The Not-So-Arcane Art of Brass Annealing | Top Rated Supplier of Firearm Reloading Equipment, Supplies, and Tools - Sinclair Intl

The Not-So-Arcane Art of Brass Annealing

A lot of folks hear about annealing brass cartridges cases, and just assume it must be something that’s hard to do. Once you understand what annealing is, why it’s done, and what tools you need to do it, annealing is actually a fairly simple process.

What Is Annealing?

Annealing means heat treating the neck and shoulder of a brass cartridge case to make it softer so it will seal the chamber during firing. Unlike steel, brass gets softer as you heat treat it, not harder. What makes brass cartridges become harder is firing the cases in your gun, and then working them in your reloading dies. Both those operations will cause brass to harden, which leads to splits and cracks in the cases.

Why Do We Anneal Brass?

One reason to anneal your brass is to extend its life, so you can reload it more times. One of the first signs that it’s time to anneal is splitting at the case mouth, or cracks in the neck or shoulders of your brass. Another thing to look out for is if it suddenly takes more pressure, or less pressure, to seat bullets into the cases than it used to. Once symptoms like these appear, many shooters think the brass is no longer usable and discard it. But as long as the primer pockets are still tight, these cartridge cases are still useable - if you anneal them properly.

Another reason to anneal brass cases is if you are reforming them from a larger case to a smaller case, such as in making wildcat cartridges. When you set the shoulder back on the case, the neck walls will thicken from the shoulder’s extra brass, which will harden up as you work it into the new configuration. This area of the worked brass needs to be annealed so that when it is fireformed, it will seal the chamber and properly form out to the new configuration.

No matter why you anneal your cases, the key to proper annealing is to not overheat the cases. When you use a flame to heat the neck and shoulder, make sure that you do not bring the brass to a bright, glowing red color. If the brass reaches a bright, glowing red, you have most likely overheated the case, and it will be unsafe to fire, even if you quickly quench it with water.

How Was Case Annealing Traditionally Done?

Many of us familiar with annealing were taught to fill the brass cases halfway with water, and then place them into a pan of water deep enough for the water level to reach halfway up the outside of the case. The water inside and outside the case acts as a heat sink to protect the base of the case from overheating.

An annealing trick that my father showed me, when I was at the tender age of 10, was to work in a fairly dark area. As I heated the cases, they would start to glow with just enough color that I could just barely see it in the darkened room. Once the case heated up enough for this barely-glowing color to spread evenly around the neck and shoulder, I would tip it over with the torch head so the brass would quench in the water it was standing in. This process left the neck and shoulder of the case softer than the middle and lower portions of the case.

How Is Modern Annealing Different?

Today we have better ways of annealing that are far more consistent than the old-fashioned method that I have just described. One of the best ways is to use the Hornady Annealing System, which we sell as our item number #041220. This kit comes with three different size case holders that will allow you to spin the case while it is in the flame for very uniform heating of the neck and shoulder area.

The Hornady Annealing System also includes a bottle of heat-sensitive paint called Tempilaq. This paint is designed to change color when heated to 475° F (246° C). We usually recommend applying the paint to the inside of the case mouth because the flame will ablate the paint from the outside of the case as it heats. You will be able to see the paint inside the case mouth change color as the brass case rotates, and when this occurs, you will want to let the case fall out of the holder into a pail of cool water to quench. Please keep in mind that you can vary how hot the brass gets by using different Tempilaq formulas that change colors at different temperatures. If you need different Tempilaqs for different temperatures, Brownells sells several versions of it.

There are other types of modern annealing tools, such as ring type annealers that rotate at a set RPM as they move the brass cases through a flame. With these ring-type annealers, the brass will usually be allowed to fall though the bottom of the ring into a container of water at the end of the cycle.

No matter what method you use to anneal your brass, the most important thing to remember is not to overheat the middle and base of the case. Overheating the case makes it unsafe to use.

What Else Do I Need To Know?

After a case has been properly heated and then quenched, it is then ready for the balance of the reloading operations. Here is a quick tech tip for those of you wondering what properly annealed brass should look like when it’s done. Just take a look at a new piece of Lapua brass, if it’s available to you. Lapua always leaves the annealing color on the case so that the reloader can see that the case has been properly annealed. A lot of the other manufacturers will polish this annealing color off to make their brass nice and shiny, but Lapua leaves it on their cases.

As you can see, the annealing process can be quite simple to work with, especially with the proper tools like the Hornady Annealing Kit. The paybacks of extended case life, and the ability to reform cases into different dimensions, more than make up for the initial setup cost of what I consider to be an important tool for precision reloading.

As always, if you have any additional questions, please do not hesitate to call any of us on the Tech Staff here at Sinclair.


Bob Blaine
Sinclair Reloading Technician
NRA Certified Reloading Instructor & Range Safety Officer