I Had A Dream: Modular Polymer Ammunition

Last night I had a dream where I was at the range (many of my dreams start at the range). A friend asked me if a 9mm Luger load with a heavier bullet would shoot more accuracy. I turned around, unziped my range bag and took out pre-primed cases, bullets of the correct weight and a box of compressed powder pellets. I put the powder pellet into the case, screwed in the bullet and then handed the loaded cartridge to my friend.

The concept my unconscious brain come up hinges on having a polymer case with internal screw threads that will break off when the round is fired. The hard copper threads of the bullet should cleanly strip the polymer case threads.

Triple Se7en muzzle loader pellets.

I like the idea of being able to create a custom load on demand is nifty, but this idea is fraught with numerous problems. The bullet seat depth could not be controlled, the cases would need to be pre-primed, compressed powder does not burn as well as uncompressed powder (and powders would need to be developed), bullets would be more expensive and accuracy would not be as good as a conventional loaded round. Don’t expect Steve’s Special Supreme Modular Polymer Rounds to appear on the shelf of your local ammo retailer anytime soon.



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.


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  • Nathaniel

    In fact, I quite suspect ammunition is about to move in the opposite direction: with more components being seen as one element. Handloaders often object to the idea of caseless or plastic-cased ammunition on the grounds that they’re not easy to reload… Overlooking the fact that brass is usually the most expensive component, at least for rifle ammunition, and the fact that properly designed caseless/plastic-cased ammunition would actually be easier to reload (with seating depth being regularly controlled, thanks to solid propellant).

    • JMD

      That idea makes no sense at all. The material properties of polymer wouldn’t allow a polymer case to be resized. Polymer doesn’t have the required plasticity and elasticity properties to make that work. Once it stretches, you can’t just squeeze polymer back into shape with a die like you can with brass.

      Then there’s the issue of what the primer is going to do to the primer pocket and flash hole. Will either still be in a useable condition after the first firing? I really doubt it.

      I would assert that polymer cases are probably not possible to reload even one time.

      I also take objection to your assertion that brass is the most expensive component. Take for instance an unusually expensive cartridge case that costs $1.50 for each case. That price is an intentional exaggeration in expense for most cartridge types, for the sake of argument. Broken down per firing, for a modest 10 cycles (which is fewer than can be reasonably expected from many cartridge types), the price comes to $.15 per case per firing. That’s about half the cost of many premium bullets, and still less than the cost of most “budget-priced” bullets. $.15 is roughly the minimum cost of the amount of powder in one 30-06 cartridge. Take all that into consideration with the fact that most cases DO NOT cost that much per unit, and it becomes quickly apparent that your argument is nonsensical. Most expensive component, indeed.

      For these reasons and more, polymer cases only make sense as a single-use, consumable item, and then only if the total production cost of complete cartridges is significantly lower than that of conventional ammunition. Even in that case, I doubt they’ll ever meet the requirements of people who currently hand load to achieve optimal accuracy for their particular firearm.

      Self-contained metallic cartridges certainly have their limitations, but the technology is highly refined and extremely effective. It will take a tremendous technological advancement to unseat that concept.

      Polymer-cased, semi-cased, and caseless ammunition are like flying cars. Great in theory, extremely difficult in practice, and perpetually “just around the corner” developmentally speaking.

      • Nathaniel

        Such polymers as are being discussed are not highly malleable, like metals, but instead are highly elastic, meaning resizing isn’t necessary.

        High temperature polymers will most likely stand up to the pressure and heat generated by the primer just fine.

        You’re calculations are fallacious: You say that brass is not the most expensive component, and then talk about in order to make it even with the cost of other components, you have to re-use it many times. Brass is definitely the most expensive component, which is precisely why it’s reloaded many times.

        In short, none of your arguments are valid.

    • JMD

      Show me this magic plastic that springs back to it’s original shape well enough to hold proper neck tension on a bullet.

      You do realize the fundamentals of RE-loading, right? Regardless of the cost of brass, it’s going to get reused many times. That’s sort of the point.

      I picked $1.50 as my figure to make a gross exaggeration that your point doesn’t make sense. Even with a VERY expensive case, brass is still not hardly the most expensive component, precisely because it is reusable. The last time I bought 5.56 brass, it cost me $.05 cents (five cents) per piece. Please explain to me how that’s the most expensive component in the process. Even if I only load them once and throw them away after a single firing, they’re still not the most expensive component involved. Even cheap, bulk-purchsed 55 grain FMJ bullets cost $.08 each. In that case, the bullet is 60% more expensive than the case, even with a single use. If I break down the cost per case over the seven uses I’ve gotten so far, then your argument has even less strength.

      Do you have trouble understanding basic arithmetic?

      • JMD

        I mean…your argument here is based on the idea that the grossly inflated $.15 per firing case cost is somehow a larger number than the $.15 worth of powder, or the $.30 bullet. Last I checked .$15 = $.15.

        With a case that has a starting value of of $.42, that lasts only five firings, your argument completely falls apart.

        http://www.midwayusa.com/product/1390176376/winchester-brass-308-winchester

        Broken down, the cases in the link posted would cost just $.084 each. How is $.084 larger than the cost of the projectile or powder needed to complete that cartridge? Please explain to me how $.084 is larger than $.15.

  • This idea is something that would realized long-long time ago.

    (There were some CQ training plastic round be Speer. With primer-only.)

  • Flounder

    LOL I love it! Maybe if someone ever developed a commercial caseless round then it could happen…

  • noob

    After having disclosed the concept, I think there is now a 1 year clock ticking for you to patent it.

    patenting it could actually ease getting the idea to market, since you could offer royalty free licences for people who want to implement it, and nobody can patent troll you for 16 years after you’ve been awarded your patent.

  • Jeff

    “The bullet seat depth could not be controlled”…

    Both the bullet and the plastic shell being cast and injected molded pieces respecitvely could have the threading placed consistently by being part of their respective molds… that said you have as part of those same molds different marks along the outside edge of the casing and bullet; that when screwing in the bullet you line up these different marks to give you a particular bullet seat depth. It might not be perfect, but would give you some ability to get closer to what’s desired.

  • Splodge

    Actually, controlling the seating depth is very simple. Aside from making the solid propellant at such a length were the bullet with stop on top of it at the correct depth, simply producing the bullets with the depth pre-set by the thread itself will work – as long as both the bullets and the cases are consistent, you should have no problems.

  • SpudGun

    I like this idea very much. If I might be so bold as to suggest a couple of tweaks –

    A crimping tool that uses high heat to seal the polymer case around the bullet once it’s been seated.

    Using a compressed powder that is bonded by a weak adhesive – so that once loaded, you just give the cartridge a whack and the powder becomes uncompressed.

    Keep at it, it is a very nifty concept and worth developing.

  • DaveR

    The idea is pretty neat. I would guess that this would be of most interest to hunters and target shooters who are looking to tweak their loads at the shooting bench rather than the reloading bench.

    The downside is that the specialty bullet would limit projectile choices (though you might be able to come up with a way to “thread” conventional bullets). And, as has already been pointed out, pellet-ized powder might prove to be too variable in burn rate to produce consistent accuracy; powder development may become the deciding factor here.

  • I’ve thought of a similar concept many times. However, my idea was to adapt it to bottleneck cartridges. Folks have already come up with polymer bodies combined to metal bases. The problem has been that the necks of the cases cannot always prevent the bullet from being pushed into the case when fed through automatic weapons. The idea would be to mold the case around the projectile, then insert a solid propellant charge, and cap it all off with the metal base. The solid charge would be long enough to prevent the bullet from being pushed down into the case. You could also use some of the non-nitrocellulose propellants devised for HK G11’s caseless cartridges, including tricks like an initial booster charge.

    Along the same lines, I’ve also wondered why semi-caseless cartridges haven’t been tried, basically a solid charge attached to a metal base. This would be like a mini-version of the 120mm rounds used by the M1 tank. The metal base would provide a gas seal and allow for a conventional primer and firing pin. You lose part of the weight in comparison to a full-length case, and the stub base would be easier to extract.

  • Witt Sullivan

    20 some odd years ago, there was a company that produced polymer casings, it may have been the first company to commercially produce them. You could get a reloading press that looked like a hand exerciser that pushed the primer out of one end and pushed the bullet into the casing on the other end. You still had to measure the charge with a scoop or scale, but the rest was sort of revolutionary.
    You could also make your own custom ammo at the bench by using a Lee Loader kit or a Lyman Ideal nutcracker kit.

    • Witt: That was the USAC .38 Special. They used proprietary heel-seated projectiles that snapped into the plastic case. Reportedly, you could resize the cases by boiling them in water.

  • matt

    A system like this all ready exists for metallic reloading, look at Wilson arbor press dies. They’re designed to be used at the range. And the entire idea of a threaded case/bullet is dumb. No one seems to be concerned about bullet set back, or what happens to all those little broken off plastic threads. If you were going to do something like this it would be better to use a heeled bullet like in .41 Colt.

    • JMD

      Regarding the broken threads, they would be trapped against the bore wall by the threads on the projectile, and carried out all together with the projectile.

      The heeled bullet also occurred to me. A threaded base on a heeled bullet with shims to go between the “shoulder” of the bullet and the case mouth could be used to regulate seating depth. Of course, then you give up the ability to use the case mouth for headspacing, so any case design utilizing a heeled bullet would have to be rimmed, as in the illustration above, belted, or a bottle-neck design that can headspace on the shoulder.

      Instead of different sized propellant pellets, perhaps something resembling cordite sticks could be used. Pre-cut to standardized lengths for different cartridges, choose how many sticks to put in the case for different power levels.

      The concept of the bullet having to sheer off threads to leave the case raises serious concerns about chamber pressure, especially in pistol ammunition.

      The whole concept is an interesting “thought exercise”, but it sounds too complicated to ever be a commercial success.

  • Lance

    Kinda pointless for practical operations but fun for the reloader hobbyist. This would make Dillon worry. Still not sold on plastic cases pistol is ok but this wouldn’t be OK for rifle cases.

    • SpudGun

      I don’t see why not, I’ve fired 3″ Magnum shells using plastic hulled ammunition through my shotgun without any adverse effects.

    • Lance

      Well pistol and shotgun ammo is much lower PSI than rifle. Plastic ammo Ive seen in 5.56mm failed badly often losing there necks when shooting. That’s not a bell ringer for plastic cases. Case less is more of a technology Id like to see than plastic cases.

      • SpudGun

        I’m curious Lance, where did you see the failed 5.56mm polymer cartridges? I mean, I’m sure there was a failure, but where exactly did you personally see the failed rounds? I didn’t even know they were on sale.

    • Leonardo

      To clarify, i just thought of the threading part

    • Lance

      Maytag made polymer cased 5.56mm ammo about 4-6 years ago. Ive seen them shot in ARs and AK-101s.

      • SpudGun

        Cool, good for you. I’ve had a look online and can’t for the life of me find this ‘Maytag’ ammunition you’ve mentioned. I found some NATEC reviews but not Maytag. Could you please be kind enough to point me in the direction?

  • Leonardo

    With all honesty, i had this idea about 5 days ago, i’m amazed at this coincidence and in complete shock. Great minds think alike!

  • R

    Great idea.

    Ditch the thread and replace it with a properly located groove on the bullet and ridge inside the mouth of the case – think snap ring and O.D. groove on the bullet.

    Polymers can have plenty of shape memory to momentarily deform and positively snap onto a bullet pressed into the mouth. This solves the setback issue since the groove and ridge are at spec locations.

    Start with something like a half-round ridge and groove. Case can be a few thousandths undersized at the mouth until the bullet is installed which forces it to conform and have the proper overall O.D.

  • Komrad

    I just realized a potential safety issue with polymer ammo. I have two snap-caps that cape with my CZ-75B. They have plastic bodies and are colored black. They are obviously not real ammunition when you look at them in the open, but they could very easily be confused with black polymer cased ammo when doing a chamber check. Obviously you should do a more comprehensive safety check than just opening the chamber far enough to see the color of the case before dry-firing, but not everyone does that.
    The issue could easily be averted by using more colorful snap caps or some of those anodized aluminum bodied ones. I’m just too cheap to buy those when the two free ones work fine.

    • Tinkerer

      They make snap-caps in transparent plastic. That would make very clear their nature.

      Mmh, transparent polymer case ammo…

  • DrDave

    I rather enjoyed the post. Of course it couldn’t work as described, but isn’t it great how you can come up with something crazy in a dream? I have dreams like this regularly. Every time I wake up thinking its the greatest idea in the world; I mean totally convinced. Then after rethinking it (and waking up fully) I recognize the absurdity.

    I’ve recently been messing around with high speed video cameras and also long range shooting (not at the same time). I had a dream that my swarovski spotting scope had a built in high speed camera. The scope had a button that would allow me to watch a shot in slow motion as it was being fired and impacting. In my dream I could exactly correct for the follow-up shot. It was so cool in the dream that when I woke up, I immediately wrote down the idea. Reading my notes a few days later, it made me laugh. Fun idea, but not really a better mouse trap.

    Anyway, fun post. Thanks.

  • james

    i don’t understand why the option of using pelleted powder is not currently offered for reloading..

  • Darth Cossack

    Plastic shotshells work and reload reasonably well, so things aren’t entirely hopeless.

    An additional area of difficulty is in the rim of the cartridge. A plastic flexible enough to obturate and seal the chamber may not be stiff enough to allow for positive extraction.

    I seem to recall an all plastic shotshell that was a two piece affair with a harder plastic rim section. Others had a metal washer the base of the hull was cast around, which might work better for a rimless cartridge.

    Although, perhaps an entirely new cartridge could be designed with the material properties of plastic in mind so such measures would be unnecessary.

    Neck tension is an interesting problem. An adhesive might be able to serve as an alternative, with some kind of minimalist hand press to set seat depth.

    The LSAT could also serve as inspiration.

    A plastic telescoped cartridge could be very cool. The powder pellet accepts the cartridge and provides a shoulder for the base of the bullet, which makes seat depth easy. I imagine it all held together with a folded crimp, just because it makes me smile.

    • Komrad

      Building on your adhesive idea, what if a small iron was used to melt the plastic to the bullet. Obviously, it would need to be far enough below the case neck to not cause deformation, but it could work.

  • Tinkerer

    Considering the availabity of such technologies as: propellant pellets, plastic sabots, etc., I imagine that a straight-walled shaped round with the solid propellant fixed on the hollow base of the cartridge would make a nice caseless ammo -kinda like the old Volcanic ammo from mid-19th century. Think of it as a Minie bullet with the pellet inside the base cavity.

  • John Doe

    When will there be a polymer bullet that won’t screw up your barrel? I think plastics would let the bullet be denser where it needs to be, softer where you want maximum expansion.