107
ASPC were fi nally absorbed by their
fi nancial benefactors, Lafl in & Rand around
the turn of the century. During the last
decade of the 19th century other black
powder millers such as Du Pont also made
great strides in modern propellant design.
However, the longest surviving designs
must be Lafl in & Rand’s Bullseye and
Unique, later licensed to the Hercules
Powder Company.
TAKING CONTROL
Whilst the active chemical ratios are at the
heart of the propellants performance, they
require the addition of further chemistry in
order to make them more user friendly. We
know that camphor was an early stabiliser
and that its evaporative loss led to the
dangerous decomposition of the
propellant. Dozens, if not hundreds of
other binders, wetting agents and
stabilizers have been used over the
following years. External coatings have
been added to reduce the build-up of
static, improve metering and modify the
rate of defl agration.
An example of an early performance
enhancement is good old Alliant Unique.
It’s 115 years old and still going strong,
but it is rather unsophisticated. The
external deterrent coating has a graphitic
base and needs a fairly brutal bang to get
it started. Used in a low pressure light
target load with a modest crimp it is not
unusual to get a residue of clear colloids
of partially combusted material. Use a
heavier bullet, a hotter primer and a big
crimp to generate a higher start pressure
and the residues often disappear. Some
propellants are more reactive to external
temperature changes than others but little
quantifi ed data exists, so just take care
and work on the simple premise that hot
loads will get the ‘hottest’.
Shape changes were, and still are, an
effective means of adjusting the rate of
defl agration. In simple terms, controlling
the surface area as the grain defl agrates
can increase, decrease or have no effect
on that rate. Most neutral is a rod with a
single hole, as the outside surface area
reduces, so the inside increases. To
achieve an increasing or progressive rate
the surface area needs to be increasing,
usually by means of multiple holes within
a rod or with a central perforation of
geometric shape, such as a star. Reducing
or degressive performance is achieved
from a plain ball or sphere, or a solid rod
or fl ake.WHAT SPEED?
We’ve all seen, and probably tried to make
sense of charts illustrating powder burning
speeds. Well, they really only have limited
use, something that sometimes becomesobvious when you compare load data for
two ‘similar’ powders in both a small
capacity and a large capacity cartridge case.
It is not unusual to fi nd that the charge to
performance ratio of the two examples is
reversed. It’s not as bad as comparing
apples with pears, but in truth we’re often
trying to compare Bramleys with Strawberry
Normans or Golden Delicious. The charts
can put you in the right ball park but must
never be used for data interchange.Early Laflin & Rand poster Extremely early can of Ballistite made under license by Du Pont Rare container of Schultz Powder; it’s amazing what is collectable these days
The explosive in front of your face - a
nitroguanidine detonator used in a car’s
airbag system