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Flash Hole: One (Boxer) or more (Berdan) holes or a continuous
annular vent (rimfire) through
which generated "primer plume" produces
into "propellant column."
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Grain: Correctly in this context, a unit
of mass, equal to 1/7000 pound.
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Granule: Individual "propellant" particle.
(Much confusion can ensue when persons use the colloquial "grain"
to indicate a single granule; hence, this nimrod attempts to avoid
this usage.)
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Ignition Point Temperature: Local specific temperature
at which reaction of a material becomes "effectively exothermic."
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Hotter: In this discussion, representing a primer having more total
energy, particularly more "brisance."
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Plume Penetration Depth: Maximum
distance to which "primer plume" can heat a "propellant" granule sufficiently
to create "primary granule ignition."
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Porosity: Within a granular
solid mass, total volume not occupied by solid portion of granules.
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Permeability: Potential for gas or fluid to flow through a granular
solid – larger pore spaces and certain particle shapes tend to increase
this characteristic.
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Primer Plume: Developing "pyrotechnic gases"
generated through flash hole of cartridge case, after primer ignites.