Future of Cartridge Case Materials

Recently had multiple people ask me the question of what is the future of small and medium cartridge case materials. I’ve have been bearish plastic for a number of reasons and been bullish on steel.

What are you guys thinking? Military and civilian?

Arrow Tech

https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2019/armament/Lemay_SA4.pdf

Jay

Untill they invent a plastic that will not melt in a red-hot chamber I’ll go with steel.

My best guess would be: Shell Shock Technologies for civilian, with; ‘reasonable,’ case profile.

The SST stainless / nickel cases would be the way to go if they have any notion of reloading the cases multiple times. The fact that they are 30% lighter than brass, disperse heat more eficiently, cost less than brass, resist extreme cold, handle higher pressures, and are reloadable dozens of times makes them the best in my opinion. If environmental concerns become relevant, then the SST metal cases are also cleaner than plastic equivalents (we know how the military loves to burn huge mounds of ammo in the field while deployed). I was amazed that early on in the SST retail offering of 9mm brass that they were already less expensive than Starline brass. The cost-savings should scale through all calibers.

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At the risk of stating the obvious, I think for military use (non-reloadable) it will be driven by cost and weight. Obviously, brass is not good for either of those.

Steel is good for cost, but not so much for weight (not much better than brass). Plastic is much better for weight and might also be very good for cost if a solution can be injection molded (like CT ammo). I have to think that molded CT cases would be a fraction of the cost of a drawn metal case (brass or steel) in serial production. But these still need more development (which costs $$$).

In the interim, I think hybrid cases might become mainstream for military SAA. By hybrid I mean two or more materials combined (metal/polymer like True Velocity or metal/metal like Shell Shock Technologies). This should be the quickest way to save weight since properties can be tailored for each section of the cartridge case without radical changes like CT ammo.

It doesn’t look like SST does any bottle-necked rifle cases and I have not seen any indication that they are pursuing military contracts. I saw that SIG is promoting a steel/brass case for the 6.8, but I don’t see that as much more than a potential cost savings (carbon steel is about 8% less dense than cartridge brass, so only a slight weight saving). It seems like a high-strength aluminum head (like SST) combined with a steel or polymer case body would give the best weight savings without too much development.

One potential roadblock to hybrid cases is separation of the pieces. It will be interesting to see how this plays out under harsh military conditions.

SST currently produces 5.56 and they say that 7.62x51 is coming soon. My angle on their stainless / nickel cases being a better choice than plastic stems from the notion that U.S. taxpayers could save a tremendous amount of money by using a case type that would be indefinitely reusable, as in dozens of times. Obviously all cases could not be recovered at all times, but if even 50% of them were, it would make the higher cost of stainless vs plastic more palatable, given that they could be sold as surplus cases at the very least. Not that the military has a history of being cost-conscious.

The Feb-2017 Shooting Sports USA magazine report, pages 14-19, state that an average of 10 empty SST 9mm cases weigh 29.7 grains whereas an average of 10 empty brass 9mm cases weigh 58.8gr. That is far more than an 8% weight savings over brass. What the savings would be for larger rifle cases is TBD.

Perhaps because the nickel-steel case body is substantially stronger than brass, less material is needed to obtain even higher strengths - yielding the far greater weight savings than comparing a cubic-centimeter of brass to nickel-steel.

RangerJoe, that’s because SST’s cases use a nickel plated aluminum alloy head (2.7 g/cc), not steel (7.9 g/cc). The body of the case is almost certainly stainless steel (what they call “nickel alloy”), but most of the weight is in the head. See below from the Shell Shock site:


For reference below are the densities of a few materials that might be used for cartridge cases (in grams per cubic centimeter - water is 1.0 g/cc):
Polymers (aka, plastics, including fiber-filled): 0.9 - 2.1 g/cc
Aluminum: 2.7 g/cc
Steel (including stainless): 7.7 - 8.0 g/cc
Cartridge brass (70Cu-30Zn): 8.5 g/cc

Matt, that’s interesting that SST is producing rifle cases. I didn’t see that on their website, but it certainly seems like a great step forward. Do you know if they have gone after any military development contracts?

I wonder how many SAA cases the military recovers? And do they sell them off as surplus for reloading? I know they reload large caliber artillery and naval gun cases, but I wonder if the military ever reloads SAA cases other than match ammo (for something like Camp Perry)?

All:

Thanks for the feedback! Great discussion. You guys rock!

SST and any bi-metal or partial plastic is RISK. The USG will spend the next several years proving out the 6.8. Commercial might leapfrog over the USG, however I would be skeptical that any of the majors would incur the expense and risk. Winchester appears to be in the best overall corporate shape, however they re-define conservative.

A straight steel 9mm would be cheaper than SST. For a 1 shot and scrap application - what is wrong with it?

Jay

Jay assuming the straight steel your talking about would be the same as the commonly available current Russian / Chinese production steel cased ammunition? My understanding is that it is hard on the / our weapons causing higher breakage and wear-out rates.
Perhaps some of this is chamber tolerances or parts design strength? AR vs AK?
I’m sure others can provide better feedback on this factor.

Pete - yes hard on weapons - but how hard?

See attached old ATK presentation.50 cal & 556 steel.pdf (632.4 KB)

Best of my knowledge all the R&D was cut to the bone with the last contract - 2013, because they bid so low and had to announce a $400M loss. The $800M/year maximum for the Army PRIME contract, ends up being closer to $650M all in USG, commercial and export. If I had to guess (Screaming Wild A** Guess -SWAG ) probably $400M all USG and $200M commercial and export.

Jay

We should not overlook:
The first experiments with steel cases were done toward the end of the 19th century (Prof. Hebler, for example) with a view to obtain lighter cases (on the “double strength means half wall thickness” assumption). It did not work out as planned, because of stuck cases in the chamber, due to steel elasticity is different from brass.
Germany and the Soviet Union “embraced” steel cases solely because of their lack of brass available. At least for Germany it is clear that the drawbacks of a much more complex production process (new equipment for heat treating at much higher temperatures, complete re-parkerizing between each drawing step) was accepted because of the lack of brass. No wonder Yugoslavia got rid of steel cases as soon as possible and Finland -as far as I know- rejected them from the start. CSSR and GDR, for example, did not have that choice and continued with steel cases.
On the other hand, Germany and in particular the Soviet Union managed to produce steel cased amunition that achieved a level of reliability on par with brass cased ammunition. There is in my view no indication that steel cased ammunition is “harder” on weapons, causing more “breakages”. Why should it, unless loaded to unsafe pressures? Never heard anybody saying that an AK or PKM would have a longer life if only fired using brass cased ammunition. The steel for cases is of deep draw quality, the same as used for automobile bodies. Its much less tougher than barrel steel and in addition coated (copper, laquer, polymer).
Now we have a new era, where steel is not used because of any lack of brass, but to make use of new technologies to achieve more robust cases or make production less expensive. We shall see whether these goals will be actually achieved. The Russians, having mastered steel case technology for decades and having their factories set up, of course continue to offer conventional steel cased ammunition.

Peelen - one small comment, probably not important at all, but thought it worth a mention. Finland DID produce at least one run of 9 mm Parabellum with steel case, in 1943. Headstamp is “SO43 9.” which is the same as Sako’s headstamp for brass-case 9 mm that year. I don’t know what, if any, the finish on the case is. Mine looks almost like plain steel - a very shiny grey color. The bullet is non-magnetic GM FMJ RN, primer is brass with what appears, with a strong, lighted magnifier, a dark grey (not black) primer seal, which I have never seen on another Finnish 9 mm round.

I suspect it was a one-time issue round. If experimental, I doubt I would have ever acquired one for my collection.

John Moss

If I remember correctly Finland also made a 7.62x54R steel case. (maybe only for testing if they are able to if neccessary)