh round into the chamber from a fresh drum was only marginally slower than a standard detachable box magazine.

      Finally we have the solutions several of the companies developed for the guns they entered into the SAW competition. All of which were faster than 20 seconds… Except for the “winning design” aka the FN M249!

      Truth be told, this is the army doubling down on the stupid decision made in the SAW competition.

      AkA … No army it is in no way required that swapping a belt and belt container take 20 seconds you just picked a design that sucked as the winner to that competition too!!

      • Tassiebush

        Hehe well I’m still going to patent the “stiffy feeding belt”
        Those were some interesting and good ideas for the belt feed systems. As always thank you for improving my understanding!

        • roguetechie

          If I was on my other machine I could have posted a dozen pictures showing you the relevant items, however I did put enough information in the post for you to be able to Google the various things.

          If you have a copy of the black rifle volume 2 the Ares AIWS pictures are in there for you to see.

          • Tassiebush

            I shall enjoy looking it up 🙂

  • Tassiebush

    It’s very interesting to read that tests indicate that this system and round improves accuracy. Given the barrel and chamber are separate.

    • gunsandrockets

      Well, it all depends on how you look at it, right? The LSAT has a chamber which moves, as opposed to a conventional firearm which has a breech which moves.

      In both cases you have a barrel with a severable part. In contrast to a muzzle loading firearm where the barrel is one piece.

      • Tassiebush

        Well yeah true a poorly aligned bolt face or inconsistent lock up and a poorly aligned chamber occur frequently enough with current technology so I guess it might not be any more problem prone to make a chamber that aligns perfectly. It’s familiar turf with revolvers I guess and this only needs one chamber.

  • jay

    You can’t post videos if you are not registered. That’s why i didn’t post it. If you add a video or image in a post and you are not registered, it’s never published.

  • Aono

    Regarding the “unexpected accuracy” portion of the interview, there are factors besides superior concentricity and St. Marks’ consistent compacted powder charges that could be at play. A handloader tweaks seating depth, concentricity, and neck tension. Handloaders also pick cartridge cases that have long necks to more fully support the projectile bearing surface, and more easily manage those three factors.

    For maintaining better concentricity to the bore, or “run-out,” the CT rounds are certainly likely to be more robust throughout the entire autoloading process, with a fully compacted powder encapsulated projectile, and no exposed soft brass shoulders or bullet tips to ram into barrel extensions. The CT case’s sleeve has a very long “neck” indeed, and would fully support the bullet’s full bearing surface while it accelerates into the lands.

    I doubt that the ogive actually has much of a “jump” to make at all when measuring from the muzzle end of the CT sleeve to the lands, which is sure to matter more than the unfired distance from where the bullet sits loaded behind the sleeve. The undersized sleeve would be acting like a small length of smoothbore until the lands begin, not like the gap of freebore we normally think of when a projectile makes the “jump.” FX airgun “smooth twist” barrels are an example of a very accurate barrel that makes the transition from smoothbore to “twisting.”

    I would also imagine that the polymer molding process lends itself simply to very good dimensional consistency. It would be really interesting to know how consistent in weight and volume the polymer CT cases are when compared to e.g. the best Lapua brass cases. High dimensional consistency would make for a consistently strong interference fit in the sleeve, consistent powder charge weight, etc. It’s also possible that the polymer material itself has a more consistent friction coefficient than brass, whose “grippiness” can vary widely depending on whether it’s brand new, once-fired, fresh out of an ultrasonic, etc.

    I look forward to seeing where this eventually heads for civilians, because it seems very promising on all fronts. The “hulls” could become the least expensive component of the projectile. A bio-
    or photo-degradable polymer would make an interesting option for many. Hell, it could even unseat rimfire due to case vs hull cost alone. What could a caseless 22LR replacement look like?

    Great job again Nathaniel.

    • Giolli Joker

      Great points.
      I’m too interested in seeing a development for civilian shooters; I can picture for example an X-frame revolver shooting a 6.5CT round for “long” range pistol hunting/target shooting.
      However I do not think we would see effects on all cartridges.
      For example short cases and bullets (pistol rounds) or very small rounds .22LR, would not be dimensionally suited to be replaced by CT.
      CT rounds would rather work well with bottleneck cartridges, shaving off some OAL possibly at the expense of a a diameter increase.
      Without going into CT technology, yes, we could have better, cheaper polymers employed in manufacturing casings, but I doubt it would be anything really revolutionary.

    • Tassiebush

      This was one very interesting attempt at a caseless .22lr replacement. Daisy airguns made a rifle that used hot piston driven air through a venturi to ignite the rounds. https://youtu.be/IHNg6laaiWo

      • roguetechie

        Tassie,

        The V/L system is one of the most likely ways to make working case less ammunition we have with the limitations of current materials science and technology IMHO…

        It always makes me happy to see someone else bring it up as a likely approach.

      • jcitizen

        I had to get rid of mine, because it was too inaccurate.

        • Tassiebush

          I’d wondered how it performed. I’d thought that the piston mass moving might impact accuracy too. Gosh you have or have had some really interesting gear!

          • jcitizen

            I’ve been interested in firearms and armament design since I was a kid – can’t always afford such a hobby though! :p

            I always wondered if Daisy shouldn’t have built the attaching part of the base of the bullet to resemble a small round rocket chamber, instead of the v notch post they used. That way if there was any unburned propellant, it would at least burn in a balanced geometric way, and possibly not disturb the exit from the muzzle so much. The piston was pretty smooth, and better than most pellet guns. I was amazed how clean everything was – there seemed to be no residue ever. I didn’t have my own cartridge fired rifle yet, so I was pretty disappointed. I was so looking forward to hunting with the thing.

          • Tassiebush

            It’s almost like it wasn’t constricted enough to generate the heat and just pushed them out! The rocket idea sounds cool!

          • jcitizen

            I wondered about that back then, but I didn’t have calipers to compare bullet to bore diameter. It may have just needed a simple skirt like other pellets to assure a better seal. It did seem to have constant velocity though.

          • Tassiebush

            Oh yeah loose fit would be bad. I was thinking more of the venturi but bore fit makes as much or more sense.

          • Tassiebush

            It seems like a surprise that no-one has done the same approach for a muzzle loader.

          • jcitizen

            Now that they make powder “pucks”, it may be that the manufacturers feel that would be redundant. At least with those, all you have to do is drop the puck in the bore before seating the bullet. I really don’t know why they don’t go all the way and make a reproduction paper covered ‘cartridges’ at least for reinactors, so they wouldn’t have to make their own.

      • georgesteele

        I still have mine, but ammunition is very hard to find and expensive when you do find it. It never was particularly accurate, most probably for the reason explained below. In addition, occasionally there was a misfire – probably insufficient heat in the air ignition. Not insurmountable, you would think, but history now.

        • Tassiebush

          It really was a fascinating concept! I wonder if they ever thought about how to extend the technology into a repeater because it seems that making that step would have posed quite a lot of technical difficulties using the compressed air ignition approach.

  • Madcap_Magician

    This is a very cool interview series.

  • Dig Dug

    I hope that if this is adopted that they’ll take the opportunity to make some of the weight-neutral but performance-enhancing improvements to the form factor of .224 bullets that Nathaniel has talked about in other posts on caliber configuration.

    I’d also be very interested to see how this could be applied to PDWs. The CT 5.56 is already shorter than the overall length of a round of 5.7×28 (1.556 in v. 1.594 in), and is almost as short as 4.6×30 (1.516 in). That’s getting to where it could comfortably fit in a pistol grip (I’ve read that the 5.7mm is tough for people with smaller hands). I don’t think that the full-powered 5.56 would be the way to go for a PDW with the blast and violent cycling from a short barrel and gas system, but imagine something along the lines of a CT version of the 5.56×30 MARS that was optimized for a short barrel. Especially if instead of a 55 grain 5.56 bullet they used something more efficient like a 5.45mm bullet of similar weight with a better BC. With construction similar to the new EPRs, that could be a compact but very effective weapon.

    • Nameless

      Dont worry, something similar is under work, and yes in (an enhanced) EPR, not by Textron tough. I know what you mean by 5.45 ,its good compared to shapes in use right now, but actually extremly poor compared to what is coming.

  • gusto

    Isn’t it time for lasers anyway?

  • jonp

    I’m still waiting for a reason we need this?

  • georgesteele

    I found her comment – that the reason for excluding Aluminum was that Aluminum was an “accelerant” (poor description – basically an ablatively sacrificial enclosure) – to be odd; that seems to be a positive, rather than a negative. If a thin aluminum case is used to contain the powder and bullet, is moved out of an encapsulating link into the chamber on loading, and obturates the combustion gases until the aluminum is consumed (presumably leaving small amounts of aluminum oxide, etc. behind), then the subsequent round (since these things are cylinders, rather than tapered or shouldered cartridges) could simply push that residue out of the way into the lead/throat clearance space upon loading, and the residue expelled behind the bullet upon firing by the combustion gas. Essentially, a self-cleaning chamber. This is somewhat akin to using the incoming cartridge like a piston during the exhaust cycle of a motor. Perhaps magazine feed could use a compatible encapsulator, or be eliminated in favor of belt-feed. I wouldn’t think the lack of a primer would be unsolvable, using some combination of piezo/capacitive/battery/solar/wind power/nuclear/whatever ignition mechanism, or coating the base of the Aluminum case with primer compound. Anyway, I found it curious.

  • georgesteele

    When clicking on the link for the 3rd installment of this series, I get a 127.0.0.1 can’t be found error message. Where is the page that we can just see all of this series listed in order?