(This blog is mostly about journaling my own adventures in learning. As I love my hobby with a passion, so do I love the learning process that comes with it. If someone else can profit in their enjoyment by my scribbling, then that’s icing on the cake. That’s what this article is about… a description of some of what I have learned regarding annealing brass case necks. As always, click on any images to enlarge them.)
So… what is annealing, and why bother with it?
Different metals react in different ways to stress and pressure. Steel, when heated to the correct temperature and cooled quickly (quenching) will grow harder. This is called heat treating. Reheating it to a certain temperature and letting it cool slowly will make it less brittle, and is called tempering. Aluminum does something different, as does lead, and so with brass.
Brass does not harden with temperature, but with ‘work’. As it is stretched, pressed, and sized it becomes harder, and more brittle. Simple age has a similar effect on brass. Taken too far in the process, brass will crack and fail. That’s what happens to cartridge case necks as they are reloaded multiple times. It’s especially prevalent with high power bottle neck rifle cases, and even more so with those getting heavily resized with each loading.
One of the features of brass is that it can be ‘annealed’, or softened with heat. Heated to a certain temperature, it becomes softer and less prone to cracking. The effects of many reloadings and firings can be negated with a single annealing process, allowing the cases to be reused far beyond their normal life span.
Annealing is also a pet technique of the long range precision bench rest shooters. These folks cringe or celebrate over a quarter inch group variation at five hundred yards. To them, annealing the case necks is a standard part of the hand loading process, as they aim at ‘precision nirvana’.
My reason for wishing to anneal case necks…. is that I’m too cheap to buy new brass. The Grand Old Turk I shoot in the rifle matches has a set of hand loads worked up on cases made in 1944. They were used when I got them, and I’ve since loaded them eight or ten times. They are starting to show their age! The last match I fired, I lost a case due to a cracked neck… and that means they are all ready to do the same. A new matched set of brass would cost me mo..mo..mo..money, and that is not acceptable if I can avoid it. Finding once fired and reloadable 8x57mm brass on the ground at the range… well… I won’t hold my breath waiting for that to happen.
Doing a Google search on ‘Annealing case necks’ will return thousands of hits, and at least a few of them will be scholarly works on the metallurgy of the process, and how to do it correctly. It’s not a mystery process, suited to hooded monks working in mystical caves. The only discussion that matters is in the process itself, with the real question being this: ‘How can it be done safely, uniformly, repeatedly, and for a reasonable price?’
There’s a dozen ways to do it, and many of them are workable. Some are downright dangerous, and one or two are impressively high tech (and expensive). This article is about the method I worked out for myself, being a compromise to reach my simple goal. I’ve borrowed points and ideas from several sources, putting them together into an easy process that appears effective, safe, and inexpensive.
The temperatures used are critical, for several reasons. Foremost among them is safety, as the lower body and base of the cartridge case must never be annealed and soft. If it’s heated above 480 degrees or so, the grain structure of the metal will change and the case may not be able to contain the pressure of firing (think face full of flaming debris). On the other hand, the case neck must be heated to about 750 degrees for some seconds for the annealing process to take place. Doing one without doing the other is the real trick.
The next problem is actually judging the temperature correctly. Some folks swear by working in a darkened room and judging temperature by the color change of the case. In other words, they watch it turn dull red under the flame, and then quench to stop the heat spreading. The problem with this method is one of judgment and timing. The line between ‘dull red’ and ‘turning orange’ is only a few degrees and a few moments in time. Over-annealing the case will make it too soft, and ruin it.
I found and use a ‘Tempilstik’ to judge temperature. This is a chalky crayon type of marker used by welders and metal workers. Rubbed on the metal to leave a mark, the material will melt at a relatively exact temperature. It costs about $11.00 at most welding supply stores, and is usually in stock. They come in varying temperature ratings, and I chose 650 degrees for this use.
I found it’s best to work with dirty, as-fired cases. Brass cases freshly cleaned are very hard to mark with the chalky Tempilstik, and the cases need to be cleaned and sized after annealing in any case.
Using the temperature sensitive marker, draw a line of the material around each case about ¼” below the shoulder. During heat treating the neck, the heat will soak through the brass to the body, melting the marker when it reaches 650 degrees at that spot. The neck will be hotter, and should be in the correct range for annealing. It takes six to eight seconds for the heat to soak that far, and that’s long enough for the annealing process to happen. I found that even a faint line of Tempilstik is visible while the case is spinning, and not much is required. The state change from solid to liquid of the indicator marker is readily visible under good lighting.
The cases are slowly spun in the flame using a battery powered drill/driver with a low speed setting. As a case holder, I used a 1/4” drive shallow 1/2” socket, with a 1/4” bolt inserted through the square drive hole and a nut tightened in place. The shaft of the short bolt that protrudes can be chucked into the drill/driver snugly. Spinning the case within the flame makes for an even annealing process, and is the biggest reason I opted away from the ‘pan of water’ method.
The process works like this:
Have a propane torch standing on the bench. It works best if the short and squat cylinder is used, giving the torch a wide base to stand on. Have the torch running full blast, with the flame pointed away from you (and NOT at flammable objects!).
Have a small pan of water on the bench just in front of the torch, placed so the case can be tipped into it from the holder once proper temperature is reached.
Have the case holder chucked in the drill/driver, and the tool set on its low speed ‘driver’ setting. Begin spinning the case before it’s moved into the flame.
With the case spinning, move the neck into the flame until it’s fully enveloped. Make sure the flame is pointed from the base of the case to the mouth, and the flame washes away from the body of the case. Do not have the flame wash over the Tempilstik marking as it will melt at once, no matter the actual temperature of the brass case.
With the case spinning, and the neck enveloped in the propane torch flame, watch the temperature indicating marker. Once it melts, tip the holder forward and dump the case into the water.
That’s it. The case is now ready to be sized, polished, trimmed, and reloaded.
It’s advisable to practice the process on scrap cases until the timing and rhythm is learned. I went through half a dozen junk 30-06 cases as I learned how to hold the case in relation to the flame and for how long. Once this is worked out, repeatability is good and a large batch of cases can be done quite quickly. It takes longer to scratch on the marker than the actual annealing process takes.
Annealing case necks is not something that needs to be done often, unless extreme precision is the desired outcome. For rifle cases that are to be loaded more than a few times, it’s a good technique to use. If the shooter is forming cases through a multi-step die process, annealing the necks is a must-do step. For ancient brass, unusual calibers, or perhaps for those of us just too cheap to buy new cases…. annealing can save the day.