M.L. McPherson, June 2005
Efficiency: Why Case Shape Matters
Synopsis: While it has taken more than 150 years, today's shooters can begin to realize the benefits of cartridges that are designed for maximum efficiency. These advantages include increased barrel life, superior accuracy, reduced felt recoil, and reduced barrel heating. Since, in hindsight, the reasons that case design matters are easily understood, the question becomes: "Why did this take so long to figure out?"
Let us consider a conventional sporting, centerfire cartridge. Experienced shooters know instinctively that, for any given bore size, a larger case accelerates any given bullet to greater muzzle velocity. Similarly, it is obvious that, all else being equal, loading to increased pressure results in greater muzzle velocity. However, overall efficiency is in the details of case shape.
Sequence of Events when a Cartridge Fires
What
may not be so obvious is what actually happens when a cartridge fires.
Here we will review a somewhat simplified version of events that occur
after the firing pin strikes the primer.