Lead Hardness Testing Kit
Shooters of cast lead bullets in rifles
and handguns are often bedeviled by problems associated with fit and hardness: Fit as in
the relationship between bullet diameter and barrel groove or chamber throat diameter;
hardness as in the relationship between bullet hardness and the pressure developed by a
given load. In addressing problems associated with fit, one usually needs a Cerrosafe cast
or lead slug of chamber and barrel dimensions and a micrometer.
In dealing with hardness, empirical
evidence will sometimes suffice, but it is usually better to identify actual bullet
hardness and attempt to adjust pressure accordingly or, in some cases, to identify the
pressure level and adjust the bullet hardness. This is so because, assuming proper fit to
begin with, there is a quantifiable relationship between bullet hardness and the pressure
at which the bullet will perform at its best.
To begin on this journey, we attempt to
ascertain bullet hardness in terms of its Brinell hardness number (BHN). The technique was
developed by Swedish metallurgist Johan Brinell and involves pushing a steel ball into the
metal being tested and measuring the indentation. The load applied to the ball is divided
by the surface area of the indentation to give the BHN. A tool to accomplish this has been
recently introduced by Lee Precision of Hartford, Wisconsin, called the Lee Lead Hardness
The Lee tool is not the first such to
be made available to handloaders for measuring bullet hardness, joining, as it does, tools
from Redding/SAECO and Lead Bullet Technology (LBT). The SAECO unit gives repeatable,
comparative readings on a 1-to-10 scale but does not convert them to BHNs. The LBT tool
does provide a direct BHN reading but had been off the market for some time. Im told
it is now available again. The Lee tool is available and, through the use of a chart,
provides BHNs. It is rugged and, as befits the Lee Precision legacy, is inexpensively
When I first became aware of the Lee
tool, I jumped at the chance to test one, in part because I was interested and because I
already had the LBT tool and wanted to see how closely the measurements from the two tools
The Lee kit arrived in the
companys familiar red rectangular box. In it were a Calibrated Hardened Steel Ball
Indenter, a V-Block Cradle, a 20-Power Optical Microscope and instructions. The indenter
is shaped much like a reloading die, has 7/8x14 threads and screws into your reloading
press. Inside is a spring-loaded plunger with a steel ball on the lower end. The upper end
is a rod that will protrude through a hole in the top of the body when enough pressure is
applied from below. The V-block cradle is much like a shellholder and fits into the press
ram. A V slot is cut across the top of the cradle to hold the bullet to be measured.
In use, the indenter and V block are
installed. The bullet to be tested is secured in a vise or held by pliers or something
similar and a flat is filed on one side of the bullet. The bullet is placed in the V
block, flat up. The press ram is raised until the indenter ball is resting against the
bullet flat. The ram is then raised against the pressure of the spring until the rod
appears even with the top of the tool body. Pressure is maintained for a minimum of 30
seconds and released. The bullet and V block are then removed, and the diameter of the
impression in the bullet is measured using the micrometer.
The micrometer is an aluminum tube
about 4 7/8 inches long and 7/16 inch in diameter. Inside is a four lens, 20x magnifier.
On one surface are etched a series of 50 marks, or divisions, that run from .00 to .10,
each division equaling .002 inch. By placing the microscope against the bullet and
aligning the left or zero mark with the left edge of the impression, the diameter of the
impression can be read on the right, in thousandths of an inch. From the chart included in
the instructions, the BHN can be ascertained.
As I started to use the kit, I
discovered there was a significant learning curve. I also experienced three difficulties
that had to be overcome. Making the impression in the bullet and holding the pressure for
the prescribed time was easy, although I had to rearrange some lighting in my loading room
to ensure the ball was resting on the flat. I used a straight edge, or ruler, to ensure
that as the press ram was raised, the rod did not protrude above the top of the indenter
There is a picture in the instructions
that shows the bullet resting in the V block on a flat surface and the micrometer being
held against it for reading. This didnt work at all for me as there was too much
movement. When I secured the V block in an adjustable wrench for added weight, the
movement problem went away. I also experienced a problem with lighting. The incandescent
lighting in my loading room was insufficient for careful reading of the diameter of the
impression. By moving to the dining room with lots of natural light, that problem went
away too. The third difficulty was with my eyesight. According to Lee, I should be able to discern the impression edge
between the etched divisions, thereby reading the diameter to the closest .001 inch. I
couldnt. Even after solving the other problems, I dont believe I can see that
well, although younger or sharper eyes may not have a problem at all. I am able to read to
the closest division, i.e., to the nearest .002 inch, and thats probably within 1/2
BHN or so and close enough for our purposes.
The learning curve came into play
getting used to the kit and especially the fact that objects seen in the microscope are
reversed and any movement must be in the opposite direction. Over time, I went from
complete failure to a consistent misreading of the impression diameter to success.
My approach was to measure the hardness
of a bullet on the LBT tester. I would then file a flat on the same bullet and repeat
using the Lee tool. With the LBT tester I always took three readings and averaged them. With the Lee, I took one or
more and referred to the chart. During the misreading phase, I constantly got a higher
reading using the Lee kit due to, I think, the lighting and eyesight problems. If the LBT
reading gave me a BHN of, say, 14, as it did with several bullets, I consistently recorded
15.4 BHN with the Lee. Over time I was able to overcome the problems and the learning
curve until a three impression average with the LBT tool gave me a BHN of 16.6 on a
particular bullet. A careful testing with the Lee gave me a diameter of .056 inch. The
chart equates that diameter to a BHN of 16.6! Keeping the caveats mentioned in mind,
Im satisfied the Lee Lead Hardness Testing Kit performs precisely as claimed and can
be a useful addition to our handloading bag of tricks.
Knowing the BHN of a batch of bullets
is, of course, useless unless you know how to relate it to performance. The secret is in
knowing that the BHN times a constant 1,422 equals the pressure, in pounds
per square inch, at which lead alloy bullets become malleable, that is, begin to obturate
to fill the barrel or chamber throat. Many experimenters have found that applying
sufficient pressure to cause slight obturation produced the best results (see Dave
Scovills reports in Handloader Nos. 142
and 165). The Lee recommended approach is to keep pressure to about 90 percent of that at
which obturation occurs. How and why is well documented in Chapter 10 of Richard
Lees Modern Reloading, Second Edition. It
is well worth reading.
A product test is not the place to
debate the merits of differing approaches or to search for common ground. Still, cast
bullet shooting is a fascinating field of study for the interested handloader. The new Lee
Lead Hardness Testing Kit is a logical first step on that intriguing journey.
For more information, contact Lee Precision,
4275 Hwy U, Hartford WI 53027; or online at: www.leeprecision.com.
R.H. VanDenburg, Jr.