this characteristic. Note that the final pyrotechnic flash generates a roughly cylindrical column perhaps 8-inches in diameter and about 18-inches long. Those who understand how a high-pressure jet propagates through and beyond an orifice (the flash hole) will instantly recognize this picture as representing an impossible situation, impossible, that is, if the produced jet is composed of final reaction products. Such a jet would generate a relatively longer and thinner, cone-shaped plume. For purposes of the following discussion, one can envision the plume as being made up of a relatively small volume of gas and particles blasted into the propellant chamber and then rapidly expanding many times in volume through decompression, and generation of additional heat and gas molecules.
Primers in the Real World
The
effectiveness of priming in conventional sporting cartridge is constrained
by several factors. In typical rifle loads and in most revolver and
pistol loads, using a reasonably full case of typical propellant,
any primer blast containing sufficient energy to theoretically carry
effective ignition to the bullet base would necessarily also dramatically
compress the charge toward the front of the case and might even pulverize
a significant percentage of granules that happen to be proximal the
flash hole. These two factors would necessarily work to defeat the
implied purpose for using such a primer. Specifically, increasing
energy of a conventional primer tends to increase both percentage
of granules that the blast might pulverize and total compression of
forward portion of charge.