Annealing Case Necks…. A Simple And Safe Method
What’s what is annealing, and why bother with it
Different metals react in alternative ways to stress and pressure. Steel, when heated to the proper temperature and cooled quickly (quenching) will grow harder. This is named heat treating. Reheating it to a certain temperature and letting it cool slowly will make it less brittle, and known as tempering. Aluminum does something different, as does lead, and so with brass.
Brass doesn’t harden with temperature, but with ‘work’. As it’s stretched, pressed, and sized it becomes harder, and more brittle. Simple age has an analogous effect on brass. Taken too far in the method, 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 much more so with those getting heavily resized with each loading.
One of many features of brass is that it can be ‘annealed’, or softened with heat. Heated to a certain temperature, it becomes softer and fewer susceptible to cracking. The results of many reloadings and firings could 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 typical 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 purchase 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 once i got them, and I’ve since loaded them eight or ten times. They are starting to indicate their age! The last match I fired, I lost a case attributable to a cracked neck… and which means they’re all able to do the identical. A new matched set of brass would cost me mo..mo..mo..money, and that’s 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 the least a few of them will be scholarly works on the metallurgy of the method, 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 method itself, with the real question being this: ‘How can or not it’s 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 text is about the method I worked out for myself, being a compromise to achieve my simple goal. I’ve borrowed points and ideas from several sources, putting them together into a simple 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 capable of contain the pressure of firing (think face stuffed with flaming debris). Alternatively, the case neck must be heated to about 750 degrees for some seconds for the annealing process to happen. Doing one without doing the opposite is the true trick.
The following problem is definitely 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, after which quench to stop the heat spreading. The problem with this method is one in every of judgment and timing. The best virgin hair suppliers road 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 evaluate temperature. This can be a chalky crayon type of marker utilized by welders and metal workers. Rubbed on the metal to leave a mark, the fabric will melt at a comparatively 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 have to be best virgin hair suppliers cleaned and sized after annealing in any case.
Using the temperature sensitive marker, draw a line of the fabric 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 must 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 may be chucked into the drill/driver snugly. Spinning the case within the flame makes for an even annealing process, and is the largest reason I opted away from the ‘pan of water’ method.
The method works like this:
Have a propane torch standing on the bench. It really works best if the short and squat cylinder is used, giving the torch a wide base to face on. Have the torch running full blast, with the flame pointed away from you (and never 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. Be certain that the flame is pointed from the bottom of the case to the mouth, and the flame washes away from the body of the case. Shouldn’t have the flame wash over the Tempilstik marking as it is going to melt at once, irrespective of 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 able 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 carry the case in relation to the flame and for a way long. Once that is worked out, repeatability is nice and a big batch of cases might be done quite quickly. It takes longer to scratch on the marker than the actual annealing process takes.
Annealing case necks isn’t 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 an excellent 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 purchase new cases….
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