Want more bang for your buck at the reloading bench? Learn the fine art of annealing brass.
What Is Annealing And Why Is It Important For Reloaders:
- It's the process of heating and cooling a case so the brass regains its malleability.
- If brass isn't annealed, it will eventually become brittle and break.
- The process extends the life of your cases and saves you money in the long run.
- It also tends to improve the accuracy of some rifles.
You might have noticed it on the neck and shoulder of your rifle cases—a rainbow-like coloration on the brass case. What you’re seeing is the result of a process called “annealing,” which is a means of keeping the brass soft. Simply put: The brass is heated to a temperature between 500 and 800 degrees (Fahrenheit) and then quenched to cool rapidly.
The Chosen Metal
Brass was chosen as a material for our cartridge cases for its malleability, strength and rigidity. It’s durable enough to withstand the rigors of life (copper was tried, but it proved to be too soft—as the stuck cases from the battle at the Little Big Horn showed), yet it is pliable enough to be easily formed and reshaped.
Brass, unlike steel, becomes softer when heated and immediately quenched. Again, in the opposite manner of steel, when brass is repeatedly worked, it will become brittle and crack.
In a perfect world, our cartridge case would be formed to SAAMI specification and, upon firing, the shoulder and neck portion would expand to become a perfect mirror of the chamber, fully sealing the gases in the chamber.
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Sometimes, you might find a sooty residue on the neck of your fired cases; this is from brass that hasn’t fully expanded to the chamber diameter. If you see this, odds are the brass isn’t expanding properly. Annealing can solve the problem.
Annealing for the Reloader
Lapua, Norma and Hornady brass often shows the effects of annealing at the factory (that aforementioned hazy rainbow look). And these brands will often show that they can be fired and resized more times than some of the other brands.
For a reloader, the ability to anneal your cases might not be such a bad thing. If you’re forming your own cases—for a wildcat design or making brass cases for an obscure or obsolete cartridge—annealing will help in the forming process and will also help preserve the cases once finished.
For example, I frequently form brass cases for my .318 Westley Richards from .30-’06 Springfield brass, and the process works the material considerably. For this particular operation, the case must be trimmed from 2.494 inches down to 2.370 inches and then run through the resizing die, which relocates the shoulder and opens the case mouth and neck from .308 inch up to .330 inch. That doesn’t sound like a whole lot, but to the grain structure of a brass case, it means a diminished life expectancy, at least in the configuration we need.
The cost of brass cases for big-bore rifles or for the rare and unusual cartridges can be huge and result in a serious investment. Some of the big Weatherby cartridges, such as the .378 and .460 Magnums, along with the big Nitro Express and other safari cartridges, can cost between $3 and $8 per case. As a reloader, I do everything to keep those expensive cases around as long as possible, including annealing the brass.
The Annealing Process
So, how can the reloader anneal their own cases?
The principal idea is to heat the neck and shoulder of the case—but certainly not the body and base. A common method that’s inexpensive yet effective uses a blow torch to heat the cases just enough to get a dull-red glow and then place the cartridges into water. Do not overheat the case, because you’ll ruin it. Although the annealing results from this method might not come out as uniformly as others, it’s certainly better than nothing.
Brass Annealing Machine
I’ve found a cool (albeit expensive) unit that handles annealing very well. The folks at Annealing Made Perfect (New Zealand; AMPannealing.com) make a machine that gives all sorts of flexibility and will handle cartridges from the .17 Hornet all the way up to the .50 BMG. Described as “the world’s first and only smart annealer,” the machine is easy to use and makes it simple to customize your brass cases.
Using induction to generate heat, AMP makes a series of pilots, which work as spacers, to place the case mouth, neck and shoulder at the proper height within the machine. Each family of cartridges—say, the .308 Winchester, .260 Remington and .338 Federal as one family and the .30-’06 Springfield, .270 Winchester and .280 Remington as another—will use a common pilot. Simply thread the pilot into the top of the machine and, using a common shell holder that inserts into a small unit designed to keep your fingers cool, the unit can be set to a specific program time to give the proper amount of heat.
You will find a chart of varying calibers on the AMP website, and within the caliber, varying brands of brass, along with the appropriate program time. Set the front display to the proper program time and hit the start button. Within seconds, you’ve got as good an annealing as you could ask for. I put the machine through its paces and found it would crank out about 300 cases per hour.
The AMP machine also is compatible with the AZTEC program, which will have the machine test (and ultimately destroy) one of your cases to determine the properties of the case, as well as how long a runtime your particular case will need.
This device should have all sorts of appeal to wildcatters who create their own unique designs. With a street price of around $1,400, this is a major investment for a single reloader. However, for a shooting club or rifle range, a group of shooters could split the cost, and it would make sense.
Is annealing a necessity in order to reload ammunition? No, but it most certainly extends case life—and I’ve also found it to improve accuracy in many of my rifles.
If you find yourself shooting enough to wear out cases, maybe it’s time for you to add annealing to your reloading routine.
The article originally appeared in the June 2019 issue of Gun Digest the Magazine.