Future Firearms Ammunition Technology 001: Aluminum Cased Ammunition – Lightening the Load, Pt. 1

Aluminum cased rounds, left to right: .30 T65 Light Rifle aluminum experimental, .280/30 British aluminum experimental, 6x50mm SAW aluminum experimental, 9.53x76mm Winchester quadruple flechette, .330 Amron Aerojet triple flechette. Today, aluminum cases are only used in low pressure applications, like the Omark Industries short range training round on the far right.

The metallic cartridge case was invented in the 1840s, and – starting in the 1860s – its military application brought with it a host of of advantages for the soldier: Now, ammunition was self-contained, weatherproof, and durable. Yet, despite it being a massive advance, the metallic cartridge wasn’t an across the board triumph. With the addition of a metal case, ammunition became heavier, and cost more to manufacture. In the early days of metallic cartridges, military weapons were slow to fire, and fired heavy bullets that made up the overwhelming percentage of mass of the ammunition, so this advantage was small. Ironically, though, the metallic cartridge allowed the invention of faster firing designs that expended ammunition more quickly, and as ammunition caliber shrunk and average bullet weight dropped, the percentage of mass contained in the metallic case grew.

With the .30-06 caliber of 1906, almost 50% of the weight of ammunition carried by the soldier was in metallic cartridge cases that had no effect on the enemy at all, and were just thrown away after firing. In the late 1940s, after two world wars and a massive expenditure of lives and resources, nations began to explore ways to reduce the weight carried by the soldier, starting with the metallic case.

We will explore other potential ways to reduce weight, but today we’ll look at the concept of a metallic case made of aluminum, rather than brass or steel. Aluminum is far less dense than either of those materials (2.71 g/cm^3 versus 8.5 g/cm^3 for cartridge brass, and 7.85 g/cm^3 for mild steel), and so it made a natural first candidate for a drop-in replacement for the traditional metallic case. The 68% lighter case material (vs. brass) could lead to a reduction in ammunition weight of 25-35%, and the use of less-strategic aluminum could save copper resources in the event of a major war.

Aluminum, though, has some problems as a cartridge case. Weaker than brass or steel, the material is also subject in the application of a high pressure small arm to a phenomenon known as “burn through”, where the case is punctured by high pressure gases, possibly due to melting or burning. In lower pressure rounds like pistol ammunition, burn-through is not a problem, but in the 50-60,000 PSI range of a rifle round, this problem is so severe that aluminum cases have never caught on, despite their obvious advantages versus brass and steel.

Aluminum cased ammunition may be down, but it’s not out. New alloys, and different ammunition configurations could allow a resurgence of the idea, but to me the most likely application for aluminum in modern ammunition cases is as the base of a composite polymer-metallic case, which we’ll explore in the next episode!

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.


  • mechamaster

    It is possible to manufacture composite nanoceramic or carbon-nanotube shell in the next decade ?

    • PK

      Neither of those would seem to have the needed properties for gas sealing. Has to be malleable, relatively tough, and so forth, not brittle or porous.

  • Giolli Joker

    330 Amron Aerojet?
    Is it sort of a .338 Lapua loaded with flechettes?

    • Sorta. Yeah. Except .338 Lapua didn’t exist at the time, but they’re not far off.

  • mig1nc

    Aluminum has a relatively high coefficient of friction. More than double brass. And even more than steel. I would imagine that for military grade reliability you’d need fluted chambers or a coating or something to enhance extraction. But aluminum case ammo doesn’t do well with fluted chambers.

    • Kivaari

      The friction from CCI blazer was enough that they would not function in HK MP5 SMGs. We bought a couple cases and hoped to use them for training. They failed with some cases falling into the action

  • Major Tom

    And what about the CT ammo currently being built for the LSAT program? How would aluminum alloys compare to that?

    • Patience…

      • Major Tom

        I can wait then. Sounds like you got something REAL good.

        • Seven more articles of this type are already written and scheduled for next week. 🙂

  • Tony Williams

    Aluminium alloy cases are in US service in two high-pressure cannon calibres: the 30×173 fired by the GAU-8/A in the A-10 aircraft, and the 30x113B fired by the M230 Chain Gun attached to the AH-64 Apache helo. In both cases, the aircraft carry a considerable ammo load so the weight saving is significant.

    I suspect that the main problem with using such cases with small arms is the production cost. I recall that the alloy-cased version of one experimental US small-arms round (probably the 5.56mm FABRL, but it might have been the 6mm SAW) the case was lined inside with some (polymer, IIRC) material to prevent burn-through.

    • Most aluminum cased pistol rounds are actually less expensive than brass; reduced cost is a selling point for CCI Blazer, for example.

      • Tony Williams

        Yes, but treating or lining the cases to withstand high pressures without burn-through is unlikely to be cheap – or we’d have been using such ammo for years, given the high priority of reducing infantry loads.

      • Kivaari

        I saw a S&W M15 destroyed by CCI Blazer ammunition. The case failed and the aluminum cut like a plasma cutter ruining the cylinder.

        • “Hello, is this CCI Customer Service? I’d like to speak with someone in your ‘replacing my handgun so I don’t have to sue you for a bajillion dollars’ department.”

          • Kivaari

            CCI had S&W repair the gun. That was with low pressure .38 Special ammunition, so it can happen without reaching the 50-60,000 psi.

      • supergun

        Any wear or tear on the pistol in using aluminum? I see 9mm in aluminum pretty cheap.

        • No problems that I’ve ever experienced; pistol barrel/action steel is pretty sturdy stuff.

          • supergun


    • Christian Hedegaard-Schou

      Aren’t these guns true chain-guns as well (I know the M230 is), meaning if the round fails, or doesn’t fire, or a number of other things, they’re just extracted and ejected like normal anyways?

      Maybe burn-through isn’t nearly as big of a problem in actions like those.

      • It is still an issue in aircraft cannon, but they figured the massive weight savings was a far more significant tradeoff. Plus, an aircraft can fly away home at several hundred miles an hour if their cannon fails. That really isn’t an option for an infantryman.

    • That’s correct, it’s used in larger cannon calibers (article length restrictions prevented me from mentioning those).

      Both the 5.56mm FABRL and 6mm SAW had variants with flexible internal elements (FIEs) to prevent burn-through.

    • Gary Kirk

      And chamber pressures are relatively equal to that of the 5.56.. 50-52K psi, but, the rim of said cartridges is a whole Hell of a lot thicker. Reducing failure to extract problems..

  • Slim934

    Didn’t you guys recently run that story about ShellShock technologies new case? That’s an aluminum case with a nickel coating. How could you not mention that here?

    • “In lower pressure rounds like pistol ammunition, burn-through is not a problem”

      Pretty much all the mention they require…

      • Kivaari

        As I mentioned above I saw burn through with .38 Special. I no longer buy any CCI Blazer aluminum cased ammunition. That gone on for nearly 30 years. That and the failure to work in the MP5 was enough for me to swear off the stuff. If it has gotten better, I don’t want to be the test bed for more damage or simply not working well. I’ve used Blazer brass and it worked fine and had some of the cleanest burn I’ve ever seen.

    • Brian

      That has an aluminum head only the rest of the case is a stainless steel alloy.

  • Russian Troll Spetsnaz

    I stood on the first Afghan target I had ever assaulted looking at an AK we had just taken off a body of a man who had decided to fight us.

    It was stamped “1953” and I thought to myself that at that point in time that rifle had been in combat for at least 40 years, with little to no maintenance, and was just as deadly that day as the day it rolled off the manufacturing line in Russia.

    I thought back to 2002, right before deploying to Kuwait in preparation of the invasion of Iraq. I had the opportunity to do the first non-bias “official” testing on the AK-47 for the Department of Defense (DOD) and Special Operations Command (SOCOM).

    Up to that point in time no data could be located on the performance of the AK, where the DOD had officially tested it. After I finished that week of testing, it forever changed the way I look at the AK rifle and I came to the conclusion that the AK was the best-engineered rifle in history.

    Since that time, I have used, carried and taught the AK extensively.. It was my choice of weapon during the years I spent fighting in the Global War on Terror and would be to this day.

    During the DOD/SOCOM testing, we exploded all the myths associated with the AK such as accuracy, ergonomics, heat, etc.. We confirmed that the AK did in fact have incredible reliability. We proved that the rifle was well within the parameters of accuracy, the ergonomics just simply needed to be learned and understood, and that it was an incredible feat of engineering.

    To understand the rifle, you have to understand the mind set of the men who designed her. Every Russian felt the effects of the war with Germany. Over 20 million Russians died during the war and many soldiers starved or froze on the Eastern Front.

    Kalashnikov himself was wounded on the Eastern Front and saw the meat grinder first hand. To assume that every single portion of the AK was not thoroughly thought out is naïve at best. They knew what made a good battle rifle, because they had personal and first hand accounts of the most destructive war the world had ever seen.

    What I like to call “Team Kalashnikov” would have all been men who fought against the finest mechanized army the world had ever seen, the German blitzkrieg army. Those same men would have seen friends and family die from starvation and cold, in no small part due to lack of supplies. They would have had burned into their brains that above all, weapons must work, even if logistics are cut off and no maintenance materials are available. Weapons must be easy to fix, or its parts easy to fabricate, and continue to fire even in the harshest of conditions.

    One of the brightest mechanical engineers that I know once said to me “Any idiot can come up with a complicated solution to a problem. But it takes a genius to come up with a simple solution to a complicated problem.” I believe that simplicity is the spirit of the AK-47.

    The AK is an incredible achievement of engineering that has withstood the test of time and I would argue that it’s the most ergonomic, best thought-out, and least-understood rifle today.

    I think it’s fair to say that the men who experienced the horrors of the Eastern Front would have first and foremost wanted reliability in the most extreme circumstances. We’re not just talking about dirt, grime and wear but temperature extremes, hard unrelenting use, little or no lubricant, no solvent, no cleaning supplies and unreliable ammo.

    The rifle would need to hold enough bullets that it could be an effective platform for fire suppression and a reduced rate of automatic fire so that a single man could control it.

    The rifle would need to be accurate out to 300 meters and we proved in our testing that the 7.62×39 fired from an AK was more than adequate. More importantly, the rifle would need to be accurate even in the hands of a minimally-trained fighter, so the ergonomics would facilitate accuracy in fire, especially under stress.

    Any look at current news events, history or use of the AK-47 itself confirms all of the above. But American gun owners, whose experience of a rifle consists of limited range shooting, followed by cleaning, might miss the profound truth of the AK.

    Reliability is no bullshit. When you run your rifle through the ringer, as happens on almost any battlefront, you live and die based on how relentlessly your rifle does it’s job.

    If that’s your definition, as it is mine, than the AK-47 is your assault rifle.

    The AK47 — Best Fighting Rifle in History
    by Jeff Kirkham

  • Pedenzo

    My Wife was a ballistics technician working for CCI/Speer in the 80’s. She remembers the development work done on an aluminum cased 5.56 for the gubminmunt, it was all hush hush at the time. Well, somehow, one of the completed rounds was spirited off plant….and is now sitting on my shelf in my reloading room…..

  • It might, or it might not. Too early to tell. These articles are very short, constrained by a word limit, so I cannot mention every possible development. They have to be an introduction to the ideas, only.

  • guest

    problem with alu cases, as if they don’t have enough problems to begin with, is manufacture. They can be extruded just like soda cans and what not, but each step requires heat treating to avoid premature fatigue. And even once that’s done it has to be coated just like steel cases to avoid corrosion and what’s worse: galvanic currents that with a few drops of salt and given the cartridge has a brass bullet will chew trough it in no time.
    Plus potential case failure in the chamber, plus cost, it’s just a never-ending list of problems. And those few percents of weight it saves in overall gear weight of say and equipped soldier can be saved in other ways with less risk.

    As with many other things alu cases (or composite/plastic cases) have to present decisive advantages that outweight the disadvantages AND the cost/difficulty of transition from “old” to “new” ammo, and that with a clear margin. Which is exactly why no army anywhere is in no rush to dump steel/brass cases.

  • jerry young

    I reload and as far as I know aluminum and steel cases are not re loadable at least not at home they kind of fall in line with berdan primed cases unless you have the proper equipment you can’t reload them, I did hear some mumbling about reloading equipment for these cases but haven’t seen anything on the market for the home re-loader yet, I prefer not to waste money on non reusable cased ammo yes it’s cheaper and aluminum is lighter but again throw away and I feel that if I own a gun if I don’t already reload that caliber I soon will, another problem I have with aluminum cased ammo is back in the 70’s when blazer came out with aluminum cased ammo at least when I was first subjected to it it was unreliable and wouldn’t run through anything we had short of firing a single shot and manually loading the next round in a semi auto it did function in revolvers maybe it’s better now I don’t know! If you don’t reload or are stockpiling for when TSHTF and want cheap ammo it would be better than no ammo, I no longer carry large quantities of ammo into battle and carry just enough for hunting so weight isn’t an issue for me, that’s just my opinion!

  • Nicholas Trueblood

    it would jam most bold actions similar to steel cased ammo. Also psi might suffer since you have to sacrifice powder to make the case thicker to resist cracking or underpower the powder for a normal thickness. either way, not cool. Remember the rock test on the aluminum fords?

  • georgesteele

    You wrote: “despite it being a massive advance, the metallic cartridge wasn’t an across the board triumph. With the addition of a metal case, ammunition became heavier, and cost more to manufacture” On cost, I’d agree – but not heavier; a typical American Long Rifle, firing 1 oz ball loaded over 1/4 oz of black powder, had a per-round weight of 1 1/4 oz, not counting the patch or percussion cap, nor the weight of the powder horn; a .30-06, at less than an ounce, was lighter – ~3 lbs instead of 4.3 for 50 rounds of carry weight. As for the cost, you’d have to factor in the first cost of the cartridge even if you reloaded, and unless you were casting bullets (which would cost 60% less than ball, because the bullets were far lighter) the bullets would fetch a premium as well. But the range extension out to 500 yards and beyond would probably be worth it. The buffalo were exterminated largely with .50-90 Sharps-type rifles, which were metallic cartridge rounds AND heavy – which, to be fair, makes your case closer – about a wash on weight. It was said that at the prevailing cost of hides and the cost of the big Sharps cartridges, that you had to bring a buffalo down with one shot, or your profit was lost in the ammunition cost. But the rate of fire was at least 4 times faster than for muzzle loaders.