Annealing brass is an increasingly popular process amongst shooting aficionados, as it allows you to reload and reuse your old cartridges multiple times. The term brass annealing refers to the softening and revitalization of brass through the use of heat to refresh its structure back to its original state.
Annealing refers to heat treatment that alters brass’s molecular properties and restores its ductility. Ductility simply means the ability of a given material to change shapes without losing any strength.
Let’s take an in-depth look at the brass annealing process and how you can use the process with your old brass cartridges to enhance their lifespan.
The Annealing Process: An In-Depth Look
Annealing involves heat-treating brass to a specific temperature for a specific duration and then cooling it slowly. If done correctly this will lead to an increase in ductility and a reduction in hardness.
The reason you want to reduce hardness is because increased hardness is associated with increased brittleness. In other words, the harder brass or other metals for that matter get, the easier they’ll break and crack when shaped.
Additionally, annealing will help increase corrosion resistance by stopping internal stresses from accumulating, leading to cracks forming over time.
As you may or may not be aware, brass is a metal alloy made from a combination of zinc and copper. When annealing, you first want to determine the ideal temperature based on the specific alloy. This will generally fall somewhere between 600 and 800°F.
Once the right temperature has been chosen, the brass is then placed inside a furnace or oven and heated until it reaches that temperature. Then, the metal is allowed to air cool or cooled using a liquid like water or certain oils. Keep in mind that unlike iron, which requires a very specific cooling environment, brass can be air-cooled and will still retain its strength.
After annealing, the metal’s surface can be tested for hardness/softness. If the desired level of softness isn’t achieved, you can always repeat the process until you attain the level of pliability your’e looking for.
How to Anneal Brass Cartridges
When it comes to brass cartridges, the annealing process is often completed using a handheld blowtorch rather than an oven. The reason for this is that the only section of the cartridge that generally requires annealing is the shoulder and neck of the casing. The long, uniform casing body generally does not require annealing, as it doesn’t undergo the same level of stress as the neck and shoulder do during firing.
To anneal brass casings, use a blowtorch to heat the neck and shoulder of the casing until it reaches your desired temperature. You can submerge the lower part of the casing in water to prevent it from heating up during this process.
Be sure to heat the entire circumference of the casing evenly by applying the flame evenly to the entire area around the casing to heat it evenly. The color coming off of the
Then, allow it to air cool at room temperature.
If the process has been done correctly, then you should notice a distinctive metallic rainbow pattern on the casing after the casing has had the opportunity to dry completely.
Why Anneal Brass?
So, why does brass need to be annealed in the first place?
We went over a few of the reasons to anneal your brass casings, but there are numerous additional benefits worth mentioning.
Brass – and brass casings in particular – undergo a tremendous amount of stress through repeated firing and reloading. What this does is cause ‘work hardening’ of the metal, which means it gets harder and harder every time it’s fired. Eventually, this can even cause the casing to split inside the chamber – leading to a serious malfunction.
This of a brass casing like a thin piece of metal that is stretched back and forth over and over. At a certain point, the piece of metal is going to break rather than bend. Annealing essentially reverses this process and restores the metal’s strength to new.
The regular annealing of brass will greatly extend the longevity of your casings, as in addition to the above-mentioned benefits, you’ll remove any accumulated micro-fractures and cracks that could lead to dangerous malfunctions.
The frequency of annealing depends on your preference, but it’s generally recommended to anneal casings every 3 to 4 reloads. Some people anneal every time they reload, although this is likely overkill in most cases.
As long as you are annealing and reloading correctly – it is commonly suggested that there is no such thing as annealing casings too many times.
Things to Watch Out For
Annealing brass – whether cartridges or otherwise – is not all that difficult of a process, but it can be done incorrectly, leading to over-annealed or under-annealed brass that won’t perform as expected.
Over-annealing happens when you apply too much heat to the brass – and will cause it to be too soft and potentially unusable as a brass casing. When using a blowtorch to anneal, you’ll know you’ve gone too far when you notice the flame coming off the casing change to an orangish color – indicating you’ve started to burn off part of the alloy (typically zinc or tin).
When this happens, it indicates you’ve gone too far, and casings won’t be useable anymore.
Another indication that you’ve over-annealed is the casing will start to glow. Once again, this means you’ve over-annealed and will need to discard the casings to prevent a potential malfunction.
Under-annealing is less of a serious issue than over-annealing, as you can always repeat the process over again. You’ll know you’ve under-annealed when the metal remains hard and brittle.
All of this can seem a bit tricky – but there is a method to ensure you’re annealing your casings correctly. Applying heat-sensitive paint like Tempilaq to your casing will let you know when you’ve reached the precise right temperature – as it begins to melt when it reaches a specific temperature. If you’re going to use something like Tempilag, then be sure you get the right one to match your required annealing temperature, as different brass anneals at different temperature ranges.
Annealing Casing Body
One thing you want to be sure to avoid is annealing the casing body during the heating process. When using a blowtorch this is easier said than done, as it can be difficult to avoid heating the casing body at the same time.
Annealing the casing body is a bad idea as it will cause it to become softer and more pliable. In the context of casings, this has the potential to lead to the head separating from the body.
To avoid this, keeping the casing body submerged in water while the head and shoulder stay above is recommended in most cases.