Army wants lightweight cartridge cases

The Army is looking for vendors who can supply alternative cartridge case technologies to reduce the weight of 5.56mm M855A1, 7.62mm M80A1 and .50cal M33 cartridges by 10%. The cartridge cases must be able to be used by the Lake City Army Ammunition Plant.

FBO Solicitation number W52P1J12R0166

The Government is seeking sources for alternative cartridge case technologies that provide a 10% weight reduction while maintaining all performance requirements when fully assembled as 5.56mm M855A1 (190g), 7.62mm M80A1 (392g) and .50cal M33 (1782g) cartridges. Suppliers must provide a description of their alternative cartridge case material, manufacturing process, Load, Assemble and Pack process (LAP) and submit tested capability with documented results. Future capabilities with timelines and level of effort required to meet the weight reduction should also be included. Respondents are to submit a unit price for the M855A1, M80 and M33 light weight cartridges assembled with their alternative cartridge cases and a projected ROM based on an annual rate of 1million per year, per cartridge. The assumed projectile costs are as follows: M855A1 ($0.15), M80A1 ($0.20) and M33 ($0.25).

Respondents need to show the capability of their cartridge cases to be manufactured in quantities totaling approximately 45 million per year.

PCP polymer cased ammunition. Photo © Gregory Markle

Other than polymer cases does anyone know of any other lightweight cartridge case technology (caseless is by definition not a cartridge case technology).

[ Many thanks to Travis for emailing us the link. ]

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.


  • Nathan

    What about ceramics? If they can make paper out of stones now, why not cartridge cases? I don’t imagine it being that much lighter than brass, but a certain ceramic alloy might make the required 10%. Just an idea. I have no data on this whatsoever.

    • Brian P.

      That’s some interesting thinking. I never heard that paper could be made from ceramics before. Sounds a bit odd, to me.

      • godanov

        You can do all kinds of stuff with ceramics. There is much technology out there. A normal ceramic case would be too heavy, but a case made of alumino-silicate ceramic fiber and resin of some sort, a la fiberglass or carbon composite would be feasible.

    • MrDakka

      Ceramics are usually a good alternative to metals, however in this application, they are not ideal.

      The metal cartridge helps to alleviate heat buildup since they are heat conductors. Thus the heat generated from firing the bullet is removed with the ejection of the cartridge. Ceramics, typically are heat insulators and thus heat could build up in the chamber to potentially dangerous levels. IIRC this was a significant problem with the G11 and its caseless ammunition.

      In addition, most ceramics are rather brittle (they might have high tensile strengths but have low toughness; they may crack when firing the bullet). Thus when you try to eject the cartridge, it ends up as a spray of broken pieces.

      There are certain engineering ceramic composites (transformation toughened zirconia, exotic cermets and MMC’s) that could potentially address these issues, but are too expensive to fabricate on a mass scale.

      • Trev

        Ceramics are very brittle! Glad you pointed that out.

        This is also the reason that ceramic plate armor, while able to take a bullet, is only good for a very limited number of hits.

        Ceramics, much like glass, shatter.

        They do have the benefit of being light in weight for their abilities.

      • Jeff

        I think you’re a little backwards the fact that metal is a good conducter is what allows heat to be conducted from the combustion, through the cartridge, and into the chamber wall. If the casing is an insulator of any sort, that heat is both absorbed and held in the insulator but otherwise travels through the path of least resistance, out with rest of the combustant. A conductor is just any path of easier travel. Given the thermo dynamics if the goal is remove heat you want something with a high coefficient of heat absorbtion with an insulating property that keeps the heat trapped in the ejected portion. Metal isn’t that.

  • Brian P.

    So, would steel cases not make the cut in weight reduction? What about aluminum alloys? Blazer uses aluminum cases for a lot of their ammo, right? I see no reason aluminum couldn’t be used. It’s much lighter and cheaper than brass.

  • Pat

    How about aluminum? CCI Blazer style……
    ..or would there be pressure/temperature issues?

    • Nathaniel

      Aluminum cases were trialed by various militaries from the late forties to the late ’70s. They typically require an internal combustible liner (because aluminum burns) which reduce case capacity for a given external geometry, and are happiest at moderate pressures.

  • glok blok

    this was tried before by several countries about 25 years ago. they used plastic cases with some level of success. of course, they wont function in HK weapons because of the chamber flutes. aluminum has been used for years, but may not be tough enough to withstand the rigors of belt feeding.
    the only way to accomplish this will be with a newly designed metal case of some sort. the ammo makers are going to need some very talented metallurgists to pull this off.

  • Jeff

    10%? Why bother? 10% is neither here nor there surely.

    • Zappy

      10% off every single round adds up fast.

    • Nick Pacific

      It’s half a pound off of a soldier’s load, which is nice, but think of this larger scale. 10% of all your small arms ammo shipping. It will still take up the same space in a transport, but the weight loss means significant fuel savings in an organization like the military.

      • junyo


        10% doesn’t seem like much, until you need to figure out the logistics of moving a hundred tons of the stuff.

      • Jeff

        Or in the least, its a half pound of extra ammo on your back.

  • Medic760

    I used to know an Officer from the National Guard. He was also an engineer for Lockheed Martin. One project he was working on about 8 years ago was a Boron doped brass that reduced case weight by approximately 40%. His comment was that he and his colleagues were having trouble stabilizing the matrix. He also said that if they could stabilize it, the compound should promise of being able to be loaded to higher pressure than standard 855 ball. As far as cost, I was told that the process would have zero impact on the net cost of the individual round, or possibly, reduce net cost. If he were to be successful it would be a big win for end users. Any time you can decrease weight without affecting combat readiness, you improve on combat effectiveness.

    • matt

      “the compound should promise of being able to be loaded to higher pressure than standard 855 ball”

      The brass typically isnt the limiting factor, you can always make the cases thicker and use a faster powder to make up for the reduced capacity, the limiting factor is the hoop stress the barrel can take.

  • Leonard

    Maybe some kind of carbon-based material could be used in the future. E.g. this:

    “German scientists create world’s lightest material” – The Local, 18 Jul 2012

    • Trev

      The only issue I see is that carbon products are extremely expensive at the moment.

      If you have ever priced carbon fiber guitars, car parts, helmets, hand guards ect. it’s not cheap.

      • Bryan S.

        Trev, that depends on the technology used to create teh carbon fiber parts.

        Carbon forged pieces are coming along to reduce the time of laying CF, which is the big issue when it comes to cost. Enough so that companies like Ferrari and Lamborghini are using them in production cars to save costs and reduce weight.

  • Zappy

    If it was up to me Id look at a type of Silicone resin. once the round it chambered, the chamber its self is what keeps the brass from deforming. but I’m no scientist, or gun smith, so what do I know.

    • David/Sharpie

      That would be okay for mag fed guns, but I don’t think it would work too well for belt fed guns.

  • JAFO

    The administration caught hell when they started scrapping old brass in an effort to hamper the ammo market for civilians- this new process is not about saving weight so much as it is about hampering the civilian arms market. Mark my words.

    • Leonard

      I am sorry but this argument seems rather paranoid to me…

      • David/Sharpie

        I agree..

        Plus its the Army doing this, not the administration

    • W

      what about aluminum casings? I wonder what the weight difference would be…

  • Overthetop

    One problem not mentioned very often with polymer cases is storage in a magazine for longer periods of time. Case deformity is a real problem when polymer cases are under pressure in a magazine. If my memory serves me right, aluminum cases had the same problem.

  • Jay.Mac

    I’d much rather hear that the military was going to adopt a new intermediate (as in mid-way between 5.56mm and 7.62mm) round, such as the 6.5GPC – – to improve terminal ballistics, reduce the number of weapon platforms needed and ease logistics. Once troops are equipped with the best, most effective cartridge available come back and we’ll discuss 10% weight saving proposals.

    • Esh325

      It’s not going to happen. I think you’ll see the 5.56×45 and 7.62×51 for another 20 or 30 years.

      • Tyler Marcoz

        Particularly given we already have weapons that use it and it works perfectly fine. The M4 had some issues given it was firing rounds designed for a longer barrel, but the newer stuff does just fine, and it has the benefit of, you know… already being there.

        All for new stuff, but the logistical nightmare of rechambering all your rifles, not to mention the cost, makes it a no-go. Plus, it’s just not necessary.

  • Trev

    Tin foil much?

  • Pete Sheppard

    MrDakka in the first response, mentioned that ceramics could cause excessive heat buildup in a weapon due to its insulating properties. I’d have thought the opposite, that the ceramic would insulate the weapon from the heat of the powder combustion and carry it away from the weapon upon ejection, thus keeping the weapon cooler. Am I remiss in my thinking?

    I think we’re reached the apix of firearms cartridge. Until revolutionary breakthroughs are made (caseless, electromotive, liquid or something unimagined currently), brass alloy is about the best there is.

    • bbmg

      It might spare the chamber from heat transfer, but you have the rest of the barrel exposed to the heat of the propellant gas.

    • 6677

      Most of the heat is absorbed through the barrel rather than the chamber, a large amount of combustion is still occuring in the barrel.

  • Trev

    The main consideration in my opinion is energy. Energy, in the form of heat needs to bled from the chamber to prevent “cook offs.”

    Polymers are really resistant to thermal exchanges.

    Metals have the best (generalization) thermal conductivity properties for the situation.

    So, cheaper metals….

    • K!P

      but more heat in the case isnt bad, it spits it out after firing. heat transfer goes both ways.

    • Zermoid

      I would think the case being an insulator would be a good thing, that much less heat transferred to the chamber’s steel would be a good thing, no?

      Wonder how they will deal with chamber heat? Most plastics will melt or at least soften at high temps, be interesting to see what happens to a round left in a chamber that just fired a couple of belts of ammo rapid fire.

    • Jeff

      They are resistant to thermal exchange, but that means they actually insulate the chamber from the heat. They slow the exchange that normally allows the chamber to get hotter.

  • gunslinger

    i’m all for material advancements.

    25 years ago someone tried it… that may be the case, but advances in material technology could make this a real possibility.

    i guess just have a good spec to aim for, and throw it at the “nerds”. 10% weight reduction means an “extra” round you can carry for every 10 you normally carry.

    but if i could get polymer cases for 1/2 the cost or less? awesome.

    speaking of which. how much of the total round cost does the case comprise of? i mean, if it’s 50% of the cost. and the polymer is 50% less, with the bullet, powder, primer and manufacturing time/process the same…that would lead to about an overall reduction in cost of 25%.

    • RocketScientist

      In general, the case (when made in brass) is one of the most expensive components in a round of loaded ammunition. When you consider the cost of the material (copper alloys are usually one of the pricier non-precious metals) and the amount of manufacturing put into that part (it had to be machined and formed to very specific dimensional requirements, QC’ed, etc) it makes sense. The bullet itself is usually made predominantly out of cheaper materials (lead/steel core) with a small amount of expensive copper or similar (cladding/jacket). Also, with a projectile, youre mainly concerned with 2 metrics: total weight and OD. Of course length and boattail taper and ogive profile and all that are of concern but primarily, if your bullet weight what it should and its diameter is what it should be, then you’re good to go. This makes manufacturing less costly.

  • Esh325

    Lighter weight cartridge cases are definitely needed with the amount of weight a soldier has to carry today. While polymer cartridge cases have been unsuccessful in the past, I don’t think that means they are totally unfeasable. I think we’ll see polymer cartridge cases being used heavily in the near future.

  • ctfrazer

    how about a 30% weight reduction

  • snmp

    steel case are ligther than the brass. In plus that’s cheaper

  • bbmg

    Can the semi-combustible cartridges used for modern tank rounds be scaled down?

    • 6677

      An aluminium casing would fit the bill for semi combustable and was precisely why the idea of an aluminium case was dropped, dangerous to the operator ejecting a case that is physically on fire (or at lease smouldering)

    • noob

      in a brand new weapon system, yes. in this case (pun not intended) the design brief is to keep the mfg process and weapons unmodified and just drop in a new cartridge case that is magically lighter than brass

  • FormerSFMedic

    The answer is already right under the Army’s noses. This company could easily do this for 5.56 and 7.62.

    I think some readers here are missing the point. How much difference does 10% make? Well, on an aircraft, or for a soldiers load out, or for logistics, it can make a big difference. However, it’s not all about saving 10% weight it’s about being able to carry 10% more!

    • Marine Doc

      Major problem is that the military believes today’s military members are more of a pack mule then they are a mobile fighting force. Having to field a sixty pound pack and more is ridiculous. I can’t ever remember carrying any where near that amount when I served with the Marines in Vietnam. With all of the resupply options available today, they should be carrying LESS, not more useless equipment, then they could carry more ammo.

      • Phil White


        I read Marcus Luttrells book and they carried over 125 pounds in their packs on that fateful mission in the Afghan mountains.One of the first things they did when they came under heavy fire was dump gear.

      • 6677

        Bravo two zero, probably greatest SAS failure ever, one of the first things they did: dumped all their kit. Good choice or bad choice, who knows. 3 good troops lost their lives on that mission, 2 from hypothermia which had they had their kit they probably wouldn’t have. Had they not dumped their kit though all 8 of them may have been KIA, who knows.

        I think weight reduction of a soldiers kit, no matter how much, is certainly a good thing.

        And before anyone moans about L85’s being heavy (which they are of course), the bravo two zero op they used the colt canada AR15’s

      • David/Sharpie

        6677: All 8 did not die.

        3 Died, 4 were captured and later released, 1 escaped.

  • Lance

    I still see high temperature problems with polymer cases. Don’t know LSAT will solve this problem and offer whole new tech on small arms. But still I dont see the problem with brass worked well for the last 200 years.

    • BillCa

      Sure, brass has worked well for about 170 years. But let’s consider the changing world environment too. Brass is made of zinc and copper. The price of copper was recently at a high and IIRC China was buying up scads of it for future uses, perhaps even as currency.

      Why seek an alternate alloy?
      * Lighter weight as indicated. Lighten the troop load or increase ammo capacity within the same weight range.
      * Lower unit cost per round.
      * Corrosion resistance in long term storage (e.g. 5-10 years or more)
      * Non-reusable case – either by enemy forces or US civilians (for some materials)

      Lower cost and weight is a huge plus. Lower cost in the future means the .Mil can still purchase ammo on a more restricted budget. Lower weight means savings all around on transportation (until you get to the grunt who gets to carry more ammo).

      Re: Barrel heat – the burning of the gases probably creates the most heat, but remember too that bullet friction also creates significant heat, especially in rock ‘n roll mode. I’m also curious as to what happens with polymer cases that are left in the chamber after extended F/A fire. Seems to me that any polymer could melt just enough to leave goo in the chamber. Once that cools it’d be a bear to remove.

  • Geo

    I got my hands on some of the plastic .223 a few months ago. They were nice and cheap, but quality was low. If you pinch the plastic shell and pulled on the bullet they come apart. Tested them in a Galil and an AK. The Galil handed them ok, but my friend’s AK has some issues. The plastic walls of the shell would rupture as they were extracted and jam.

    • Esh325

      That really doesn’t prove anything.

      • Geo

        Proves that’s they won’t work in a poorly manufactured American AK clone. Sorry, I just calls’um as I see’um.

    • Chase

      In order to prevent them from coming apart, refrain from squeezing the case and pulling on the bullet.

    • Phil White


      Who made the ammo? I’d really like to know.

      • Geo

        I don’t know who made it. A friend gave them to me and gave me the following story: The Military showed interest in buying plastic ammo. Some company made a shit load of them. The contract to buy them floundered and the company went bankrupt. Some congressman probably stepped in and thought it was a really bad idea. Maybe they changed their minds and are interested again. It’s possible I got a first generation that they have improved on since. Hard say’in not know’in.

        • Phil White


          Gotcha thanks for letting me know.

      • Geo

        I found one kicking around in the bottom of an ammo box. It say PCA 05 on the brass rim.

  • Tony

    Plastic casings is not a new concept. As long as it is still cheaper to use copper or steel, plastic casings will not be widely spread.

    • Esh325

      It’s not a new concept, but it’s a concept that’s never been successfully applied before to small arms yet, and the new offerings look like they might change that. That’s what the buzz is all about. It might take a few years for polymer cases to catch on. Cheap is not the only things that matters.

  • Sian

    We’ve been looking at these lately, polymer cases are about ready for prime time. They’re a bit closer to ready for the larger calibers (.50BNG, .338 Lapua) and actually are producing better accuracy than brass now. Economies of scale and they could easily be cheaper than brass.

  • Brandon

    I want 5.56mm ammo for 15 cents a round!

    • Andrew

      I think it’s saying they will pay 15c per CASE not per loaded round.

      But yeah, I’d enjoy 15c / rd too. ;^)

    • A

      Projectile cost is $.15, not cartridge cost.

  • SteveD

    Light weight ammo case is fairly easy to make and durable. The technology exists right now without going to exotic. Once the production is set up, these could be far less costly to manufacture.
    Powdered Carbon will do the trick.
    Very light weight.
    Easy to make. I know a couple companies that have the ability technology and would be able to do it right here in the US.
    Carbon is able to withstand enormous amounts of heat without deforming.
    Could cut the weight of the cartridge in half.
    Undetectable by metal scanners (could be a problem)
    Also while at it, what about the bullet?
    You could also make a carbon bullet, it would be far lighter, and travel faster.
    It is the difference between getting hit with a Bowling ball or a bullet.

    • Laingatang

      The last thing they need to do is make bullets even lighter.

      • Charles222

        They’re not talking about the bullet. They’re talking about the case. 😉

      • John Doe

        Or we can just throw out the Hague Convention and bring back hollow points.

      • Laingatang

        I know we are talking about the case, it was in reply to the comment I replied too funnily enough.

    • bbmg

      A lighter bullet would travel faster, but slow down quicker, and I’m guessing the Army is looking to use their rifles beyond a few feet range.

      Maybe some sort of saboted “cookie cutter” round:

  • The U.S. Army doesn’t need to be trading in commodities.

  • A considerable amount of work has been done in recent years in making cases out of sheet stainless steel, as reported in various presentations to NDIA conferences (including the last one, in Seattle in May, which I attended). The steel is punched into shape, then given a light alloy plug in the base to hold the primer. Weight saving over brass is 40% for the case, or around 20% for the complete loaded round. Some 100,000 of these cases were made last year for testing.

    Polymer cases (with metal bases) initially got a bad rep, but they have been improving considerably with newer materials. Two different companies are currently making them (MAC LLC and PCP) are they seem to be doing well in military tests. Weight savings are around 25-30% for complete rounds.

    Aluminium alloy cases have been around for years and work OK in low-pressure pistol rounds or in cannon calibres, but no-one has ever been able to get them to work satisfactorily in high-pressure small arms. They split too easily, and the material can suffer from burn-through. There are some hopes that new alloys will help, but don’t hold your breath. Potential weight savings for a loaded cartridge could be 30%.

    I am surprised that the required weight reduction is only 10%. You could come close to achieving that with coated mild steel, which the Russians and Chinese have been using as standard for decades.

    • Denny

      “I am surprised that the required weight reduction is only 10%. You could come close to achieving that with coated mild steel, which the Russians and Chinese have been using as standard for decades.”

      Precisely; and that puzzles me too. One feasible explanation is that BRASS has provided for better business. I am affraid this is NOT about technical supperiority at all. Call it a conspiracy, if you wish.

      No, seriously, I can see suitable drawn quality aluminum (with lesser diferential in size of neck and base and post-form heat treatment) as realistic way forward. Stainless steel is heavy and far more expensive.

    • Denny

      And also – an this is crutial: aluminum makes better heat sink. Do not remember seeing this part in discussions. I was always impressed seeing that ICC .40cal Blazer coming from gun smooth like ironed slacks.

    • Denny, the stainless steel cases I mentioned aren’t drawn from a thick disc like brass cases, they are made from thin sheet. They use far less metal than brass cases, which is why they are so light (40% lighter than brass cases, 20% lighter for the overall round). They are also cheaper than brass.

      • Denny

        Allright, thanks for feedback. You are certainly closer to source than many of us. Good day! D.

  • Tinkerer

    Reading the comments, there seems to be the running idea that spent brass acts like a sort of “heat sink” that absorbs heat from the hot chamber, and takes that absorbed heat with it once ejected. Well, if I remember my thermodynamics, heat is supposed to flow from a high temperature zone to a lower temperature zone, not the other way around. Now, inside a barrel, that means that heat flows from the hot combustion gases -which is the highest temperature zone in the system- and towards the barrel. And in the case of the chamber portion of the barrel, that means that heat flows from the hot gases, THROUGH THE BRASS CASE, and into the chamber, so the brass would be in fact HOTTER than the chamber, and it would simply NOT ACT as a heat sink. So, the fact that polymer cases are made of heat-insulating materials -instead of the heat-transmitting brass-, would actually hinder the transfer of heat from the high temperature gases towards the lower temperature chamber,meaning that the chamber would heat up less with polymer cases than with brass cases.

    On the other hand, we can’t ignore the transmitted heat from the rest of the barrel towards the chamber, so the chamber will eventually heat up anyway. And in that case, with a hot chamber, ANY metal case would transfer heat from the hot chamber into the propellant -with increased cook-off risks-, while the heat-isolating polymer case would in fact isolate the propellant from the heat in the chamber. That is, a heat-isolating polymer case would in fact PREVENT COOK-OFFS in a closed-bolt firearm, while a heat-transmitting metal case would facilitate cook-offs.

    • Your reasoning is correct, but you’ve omitted something: when a fired brass case is ejected, it is very hot. A polymer case is not, because it is too good an insulator to absorb much heat. The brass case is therefore removing heat from the chamber, which the polymer case cannot. This is not a huge factor – only a small percentage of the heat generated by firing is removed in this way – but it does exist.

      • Tinkerer

        I would think that the brass case is hot because it is heated directly by the combustion gases. Like I said: the hottest zone in the system will be the combustion gases themselves, and the temperature differential will dump the gases’ heat to the case, and then to the chamber. That is the reason why spent brass is so hot once ejected.

      • Correct – but the key point is this: firing a cartridge in a gun generates a certain amount of heat, and all that heat needs to go somewhere. If heat is not taken out of the gun via the ejected brass case, then the temperature of the propellant gas will be slightly higher, and this will heat up the gun rather more – not the chamber directly, since a polymer case insulates that, but the barrel. Of course, barrel heat will work back into the chamber.

        The net result of this is that if you have two identical machine guns side by side, both firing through a long belt of ammo but one brass-cased and one polymer-cased, the gun with the polymer ammo could be expected to be hotter at the end of the firing, because the brass cases will have removed heat from the other gun.

        Whether that matters or not would need to be tested – I rather doubt that it would be a significant factor.

      • Tinkerer

        Tony, your hypothesis of “if heat is not taken out of the gun via the ejected brass case, then the temperature of the propellant gas will be slightly higher,” is thermodynamycally unsound. The heat from the barrel cannot raise the temperature of the hot propellant gases, because those gases are at a much higher temperature, and unless you have a heat pump you cannot migrate heat from a medium of lower temperature to that of higher temperature -and the heat pump requires an external energy source and take advantage of the rapid expansion of a vaporizing liquid in order to work-. The gases CANNOT have tehir temperature risen “slightly higher” or at all. Simply put, the heat will ALWAYS move from the gas towards the case and the barrel. What DO happens is that gses -because they’re gases and have very low mass- have a very low specific heat even if they have very high temperature -think of how you can stick your hand inside a hot oven and keep it for a few seconds without ill effect, but can’t do the same with boiling water, even if the temperature in the oven is higher than that of the boiling water: the hot gasses have comparatively less heat -that is, energy- than the denser water. Same happnes with the gases and the barrel: the gases are very hot, but with comparatively little heat, so the barrel heats up just a little with each pasing shot. It takes several shots to get the barrel on a high enough temperature, because the dense steel barrel can hold a LOT of heat. But still, once it absorbs a lot of heat from the gases, the temperature of that large amount of heat will STILL be lower than the temperature of the combustion gases. And considering that the brass case have a very low mass -compared to the barrel and chamber-, and how the case is heated directly by the combustion gases, with each fired shot the case will absorb heat and reach a higher temperature than the chamber, and so, there will be NO heat trasnfered FROM the chamebr and INTO the case -beacause of the temperature differential-, but it will be on the contrary.

      • You have missed or misunderstood my point, and are busily attacking a “straw man”. I never suggested that heat from the barrel could heat up the propellant gases – that is obviously nonsense since it is the propellant gases (plus the friction of the bullet passing down the barrel) which generate the heat.

        What I said is that heat from the hot propellant gases is absorbed by the brass cartridge case which is then extracted from the gun, taking heat out of the gun. That transfer of heat slightly cools the propellant gas (it has to – law of conservation of energy) which means that the propellant gas cannot heat up the gun quite as much as it otherwise would. A polymer case absorbs very little heat from the propellant gas, therefore the gas is not cooled down by this, therefore more heat from the gas is transferred into the barrel, so the gun gets slightly hotter than it would with brass cases.

      • Jeff

        The amount of heat energy that needs to be removed and the coeficient of heat absorbtion of the material would be important to consider. Just because it doesn’t get physically hot doesn’t mean the plastic isn’t absorbing the heat. The space shuttle’s tiles were insulators who’s primary purpose was to absorbe heat. The heat generated from the combustion within the cartridge only has two paths it can go: into the casing or out of the barrel as gas. By being an insulator it prevent heat tranfer from the cartridge to the weapon, this should actually serve to reduce the oscillation of heat extremes that can contribute to material failure in a weapon, potentially increasing the service life of the weapon, reducing costs, and allow for the cheaper manufacturing of future weapons.

        Another aspect to consider is that while the outside of the polymer casing remains rigid, the amorphous nature of plastic in high temperatures potentially provides the advantage of changing phases. If the inner most layer of plastic absorbs enough heat to start to melt that is more energy removed from the system than just the saturation point of the material.

      • Those are interesting points, Jeff. Clearly, they will only be resolved by experiments to reveal just how much heat polymer cases can remove from the gun compared with brass cases.

  • Sal

    WTF happened to LSAT?

    Why don’t they just take the telescopic cased polymer material and construct a conventional case?

    • A conventional case made entirely from polymer would not work in a machine gun or automatic rifle because the material is not strong enough to withstand the violent extraction forces – the extractor claw would rip through the rim, leaving the case in the chamber. That is why all polymer versions of conventional cartridges retain a metal base of some sort.

  • John Kensington


    this topic has pretty much covered metal alloys, polymers and ceramics but what about combustible cartridge cases? The technology has advanced quiet a bit for large calibre tank and mortar ammunition but has – to my knowledge – never been applied to small and medium calibres.

    Though i naturally could think of some disadvantages off the top of my hat, i’d be intruiged to hear what thoughts come to minds here first.

    Cheers, JK

    • In practice, there’s little difference between combustible case and caseless cartridges. LSAT had another go at caseless ones alongside the polymer-cased version, using HK G11 technology bought from Dynamit Nobel. They have made little progress, however, discovering (as has every attempt to produce caseless small-arms ammo) that the technical problems are too great.

      The problems include the need to use very expensive (and I understand often toxic) high-temperature propellant which can be formed into a cartridge; the vulnerability of the unprotected propellant to environmental conditions; the risk of the propellant breaking up, leaving chunks of propellant (and primers) stuck in the mechanism; the lack of protection from chamber heat. These were all described at length by Jim Schatz in his NDIA presentation on caseless ammo:

      • bbmg

        The Benelli AUPO round mentioned in the presentation is interesting, the “semi-caseless” round certainly seems to offer a good compromise on the face of it.

        Then again:

        “One of the major detriments is heat, as the traditional cartridge case acts as a heat sink and removes a significant amount of thermal energy form the gun when ejected. Benelli hoped to address that disadvantage with the 9mm AUPO ammunition, by providing a long and thin brass cylinder to absorb heat and then leave the gun with the bullet. However, adding that extra brass also pretty much negated the theoretical advantage of lightweight caseless ammo. In addition, maintaining a way to extract and eject live rounds left the gun no simpler than any other blowback subgun – more complex than many of them, in fact.”

      • John Kensington

        Greetings Tony,

        I think putting the technical risk of combustible cases (CCC) en par with caseless ammunition does not do it justice. With CCC you can still use regular ball powder and just replace the brass cartridge with nitrocellulose based cases that may be coated additionally. No fancy Dynamit Nobel G11-type newly developed powder is required.

        Cheers, JK

      • That’s a fair point, John, but it’s interesting and possibly significant that no-one seems to have looked at combustible cases for small-arms ammo in living memory (well, my memory anyway!). In fact, the only successful use of a rigid combustible case (as opposed to bagged and modular artillery charges) I am aware of is in AFV guns, particularly the current NATO 120mm tank gun. The smallest calibre I know of with a combustible case is the South African 76mm Rooikat armoured car gun.

        Note that this AFV gun ammo is not entirely combustible. There is a stub metal base, for the same reason as in polymer-cased versions of conventional ammo – to give something rigid and strong for the extractor claw to hook on to.

        In small arms, combustible-case ammo suffers from most of the problems of caseless ammo: you need a unique gun mechanism (like LSAT) because of the extraction problem and the cartridge is relatively fragile and open to environmental effects (e.g. variations in humidity). Furthermore, if the powder is loose rather than solid, the combustible case has to be strong enough to keep a firm grip on the bullet while the ammo is being violently handled in an MG feed.

      • John Kensington

        Thanks for that clarification.

        Cheers mate, JK

  • Lance

    @ Phil White

    Plastic is a waste if its about cost reduction steel or Aluminum can be used in medium caliber rifle cases the Army did experiment in the 60s with 7.62mm NATO cases made of aluminum. So 5.56mm would be very easy to use.

    Overall Aluminum is light and is better strength to heat than plastic.

    Too me brass or steel is better than both. Tell solders ho cry about a few ounces to join the Navy.

  • WeaponBuilder

    I guess they never heard of the K.I.S.S. principle? The manufacture of something so critical as small arms ammunition shouldn’t be made into an overly complex process, nor do I think it should be dependent upon Oil (polymers) or more exotic materials, or more advanced processes. If anything they should look into teaching better marksmanship, and conservation of ammo!

    Interesting to see a combat patrol comee under fire so they dump 800rds from each MG blindly toward a wooded hillside, along with 6 HE 40mm, and 2+ magazines per soldier… They fire a rocket, and finally get him… One man with a rusty old Mauser and 20 rds holds up the whole squad that spent 4 to 5 thousand rounds, plus grenades & a rocket to kill one old man!

    NO wonder they want lighter ammo to carry more… Marksmanship isn’t exactly a strong suit these days – where fire superiority reigns.

    • B

      A lot of what is fired is suppressive fire to allow movement of our troops, and to force the enemy to keep from moving.
      While the M4s have proven to be a highly accurate weapon platform (as proven by the DOD investigation a few years back into Marines executing Iraq soldiers due to deaths from single hit headshots (which were proven to be hits “from a long distance”)) – their main role is to make the other guy keep their head down and not shoot back.
      Mortars, airstrikes, and lucky hits. That is usually why the enemy dies.
      Just to clarify, absolutely no disrespect to our servicemen and women who lay their lives on the line for our freedoms, but accuracy isn’t really emphasized – so yes, lighter rounds so they can perform the way they were trained would be good.

    • Esh325

      I think you’re drawing rash assumptions. They didn’t specify polymer cased ammo as a replacement for brass. Regardless of how the soldier might be trained, they probably all appreciate lighter weight equipment.

  • B

    Perhaps hard anodized aluminum cartridge cases that have been cryotreated could strong enough and light enough to withstand the pressures generated by 5.56 rounds.
    Cryotreatment has been shown to increase the toughness of the treated metal from heat related distortion. Might be something to check out.

  • I know that Zamak weapons ala Hi-Pointe get a bad rap, however I remember some .38 special ammo that Ree’s Contract services had me qualify with back in the early 90’s which had Zinc Aluminum cases. I don’t know where they got it, but the rounds were lighter than my brass cased winchester ammo and were just as accurate. The ammunition was in a cardboard box that only said “Environmentally Friendly” 125 gr JHP .38 Spec. +P and came 100 rounds a box. I can’t find anything on the ammo, but I used it every 4 months at requal time.

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  • Sam Suggs

    this is nice for special forces who dont mind leaving a clear indicator of their presence however as a standard issue thing its probobly not a good idea unless they want to have sperate training and combat ammunition

  • Sam Suggs

    Its all about how it will handle a hot chanber I think the chaber will heat up more slowly but what do I know. ceramic cases 2013 fingers crossed