How to Make Brass

Having started handloading, I was curious as to how metallic cartridge brass is made.  A quick search brought up an informative link. One poster made a few interesting comments:

The necking operation on cases is done with an external forming die, not unlike a resizing die. It generally takes two to three progressive steps, with the incoming parts prelubricated and dried. Before the necking operation, the cases body has to be annealed and pickled (washing in dilute acid to clean the anneal carbon and to etch the surface), then washed in a lubricant and dried.

There is no internal profile mandrel for the shoulder and neck angle, but there is a sizing mandrel which is pulled out through the mouth of the case after necking to make sure the ID of the case mouth is correct. Some processes pull the sizing mandrel out of the case mouth while the case is still in the necking die, as this gives a much more precise ID and OD of the case mouth, but the amount of metal working required results in very low tool life and further work hardening of the case mouth.

In any case, the case goes through “neck and mouth” annealing after the tapering operation to relieve the stress built up from the necking operation, to soften the neck so it can “obdurate” or seal the chamber against blow back, and to soften the mouth so when it is crimped to the bullet, stress cracks do not develop.

In the US military production, the neck and mouth anneal “corona” or annealing mark must be left as proof that the anneal was performed. For commercial brass and most other countries’ military brass, this proof is not required, so the brass is pickled after the necking operation. That is the main reason US military brass is normally not as pretty as everyone elses, but it is generally much better structurally.

Just a few clarifications of how ammunition cases are made. First, almost all brass cased ammo, if not all, is made by the drawing process. The only extrusion process I am aware of is for the aluminum cases made by the boys in Idaho, and that is a very special process. The cases are formed at very high speed so the metal does not have time to work harden. Special presses and special knowledge are required.

As to brass case making equipment, it is readily available. Most of the major manufacturers in the USA us surplus ordnance factory equipment from WWII. This machinery was very heavily built and lasts forever. Even the US Army plant LCAAP still uses a lot of this equipment, though they have spent a great deal of money in the past 10 years on new machinery and new processes.

If you want to go into the case making business, let me know. We have quite a bit of machinery available, and we are constantly getting more in. The basis process is start from a purchases cup, draw it to length through two to four draws, trim is, head it once or twice, turn the head and extractor groove, anneal the body, taper for rifle cases, and final trim. Depending on what caliber you are making, the process is either simpler of much more complicated.

It’s not cheap to get into this business, and we are at the peak of the market now. If you start making cases now, you could be bankrupt in a year if the wars in Iraq and Afghanistan wind down. There will be a lot of surplus capacity on the market when that happens. That said, if you have the money, we will sell you the equipment and the know how.

Just a little more on how cartridge cases are manufactured. Worldwide, there are two similar but distinctive processes used to make most of the small caliber brass cased ammo. I am leaving out the aluminum case manufacturing as that is a unique process developed and used by only one major company, and it wouldn’t be fair to them to tell the little that I do know about the process.

What I refer to as the US process starts from coiled 70%cu/30%zn brass (cartridge brass) that is annealed, then fed into a double acting press where a round blank is cut, then a cupping punch pushes the blank into and through a forming die. The formed cup pops out the other side, where it is collected, washed, annealed, pickled, lubricated, and dried.

Cups are generally formed in multiple tooled die sets, with each stroke making five or more cups. The more cups made per stroke, the less percentage of scrap generated and the higher the production rate.

The cups are fed into the initial draw press, where a punch pushes them through a die stack, typically three dies high. The dies are normally lubricated with a constant flow, and it is common to put spacers between the dies with channels to allow the lube to flow to all of the dies during the forming. At the bottom of the die stack is a stripper made up of steel jaws and a spring to hold it together. The stripper generally mates into a conical stripper ring to add a bit of closing force as the drawn case component is pulled from the punch.

Additional draws are performed as required to reach the final o.d. and length, and in some cases, an interdraw anneal is performed to relieve the stress built up by the cold working in the draws. Generally, the components are washed before anneal to prevent the lubricant being baked onto the surface, and after the anneal, the components are pickled in a mild acid bath, then washed and dried. The acid bath can remove the carbon that would be on the component if it had not been washed prior to the anneal, but the pickling bath gets dirty quick as a result, and a carbon residue will often be left in and on the cup. Draws do not like dirty cups!

The pickling wash is a very critical step in the process. After the annealing, the grain size of the brass has grown, and the pickling etches out between the fully formed grains, leaving a microscopically rough surface. This rough surface helps to carry the drawing lubricant through the draws, reducing the surface friction between the brass and the draw dies.

On the subject of draw tooling, most high production operations use carbide dies for the forming operations. Punches are mostly steel, though you will find some unique metals being used in the heading operation, especially for the stem, or internal mandrel. When using steel, brass tends to load up on the surface during cold working, even with a flood of lubricant. The loading of brass onto the working surface of punches and steel dies will cause case scratching, high draw loads, and host of other undesirable problems. The loading can be reduced or eliminated by flash chroming the draw punches. Dies are not typically chrome plated as they are frequently polished or otherwise reworked (it is common practice to take the third die in a die stack, once it has worn our or become scratched, and rework it to the dimensions of the second die in the stack, and so on. This reduces the tooling costs and inventory required to support a production operation).

In modern production, such as for 5.56mm cases, the interdraw anneal has been eliminated. For 7.62mm, an interdraw anneal is still in general use.

After the final draw, the component is trimmed to length. Historically the trim is made on dedicated lathes, using either a pointed tool or a rolling cutter wheel. The use of pinch trimming has become much more common in the process as it can be combined into a drawing operation, eliminating a machine and a process step.

Following final draw and trim, the component is washed and dried. Some processes apply a light lubricant prior to heading, or the component is not washed after draw and the draw lube dries on the case. Generally, the drawn part needs to be dry when it goes into heading as moisture on the heading bunter can cause distortion in the primer pocket during the heading operation.

Heading is generally performed on a horizontal toggle press, and most heading presses head one part per stroke. In the past, heads were formed in two steps, with a first step partially forming the primer pocket and also flattening the base of the draw component. This step is called by many names including bunting, pocketing, flattening, pre-pocket, etc. The second step forms the finished primer pocket and stamps on the headstamp, which can indicate the manufacturer, plant, year, and a host of other info. The US 5.56mm ammo from LCAAP made on the high speed equipment for years displayed a series of dots that were binary code for the station number the case was made on.

This second step is called heading, pocketing, bunting, etc., so it is not always clear what is being discussed unless you clarify the terms. The heading bunters can be made as one piece or two pieces where the pocket punch and the headstamp section can be separated. The headstamp can be formed on the bunter face by engraving (not easy or pretty), EDM (easy and pretty), or by a process called hobbing where a hobbing punch is used to form the bunter using a hydraulic press. Hobbing has the advantage of workhardening the bunter during the forming process, but EDM’s advantages have pretty much displaced hobbing.

The typical US heading operation forms a flange on around the head of the case as a result of the metal flow during the heading. Metal flow is critical to the internal hardening of the head of the case, and without proper flow, the primers have a tendency to fall out with regularity when fired. If you section a case head after heading, polish the surface, and etch it with acid, you can see the flow lines of the metal grains resulting from the heading. If the closed bottom of the drawn component is not fairly flat internally, the heading bunter can displace a plug of metal from the bottom before impacting the internal heading stem or mandrel, and little or no cold work of the head material will occur, and the head’s internal hardness will be too low to hold the primer or prevent other distortions during firing. To prevent this from occurring, the cupping tooling can be changed to reduce the crowning of the cup, or a flattening step can be used prior to final heading.

Internally the case is supported during heading using a mandrel or stem that has a profile that matches the internal profile of the post headed case. The stems can be of hardened steel or other dense, non-ductile metal. Ferrotic has been used with some success for these parts.

After heading is complete, the case is headturned on a dedicated lathe using a formed cutting tool that replicates the finished head form, including the chamber on the case head rim, the head diameter, the extractor groove, and the angle leading up to the case body. The cutting tools can be profiles ground into straight tool steel or profiles ground into round washers of tool steel. The round style cutters have the advantage of being easily resharpened, and they can be resharpened numerous times.

Following head turn, the cases are washed, body annealed, pickled, lubricated, and dried. The tapering of the case and the forming of the shoulder and neck can be done on horizontal taper presses, which are not common in large manufacturing operations, or on vertical presses with indexing table. The indexing table allows for multiple tapering steps on one press, and can include high speed milling spindles to trim the cases to final length before they are ejected from the press.

Following the tapering operation, the cases are washed, then neck and mouth annealed. For US military cases, the anneal corona is left in place as proof.

The flash hole in the primer pocket is typically pierced using a punch and mandrel die. In military operations and high volume commercial production, this is done at the primer inserting machine, but for case only manufacturers or for component sales, the cases can be pierced on dedicated punch presses. Failure to pierce a case is a critical defect in military ammunition, so redundant inspections are performed to assure that the flash hole is present.

The prior piece on US manufacturing process did not address the 5.56mm manufacturing at LCAAP. Back during the early 1970’s, a program called SCAMP (small caliber ammunition modernization program) was finally put into production. The basis model for case, bullet, priming, and loading was 24 station rotary turrets turning at 50 rpm for theoretical outputs of 1200 parts per minute. LCAAP has multiples lines for each component.

In order to reduce both capital cost and complexity, the SCAMP case making systems had some shortcuts in the process. Only two draws are used, with no interdraw anneal, and the final draw includes a pinch trim for the drawn part. The components are carried through the system in silicon bronze clips mounted on RC60 chain, and each process step (1st draw, 2nd draw, heading, headturn, piercing, 1st taper, 2nd taper, and final trim) are 24 station presses. A cup entering first draw at Station 1 will exit final trim from Station 1, and station identity is maintained through all the process steps including the washes and anneals.

Following the headturning and piercing, the cases are washed, annealed, and lubricated before going through tapering and final trimming. After final trim, the cases are washed, then neck and mouth annealed. A high speed gaging system is used to gage all critical dimensions and some surface flaws before the cases are ejected from the manufacturing system.

The truncated 5.56mm process operates very close to the theoretical limits of cold drawing from brass, and it took some time to fine tune the process to ensure that the cases produced were acceptable. That said, there is no competing system in the world that can produce 5.56mm at the rate produced at LCAAP.

As mentioned at the start, the other process commonly found is what I call the European Process. Manufacturing plants around the world use either the US Process or the European Process, depending on the sphere of influence under which that country falls. Reflecting the rather fluid states of influence, it is not uncommon to find both processes in use making different calibers of ammunition reflecting the real politic of the era the lines were installed.

I was raised on the US Process, and I have spent most of my life working with systems based on this process, but I honestly feel the the European Process is the better of the two. It flows more logically and is metallurgically more sound. Both processes make good or bad parts, but I have found the Eurpoean approach to be much more forgiving.

As in the US approach, most of the European Process is based on blanked and drawn cups as the input material. Through this step, the process is the same as the US Process.

That said, there are several systems in use around the world that cut and form cups from wire, using a multiple die, multiple blow header to form a cup, rather than forming the cup from coiled strip.

The big advantage of using brass wire as the input material is the lower cost of manufacture of the wire versus the strip, and the much lower scrap percentage of wire based cups versus strip bases cups. In the end, though, the main concern is producibility, and I have been in several plants in various parts of the world that had the machinery to make cups from wire, but they could not buy wire of sufficient quality to make ammunition. As a result, there are several heading machines to produce cups from wire sitting idle in plants from South America to the Middle East.

The case making process starts with cups, either blanked & cupped, or headed, which had been annealed and pickled, and passes them through a series of draws. The early European processes tended to dedicate one machine to one step, which resulted in a lot more machines and a lot slower production rate. Over the past thirty years or so, the Euro process has been refined and speeded up, so today, they are the best source of new machinery in the world.

Current technology would see the case cup enter a press where the draws and pinch trim were performed, the cases removed, cleaned, annealed, pickled, and dried, then re-fed into the same press but in later stations, where they would be headed, tapered, and pierced. For higher output rates, the process would be split, with the drawing and pinch trimming performed on a duplex tooled press so that two parts were made per stroke on that press, and then the annealed parts would be fed into a heading, tapering, and piercing press that made two parts per stroke. The “standard” stroke rate for new presses is 120 strokes per minute, so you could either make 120 or 240 ppm, depending on which approach was taken.

Note that by annealing the parts after the final draw and before the heading and tapering, a process step has been removed. Body anneal is not required, as the whole drawn case was annealed before the heading. The heading can now cold work the case head without effecting the anneal of the body of the case which will be subsequently tapered.

After exiting the press following the heading, piercing, and tapering, the parts are washed and dried, then fed into a combination headturning and trimming to length machine. This is the pivot point where the Euro and the US processes diverge. In the US process, the headturning is performed before the body anneal, while the Euro process waits until after the body anneal and taper to do the headturning. The US process uses the headturned extractor groove to hold the case during the tapering operation, while the Euro process does not rely upon this.

In addition, the US process uses an “open die” for the heading operations, which results in a flange being formed during the heading. Typically, the flange is a 45 degree angle out from the body of the case, allowing room for the metal to flow so that the cold working will harden the internal areas of the head surrounding the primer pocket.

The Euro process has depended much more on a two blow heading process, so they typically use a “closed die” for the heading operations. Very little or no flange is formed during the heading operations, but rather they depend on a back and forth style of material flow, where the pre-pocket forms some of the primer pocket but also pushes the face of the head up. The following final pocket forms the finished primer pocket and the headstamp.

The origins of the difference in the processes probably relates to the use of “Boxer” style primers in US type ammo, and “Berdan” type primers in Euro ammo. That the Berdan in Berdan primers was a New York native and Boxer was an Englishman only adds to the confusion.

Most Euro processed ammo has the flash hole drilled, rather than pierced. This originally was due to the very small diameter of the Berdan type flash holes, which could not be reliably pierced due to the ratio of the hole diameter to web thickness. Skinny punch, thick metal, not good. Only the later machinery, tooled to produce the Boxer type primer pockets, can use the piercing method described above.

Now, the Euro cases are exiting the tapering operation without a headturn and without a final trim. The next step, following a wash operation, is the headturning and trimming, which is performed in a dedicated lathe. As the component is now tapered, it can be pushed into a fixed conical collet, and turned. Cutters for the headturn approach straight in to form the extractor groove and head form, while a single point cutter is introduced at the mouth end to trim the case to length. Many of the mouth trim cutters operate on two axes, so they can cut the case to length, then chamfer the inside of the case mouth to make inserting the bullet easier.

Following the headturn and trim, the cases are washed and a mouth and neck anneal is performed. Euro process cases are often washed after these steps, but it is not uncommon to see NATO homologated countries leave the anneal corona in place like the US military ammo.

All of the above commentary has been related primarily to the manufacture of rimless, necked rifle cases, with an emphasis on the military types, and all relating to brass. I have no experience, but I have been told the steel case manufacturing process is very similar, but a bit more strenuous. Additionally, steel cases must be either treated after manufacture, using lacquer, phosphate coating, copper washing, or some other sealant, or the case cups must be made from “clad steel”. Clad steel is steel that has a brass layer plated to both sides prior to the cupping operation. The cladding operation can be anything from explosively clad brass to electrochemical plating. The brass cladding acts both as a seal to prevent moisture reaching the steel, and as a sacrificial element to minimize corrosion.

Pistol case manufacturing is generally much simpler, but of similar process. Making rimmed cases of any type (.38 Special for example) is a bit more difficult as the case head must be formed out much further than a rimless type head, but it is easily done on available surplus machinery.

If you have any comments, corrections, or questions, let me know.

Edit: The link to Demsey MFG has a couple of good animations on punch operation and the draw process.  Also, cartridge brass is 70% copper and 30% zinc.