Don't remember seeing this elsewhere. Might be of value to some folks.
MAKING BULLET ALLOYS
A lot has been written on bullet metals, but not much on making up
alloys with specific desired properties. Most bullet casters have
scrap and salvage lead alloys on hand which they wish to use. Can you
provide guidance for making up alloys from such metal to get a specific
product?
ANSWER: The following method does this. It is based on two
observations made during long-term investigation of cast bullet alloys
by the staff of The American Rifleman.
1. The characteristic of a bullet alloy which is most fundamental to
performance is strength, indicated by hardness.
2. The hardness of a mixture of usual lead alloys is approximately in
proportion to hardness of the separate alloys in it. This includes
straight lead, Brinell hardness 5, as a constituent.
Hardness of the salvaged alloys to be used therefore must be know. The
American Rifleman has given a simple method for measuring it: "Brinell
Hardness", January, 1969, p. 57; and "Brinell Hardness Measure",
December, 1974, p. 63-64.
The product having desired hardness is obtained by using the metals on
hand in quantities according to the hardness each supplies. One-lb.
pigs cast in the small iron molds sold to handloaders are most
convenient. The following was made up most recently, aiming at a
Brinell hardness of 15 and using three lots of scrap found to be of 20,
17«, and 12« Brinell hardness number respectively. These weights of
each therefore were taken:
WT. BHN
2 x 20 = 40
3 x 17 = 51
4 x 12.5 = 50
__ ___
9.5 141
The BHN to be expected from this calculation obviously is 141 / 9.5 =
14.8. The product should approximate this. In this case it actually had
a hardness of 16.5. Alloys made up by this method regularly show a
slightly greater hardness than their proportions indicate, which can be
allowed for in the make-up or accepted as being tolerably close.
The above proportions were arrived at by a few trial calculations.
These often show that a desired result can be obtained in more than one
way. Thus the method has considerable flexibility. For example, a
calculation with the same three available metals shows that weights of
1, 5, and 3 lbs respectively could be expected to produce an alloy of
(1x20 + 5x17.5 + 3x12.5) / 9 = BHN 16, close though a little harder than
wanted. If only the last two lots of scrap were on hand, 5 and 4 lbs.
of these could be expected to give (5x17.5 + 4x12.5) / 9 = 15.5,
practically the same as the alloy made above.
Thus a few trial calculations, with the simplest kind of arithmetic,
indicate at once the combination(s) of available metals which will make
an alloy of specified hardness, within the physical possibilities of
course.___E.H.H.
from CAST BULLET
Col. E.H. Harrison
NRA 1979, p. 90
..........END OF FILE..........
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Originally Posted by Stoddy
