Welcome to our Annealing service page !
What is Induction Annealing?
Induction annealing is the process of softening the necks of
cases, through heating in an electrically contactless manner. This is
achieved through placing the cases within a magnetic field, which
induces eddy currents within the brass. Technically, the lower the
resistivity of the brass, or the higher the intensity of the magnetic
field, the greater are the eddy currents and, consequently, the greater
the heating effect. There is no heating element as such; the only thing
to get hot is the case. The magnetic field is focussed to maximise the
eddy currents and heating in the location where it is specifically
required, i.e. the neck and shoulder.
Click the pic to see our machine in action and how it works !
Annealing is part of the manufacturing process of every rifle
cartridge case. As brass is worked in the drawing and sizing processes
it hardens, and has to be selectively annealed to produce the correct
hardnesses at the different parts of the case.
The case head needs to be very hard, while the brass should get
progressively softer towards the neck. The neck itself should have a
nominal hardness of around 95-120 HV on the Vickers scale. So, how
consistent is factory virgin brass? Without naming brands, we have
tested top quality virgin brass with neck hardness as low as 90 HV, and
others as high as 150 HV. The difference is in the finishing process.
Some brands give a final neck anneal to the brass before packaging. That
puts it in the softer range. Others give a final resize. Those are in
the harder range. The good news is that we have generally found
excellent consistency within each lot of any particular batch we have
tested. It is fair to say there is no "right” neck hardness for factory
brass. What does matter is consistency.
So how quickly do case necks work-harden with reloading? The answer
is: really quickly. Just one pass through a standard resizing die with
an expander ball is usually enough to add 20 HV + to the hardness.
Seating the bullet adds another 5 – 10 HV. Interestingly the actual
shooting of the cartridge has a relatively minor effect. We also found
little difference between regular and "hot” loads, but this is just in
relation to neck hardness. "Hot” loads are harder on brass for other
It is apparent that, depending on the die, after only a few
reloads, the neck hardness can go from Half Hard to Extra Hard, almost
the same hardness as the head. The idea that you only need to anneal
your brass every 5 – 10 reloads just isn’t right. To really benefit from annealing, it must be done every reload.
About Brass Hardness
There are two ways of determining the hardness of brass. One is to
microscopically examine the grain structure. The softer the brass, the
larger the grains will be. Typically, very soft brass will have grains
in the range of .040 - .070 mm. Medium soft will be .020 - .035 mm. Once
the brass is mid-range (approx. 90 – 100 HV on the Vickers scale) the
grains will be .005 - .015 mm. As the brass gets harder and harder, the
difference between grain sizes becomes more difficult to distinguish,
meaning this is not a great technique for the upper end of hardnesses
relating to case necks. Also, the test process destroys the case,
meaning it is impossible to do progressive tests on the same cases.
The second method is called the Vickers test, or for small thin
samples (like cartridges), the micro-Vickers test. This involves
creating microscopic indentations with a diamond anvil, using a known
force. The diagonals of the indents are then measured under a
microscope: the longer the diagonals, the softer the brass. This is a
very accurate method, and by using caliber-specific jigs, the cases can
be reloaded and retested. The Vickers scale of hardness is as follows:
How to use our service ?
Simply call us and book on your cases, we will check we have the correct pilot for your cases then ask you to post us your cases to us, we will anneal them and post them back within a few days we charge 10p per case
de primed cases only
cleaned cases only
letter with return address
Buy your own machine !
We sell the AMP for £1125 each
Each shell holder is £20