Need some ideas for testing brass

OK science - time to pick your brain.

I have several 1000 pieces of brass - to be specific, 9mm luger ammunition brass.

The reloading community argument over which manufacturer makes the " best " brass for reloading has raged on for decades, but in all of the discussions I have read over the years, there’s ZERO science behind any of these opinions.

I’ve got the brass, I’ve got a LOT of free time on my hands.

  1. My question to our DMS science geeks is, is there a non or low toxic way for me to assay LOTS of small samples of brass in my garage without special equipment ( assume no fume hood ) to discover some or all the components and their ratio in the brass alloy? Given this is brass, I am aware that there are some toxic oxides involved - so maybe the approach would require I assemble some sort of fume hood.

  2. Next - is there some easy way to perform a pressure or crush test and get a measurable PSI value to assess the hardness of each case?

  3. Would electrical conductivity give me any useful information?

I’m thinking I want to test the production brass of some 8 different manufacturers and I have between 500 and 1000 pieces of brass per each.

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I’d recommend before starting out to see what’s best is to make sure you know what “best” is.

What makes a brass case useful? Is it how “hard” it is, or how “soft” it is, etc. What about case wall thickness? Is more better? Or as thin as possible? etc

The more hard numbers or ranges of numbers the better.

Also, this seems like something cool to check back on, I really like the idea to science it!

Not an engineer, but I’d did stay at a holiday inn before Ebolaextra.

What about loading rounds with a repeatable load, fire the round then measure the deformation of the brass in circumference and length. Every time you true up the brass the process removes some brass.

Just because Remington might be harder or softer, lighter or heavier, than a Winchester piece of brass doesn’t mean it will hold up better in the real world.

I would measure the amount of brass removed from the true up and squaring. You’re going to be dealing with very small amounts of weight.

Even more fun, just keep reloading the same brass until you don’t feel like it wouldn’t be good to reload it again. See which manufacturer holds up to the most reloads.

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One quality of good pistol brass is that it holds it’s shape well through reuse.

Here is where I’d expect the peanut gallery to bring up the term " once fired brass "…

Part of this study would be to identify that once fired brass is a safety concept rule of thumb, but " good brass " can be safely reloaded several times. It will eventually wear out. Part of the point here is to identify which ammunition manufacturers produce good brass casings for use in private reloading.

In pistol brass, a few conditions are apt to happen with weaker brass, be it an alloy problem, or thinner material or both. You can get case bulge which happens near the base of the brass and is typically a fault of the weapon’s breech not being tight enough or fully supporting the brass walls resulting in a slight ballooning of the brass. This indicates a weakening of the brass and the bulge may prevent chambering which is bad. The second condition found in brass is case run-out, i.e. the reloading of the brass repeatedly has caused the case mouth & neck to flare. As a bullet is pressure fit into the case, a run out case neck / mouth can cause the bullet to seat loosely, or slip entirely down into the case which can cause a miss-feed or cause a dangerous pressure condition to develop when the space for the powder to expand is reduced bringing about an over-pressure condition. And the final failure condition of brass is case failure - when a case ruptures. An inconsistent alloy can cause a weakness in the case. An inconsistent production process can cause a weakness in a case. An accidental overcharge can cause case rupture which may lead to weapon failure & injury. If the brass is too soft, too hard, or inconsistent it can rupture.

So knowing a brass alloy and measuring the hardness of the brass as well as the case wall thickness makes a difference. Knowing the alloy might also allow us to gauge which one is more elastic, coming back into shape with use.

Thus I want to understand what the alloy is and is the alloy consistent across a statistically significant sample of the brass. An inexpensive way to assay and reliably identify the brass alloy will likely be the more difficult challenge here.

I’d like to formulate a pressure / PSI test as well to assign a value to the alloy that will give me some measure of the toughness of the material which will likely indicate it’s expected durability over time. The question will be is the design of the test - how the force is applied - the failure condition - and whether or not the force vector applied is relevant. Doing so without risking anyone’s health & safety and not risking a firearm in this test pretty much prevents doing anything like an intentional over-charge. I’m more thinking of applying a measured pressure to a bunch of cases - say possibly crushing the case head and recording the pressure necessary would be the desired methodology.

My hope is to judge the alloy - what is too hard - what is too soft. Brass does need a certain elasticity as it should ever so slightly expand to seal the firing chamber of the weapon so that most of the force of the powder charge explosion is used in the desired operation of the weapon. Note that this differs from a single shot or revolver and a semi-automatic which depends upon the discharge to cycle the weapon.

One pressure test I can imagine would be to apply known pressure to the neck of the case and measure at which pressure the case neck deforms by 2 thousandths of an inch and does not snap back into shape. This will take into account both the alloy and the case neck thickness together. If this test were applied to a representative sample - say 200 - of the brass. I’d feel pretty confident in my findings. I’d likely be a 2 part test - pounds of force to deflection in a single hit - and apply a consistent force counting the number of applications until deflection / failure.

The question for the easier of the two questions would thus be what device(s) to use to measure crush pressure on the edge of a brass pistol shell.

Traditional cartridge brass is nominally 70% Copper with 30% Zinc added. In the Unified Numbering System (UNS) cartridge brass is grade UNS C26000 in which copper is specified as 68.5-71.5wt%, lead <0.07%, iron <0.05% and zinc the balance. It is noted that cartridge cases are nowadays manufactured from either C26000 or its modifications.

These brass alloy are a single phase alloy, which metallurgically we call "Alpha” phase which has a face centered cubic structure. The solubility of zinc in copper is 32.5% at the solidus temperature of 900˚C and 30% at room temperature. At zinc contents above approximately 38% a new phase forms which we call "Beta” phase which has body centered cubic structure. The alpha phase is suited to cold working but not hot working and the beta phase is suited to hot working and not cold working. Brass forgings which are heated to around 750-800˚C require some beta phase to allow the hot working. The brasses used in cartridge cases are entirely alpha phase and are ideally suited to cold working having superior ductility of the copper-zinc alloys.

C26000 has a melting point around 915˚C and remains as a single phase solid-solution to room temperature.

1.2 Hardness

Hardness can be described as "resistance to indentation” and can be determined in a scientific manner using dedicated hardness testers. Often skilled operators can use workshop techniques such as using resistance to manual filing to work out which material is harder than another however this is only a relative test and in no way scientific.

There are various hardness testing machines such as Rockwell testers which typically use the HRB scale using a 100Kg load on a 1/16” diameter steel ball, Rockwell F or the lighter superficial Rockwell T scale. Brinell hardness testers use a 10mm diameter tungsten ball with test loads of 500Kg to 3000Kg, and Vickers hardness testers use an inverted diamond pyramid with specified dimensions. Upon indentation into the test piece the two diagonals of the diamond indent is measured and averaged and a formula or conversion tables are used to give a hardness in Vickers units HV. Vickers hardness testing is usually divided up into standard Vickers with test loads of 5Kg to 30Kg and microhardness with test loads of 10g to 1Kg. There are other hardness testing units available such as Knoop (HK) which is similar to Vickers except the diamond indenter is elongated. It is noted that Knoop hardness is often favoured by engineers in the USA while Vickers hardness is more favoured by the British colonies.

Each hardness testing method has its uses and limitations. For cartridge cases that are relatively thinwalled it is a requirement that the hardness indent fits onto the brass without deforming the sample under test. For this reason lighter loads and smaller indents offered by Vickers or Knoop microhardness testing are suitable.

1.3 Cartridge Brass Hardness

The hardness of brass has traditionally been discussed in terms relative to its maximum hardness. Publication No.36 by the Copper Development Association (CDA) in the 1960’s show that for cartridge brass full hard is typically 175-185HV and fully annealed cartridge brass is typically 65HV. Other publications also describe soft, ¼ hard, ½ hard and spring hard etc.

In the American systems I note that the hardness of cartridge brass is often reported in HRB, HRF and HR30T scales.

1.4 Grain Size

It is not uncommon to hear people talking about hardness and grain size as if they are the same thing. I often hear people discussing how a material is harder because it has a smaller grain. Textbooks on mechanical metallurgy describe how hardness is more related to tensile strength while grain size is more related to yield strength of a material. Equations such as the Hall-Petch formula relate the yield strength to the grain size of a material. Hardness conversion tables occasionally show the tensile strength of a material at a certain hardness. Often the yield strength (hence grain size) will follow the tensile strength – that is as the yield strength increases (grain size reduces) so does the tensile strength increase however this is a generalisation which must be carefully considered.

I have read reference documents that plot tensile strength against grain size in brass and there is a trend in material which has no prior history. Experience however shows that as a material is used and worked and annealed these trends can become very erratic and therefore commentary about grain size and hardness should be treated with caution.

1.5 Annealing

Annealing is a process where a specific amount of heat energy is applied to brass in order to restore the brass back to its soft relaxed state to increase the ductility and/or toughness. Annealing is a function of time and temperature. A brass which has been cold worked previously has some stored energy in it and therefore response to annealing can be quicker and at a lower temperature than an equivalent section size which has not been worked.

Metallurgists discuss annealing as involving recovery, recrystallization and grain growth stages. In the recovery stage hardness remains relatively constant as some of the original properties of the brass recover, during the recrystallization stage the hardness decreases and continues to decrease (although more gradually) during the grain growth stage. If a sample is over annealed than there is a risk of grain growth with a reduction in mechanical properties.

It should be pointed out that references such the ASM speciality handbook on Copper and Copper Alloys describe how the annealing process is a consequence of all the mechanisms operating, which is dependent on the material, processing history and the annealing procedure.

There are many different methods of applying heat in order to anneal a sample. Larger ovens will of course heat the entire cartridge to the annealing temperature which has the potential to soften the side walls and head area to a point that their mechanical properties are reduced. The other scenario is to anneal a very localised area of the cartridge such as the neck area only. The ASM (American Society METLAB LTD Report number 1231/1B Page 3 of 3 27 June 2017 for Materials) describe how fine grain structures are favoured by fast heating to the annealing temperature and short annealing times.

Flash annealing is the process of quickly heating a small or thin sample to the annealing temperature to minimise heat transfer along the sample.

1.6 Dezincification

Dezincification is a process where zinc is selectively leached out of the brass leaving behind a weaker copper structure. Dezincification occurs under conditions where certain chemical species such as chloride ions, mildly acidic solutions or ammonia-based chemicals attack the brass. Elevated temperatures can accelerate the dezincification process. On a brass sample, fresh dezincification is evident by a pink-coloured structure and with time this turns darker.

Found at.


Interesting read. Do you have a recommendation on how I might perform a brass hardness test in my garage? From long experience, I have witnessed that BLAZER pistol ammunition brass is of a poor quality to reload while Winchester pistol ammunition is far more reliable and durable and tends to hold up to multiple reloads just fine in both 9mm and .40 S&W calibers. Most other brass tends to fall somewhere in between the two brands. Besides a simple cut in half length-wise to measure the specific cartridge wall thicknesses, I’d want to investigate the alloy and hardness of said alloy to get a far more scientific understanding of why.

With a tester…

Got one handy? - I don’t have $700 to throw at this right now.

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Nope. My shop at home is focused on repairing old computers (70s - 80s) and old arcade game boards, so more electronic troubleshooting gear than metal testing.

If you want a test try cutting a cylinder of the various cases measure the diameter and wall thickness. Place the cylinder between parallel faces and squeeze, plot the force displacement curve.
Compare the results.
Anneal and repeat.

This guy has done some interesting tests on brass. My guess is they all get the standard brass and it all meets the same specifications for their intended applications. Apparently nickel cases don’t last very long at all

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It would have been interesting to see if nickel 45 cases had any variance in life, since the failure mode is different, and what the failure mode would have been if the pockets were occasionally reamed.

Those articles are a good start - I’d have to find a range that would allow me to reload on-range and I’d want to use a revolver as well so that I wasn’t chasing ejected rounds. ( OH NO - a reason to buy a gun!!! - But honey - it’s for a safety test. :slight_smile: ) Actually - it’s likely that argument would work. Seeing documentation, as limited as a test as it is, on Nickel plated brass having 1/3rd the reloading life of brass is compelling.

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