Form: Man10G107 Rev. –C-
02-06-2012
7
IV. Annealing Info and Why Annealing Helps
Please take a minute and read why
BENCH-SOURCE
made the decision to provide our
Annealing Machine to shooters like you. After all we have been shooting for longer than we will
be truthful about!
First off, the term annealing is applied to many different types of materials throughout many
industries in the world. The term is used to indicate that a material such as steel, brass, copper,
plastic and some rubber needs to be softer. The purpose for this softening varies as much as
the types of materials that can be annealed.
For example, when we anneal any type of steel in general, it is usually to improve machinability,
to modify features or add features that can not be done in a heat treated state. Sometimes it is
used to make the properties of the material last longer or more stable and sometimes to
accelerate wear to minimize failure of mating parts.
When steel is annealed it is heated to perhaps 1800° F or more and allowed to slowly cool in
still air. This will bring the material to its most malleable or soft state. After annealing it will bend
or deflect with less resistance and usually without breaking or splitting.
When we anneal cartridge cases, we are also softening the material in an attempt to lower the
hardness. While most steel will harden by working it excessively, all brass, bronze, copper and
other non-ferrous materials are easily work hardened.
Most cartridge cases are made from material known as Cartridge Brass. It is an alloy of 70%
Copper and 30% Zinc. Alloys of the brass will vary slightly from one manufacturer to another
but 70/30 is the base line. The reason this material is chosen is because it forms well, is less
expensive than other brass or bronze with a higher copper content and is well suited to being
hard in one area such as the case head area, while remaining fairly soft in areas such as the
neck and shoulder. As you may imagine or by referencing your reloading manuals, flame
temperatures in modern cartridges using smokeless powders are usually in excess of 5000
°F
.
If the cartridge case didn’t expand and seal in our chambers properly on firing, many of us
would not be here today! This brings us to the explanation as to why we need to anneal.
Many people reference the fact that you heat steel to make it harder. While this is true, it is not
heated to the same temperatures as to anneal the material. The effect of heating both of these
materials is essentially the same. When your cartridge cases are heated to 650°-700°F they are
annealed, but not to a dead soft state. The intent is to lessen stresses from sizing & re-sizing
and to soften the brass in the desired areas to minimize work hardening. When you anneal you
are transforming the grain structure from rather small and tightly constrained into an elongated
and more loosely constrained state.
By returning your brass to this condition, you will give it a longer life by eliminating
neck/shoulder splits while realizing better accuracy from uniform neck tension on your reloaded
cartridges. Of course other areas such as the primer pockets, case stretch and head condition
will determine how long your brass will last in a given caliber and type of cartridge.
CAUTION:
Based on the information above, we would like to caution you, the reloader, that
special attention to important items such as recording the number of firings and