January 04, 2011
How the incredible cartridge case is made is quite a story.
The brass cup is the first step in producing a finished cartridge case. Brass cups in the thousands await processing into cartridge cases.
l"ll admit it. I'm a scrounger and a brass hog. I'm the kind of guy who has a stockpile of once-fired .35 Remington brass I've been accumulating for years but have never, ever owned a gun chambered for the .35 Remington. I'm the guy who'll pick up discarded brass at the local range without even thinking about it and later wonder how the heck I ended up with .380 ACP cases in my pocket when I was shooting a .45 ACP. There's just something about a cartridge case that makes me pick it up.
Part of that probably goes back to my introduction into reloading when I was 16 years old. I bought a Lyman Ammunition Maker reloading set in order to keep myself in ammo for an old 1903A3 Springfield. I can confidently claim that I produced some of the worst ammunition ever fired using this "nutcracker" hand tool. That had absolutely nothing to do with the equipment I used. It was purely a matter of my skill--or lack of it. Thank goodness I never realized at the time just how bad my ammo was because my shooting skills weren't much better than my ammo.
Even now in my 60s I still shoot, reload, and pick up brass. Not too long ago, during a reloading session down in my shop, I was looking at some .223 cases. They'd been reloaded a number of times and were ready to be discarded. In several instances, the necks had cracks where they were beginning to separate from the case body. As I looked at those cases, it got me to thinking. I had been reloading for close to 50 years, but I knew darn little about how cartridge cases are made. That, I decided, was going to change.
Fortunately, living in central Missouri, I'm not all that far from the town of Sedalia, which happens to be the home of Starline Brass. Starline is well known as one of the premier producers of cartridge cases for both commercial and private use. All it took was a phone call, and I was set for a tour.
Robert Hayden Jr., the vice president and general manager, gave me a tour and also answered a multitude of questions, helping me develop a better understanding of the deceptively simple brass cartridge case and how it's made. It's quite a story.
The heat-treating furnace.
Making Brass The Starline Way
Cartridge cases can be made of a variety of different metals and other materials. For example, they can be--and sometimes are--made of aluminum alloy or steel or even plastic. They don't have to be made of brass. However, brass has unique qualities that make it the best material in most situations for commercial cartridge cases. It's malleable in that it can be easily formed or shaped. It can also be readily heat-treated to control hardness. It's relatively inexpensive and available.
Brass also lends itself to reuse, which is a major factor for guys like us who reload.
The brass used in cartridge cases is an alloy made up of copper and zinc. Copper makes up about 70 percent of the alloy, and zinc constitutes the remaining 30 percent; this is pretty standard throughout the ammunition industry. Just to put this in perspective, most jacketed bullets are made with a jacket of gilding metal, which is generally about 95 percent copper and 5 percent zinc. Zinc is used because it adds hardness to the alloy. Copper alone would be far too soft to withstand either normal handling or the extreme pressures inherent in modern cartridges.
After being pulled from the heat-treating furnace, the basket of cartridge cases is lowered into the quench tank to cool the heated and annealed cases.
The process of making a cartridge case begins at an automatic punch press where dies are used to punch small brass cups from sheets of brass alloy. The size and specific dimensions of the brass cups will vary depending upon the cartridge case. A .460 Smith & Wesson Magnum cartridge case takes a much bigger cup than a .30 Luger case. Starline uses 10 different size cups. Using the optimal size cup allows for minimal waste or excess metal that'll have to be removed during the manufacturing process.
The brass cups are further formed in vertical presses using precision-ground dies anywhere from two to four times. The process is called a vertical draw. Even though these presses can exert tons of pressure, there is a limit to how much the metal cup can or should be shaped at any one step or draw. If you exceed that limit, you'll damage your forming dies and will definitely have inconsistency in the wall thickness of your cases.
As the brass goes through the drawing or shaping process, it changes and becomes harder. This is called work hardening. Consequently, the cases have to be annealed or softened between each draw to maintain a consistent and appropriate hardness. Annealing is done by heating the cases in a furnace to a temperature of approximately 1,100 degrees and then quenching in a water bath.
The basic steps in making a cartridge case are shown here.
Why is annealing so important? Alloy consistency and hardness are directly related to uniform case wall thickness. The more uniform and controlled the hardness throughout the manufacturing process, the more consistent the case wall thickness. It also has a major impact on the strength, durability, and life of the cartridge case. The number of times you anneal your cases is one of those critical areas where manufacturers have different standards. Makers of top-quality cases, such as Starline, anneal multiple times and don't even consider cutting back on these critical steps even though it would obviously save time and money.
After drawing, the cases are cleaned in large tumblers that look like concrete mixers. Cleanliness of the case is important in manufacturing because it prevents damage to the forming dies an
d ensures that the case is free of scratches and other blemishes.
The cases are then trimmed in semiautomatic lathes. Some manufacturers trim their cases by pinching or shearing the mouth of the case. Use of a lathe with a precision-ground cutter ensures that the case mouth is always smooth and even. It also gives the manufacturer greater control over the length of the case.
Trimming is followed by another cleaning, and then the cases are headed. Heading is the process in which the case head is formed. Basically, the head is shaped by swaging or striking the closed end of the cartridge case with a heavy punch. During this process the primer pocket is also formed, and the headstamp or identifying information is impressed into the rear face of the cartridge case. Heading also serves to impart the proper hardness to this critical area of the cartridge case through work hardening.
The punches used to form the primer pocket are very important. Small, very subtle variations in angle, diameter, and overall shape of these punches can--and will--make a big difference in the uniformity of the diameter, depth, and radius of the primer pocket.
An automatic lathe is used to trim the case, ensuring an even, smooth case mouth.
Once the primer pocket has been formed, the case head is then turned. During turning, a lathe is used to cut the rim and the extractor groove. It's during this step while cutting the extractor groove that the thickness of the rim is set.
After inspection the cases are vented. Venting is the set where the flash hole is punched between the primer pocket and the inside of the cartridge case. Starline uses some very ingeniously designed tooling to ensure a burr-free and properly centered flash hole. In addition, the company uses a laser to check each and every case to make sure the flash hole is properly centered and fully formed.
The case is then trimmed to the finished length on one of many automatic lathes. As before, this machine ensures that the case mouth is perfectly square and has a nice, smooth finish.
If the case is a bottleneck design, such as the .308 or .30-06, the case again goes through heat-treating, and the neck is then formed in swaging dies. After that, the cases are cleaned, polished, and given a final inspection.
After heading, the primer pocket is fully formed, but the flash hole has yet to be made.
In one sense the actual process is fairly straightforward, easy to follow, and simple to understand. As Hayden pointed out, anyone with the proper tooling can make a cartridge case. The trick is to make a good one. Not all cartridge cases are the same, and that applies to manufacturers as well.
When I first sat down with Hayden, I showed him some unfired cartridge cases from another maker. Several of these brand-new cases had vertical cracks. It didn't take him more than a moment after examining them to point out that they were too hard and had not been properly heat-treated. In addition, the quality control at this other company had obviously been pretty minimal since these cracked cases had been packaged, shipped out, and eventually received by a customer--me.
Good manufacturing is not just tooling or machines. It involves attention to the smallest detail and the rigorous adherence to a very high standard of performance. Good enough just won't cut it if you want to produce a superior product. You have to have a real commitment, and this has to be shared by everyone from the head guy in the corner office on down to the fellows running the machines. Everybody in the shop has to be on the same page.
A laser in this machine is used to check the location and uniformity of the flash hole.
One of the things I noticed as I watched the various stages of cartridge case production was the incredible number of times men and women checked the cartridge cases with micrometers and various gauges. At each individual stage, there were numerous quality-control checks. In addition, I saw other folks periodically checking the micrometers and gauges. That redundancy is essential if you want to make a cartridge case that's better than just "good enough."
Some companies use machines that you can almost feed brass into one end and they spit out completed cases at the other end. That can be fine for saving time and getting maximum production, but it doesn't necessarily mean that you'll get the best quality case. If something goes wrong somewhere inside that machine, will you be able to catch it? Maybe you will and maybe you won't.
The folks at Starline deal with that sort of potential problem in a number of ways. Each machine operator is constantly checking the cases as they come off his or her machine. The machine itself is also being constantly monitored to ensure that it hasn't slipped out of adjustment or that the tooling hasn't worn or developed a flaw.
As the cases are moved about from one machine to another, they're kept in batches in what are called containment trays. These are constantly checked, and if a flaw is found in even one case, the entire tray is scrapped. If there's a problem, they find it and quickly isolate it.
Even with all the precision gauges and measuring tools, skilled, experienced people visually check each and every case throughout the manufacturing process.
Another feature I found to be interesting--and reassuring as a consumer--is the documentation that accompanies each batch of cartridge cases. At each step in the overall procedure, the person running the machine or in charge of a particular process, such as heat-treating, had to personally sign and date this work record. If there's a problem or if a flaw is found in the cartridge cases, the folks at Starline could determine exactly when it happened and who was responsible. This means they can correct problems, and also by making everyone accountable, they avoid problems in the first place.
At any one time, seven or eight different calibers or cartridge cases are in production at Starl
ine. And it can take anywhere from two to 20 hours to change and set up the machines when switching from one caliber to another. Currently, Starline produces over 92 different calibers, and more will be added as time goes along. Starline, as one of the smaller cartridge case manufacturers, is in the unique position of being very flexible and quick to respond to consumer demand for new cartridge cases.
Starline has been especially active in providing many of the newer large-caliber handgun cartridge cases, such as the .400 CorBon, .454 Casull, .460 Smith & Wesson Magnum, .475 Linebaugh, and .500 Smith & Wesson Magnum. Starline has also been a major supplier--often the only supplier--of cartridge cases for many of the older blackpowder cartridge cases like .45-90 and .50-90.
More often than not, the "big boys" in the industry just can't tool up and supply these "niche" cartridges. They operate in terms of volume. If they can't sell millions of rounds, they just can't do it economically. Years ago I was working with a company that needed to have a special cartridge made up. Every U.S. manufacturer we talked with at the time required a production run of at least one million rounds! That is a lot of ammo.
A small outfit like Starline can be much more flexible. But even here they have to look at the potential demand. I might have a great idea with my wildcat .432 Super Whiz Bang cartridge, but will anyone else care or want it? Probably not. To tool up for a new cartridge case, Starline looks for a minimum production run of between 100,000 and 200,000 cases. If the demand is less than that, they simply can't justify the production costs. They'll lose money on the project, and in today's business climate, you just can't do that. So I guess my .432 Super Whiz Bang will just have to wait.
If you want to produce premium cartridge cases, you have to keep records of what has been done and, most importantly, who did it.
I left Starline with a great appreciation of what it takes to make a good cartridge case. I hadn't realized just how many individual steps, machines, and people were involved in the manufacturing of the deceptively simple cartridge case. I also had not fully appreciated the more subtle aspects of the manufacturing process. The way in which a manufacturer can use and control the natural tendency of brass to work harden to obtain a specific hardness to certain parts of the case was absolutely amazing. It was fascinating to see how with just very slight modifications to tooling the flash hole or primer pocket could be altered.
I'll probably keep scroungin' brass whenever I go to the range. I'm just too old and set in my ways to change. However, I've definitely learned to appreciate the difference between the typical piece of mass-produced brass I pick up and a premium custom cartridge case. It's like the difference between the family sedan and a high-performance sports car. Both will get you from point A to point B, but one is a lot more enjoyable to use and will give you that extra bit of performance when you need it. Maybe that "free" range brass is not all that much of a bargain.