One can easily prove that the ideal goal for ballistic efficiency and uniformity is to have every powder granule ignited before bullet movement begins. Consider that any granule that does not ignite at all or that does not ignite until the bullet has already exited the bore cannot contribute anything to bullet acceleration and that such a granule must absorb some of the energy that would otherwise contribute to bullet acceleration – either through granule heating or through granule acceleration or through both effects. Then consider that the sooner any given granule ignites, the longer the energetic gases generated by the resulting combustion will have to work on the bullet – more time, more work.
Since, in any conventional cartridge, it is fundamentally impossible to achieve ignition of all granules before the bullet begins to move, we opted for the next best thing – ignition of as many granules as soon as possible and uniform burnout of the remainder. For this reason, we optimized our design for several important characteristics, which work toward maximizing percentage of powder granules ignited at any point during bullet acceleration toward muzzle. The following characteristics apply.
1. An unusually
short and fat case design increases percentage of granules ignited
by primer.
2. A two-to-one ratio between case interior and bullet diameter
contributes to simultaneous burnout of plug and cylinder.
3. Single-radius
shoulder (body-to-shoulder radius only) helps trap cylindrical propellant
mass, thereby exposing this material to the highest possible pressure
(temperature).
(Owing to gas acceleration through the bore, pressure
drops as a function of distance from web. Combustion rate depends
upon pressure and granules entrained into the bore experience progressively
less pressure as those accelerate away from the chamber. Because powder
is a progressive-burning substance, this pressure differential results
in a significant difference in burning rate.)
4. Cylindrical mass trapping
also limits energy losses associated with acceleration of unignited
solids and the bore erosion such burning particles induce.
5. Elliptical
shoulder design minimizes primer-generated shock energy transfer to
bullet base. This minimizes potential for primer blast to prematurely
move bullet. This design also focuses waste energy from primer blast
into powder located directly behind bullet base (this portion of charge
is last to ignite and least contributory to bullet acceleration).
Resulting compressive heating speeds subsequent ignition and burning
of material within this mass.