<P> Berdan primers are similar to the caps used in the caplock system, being small metal cups with pressure - sensitive explosive in them . Modern Berdan primers are pressed into the "primer pocket" of a Berdan - type cartridge case, where they fit slightly below flush with the base of the case . Inside the primer pocket is a small bump, the "anvil", that rests against the center of the cup, and two small holes (one on either side of the anvil) that allow flash from the primer to reach the interior of the case . Berdan cases are reusable, although the process is rather involved . The used primer must be removed, usually by hydraulic pressure or a pincer or lever that pulls the primer out of the bottom . A new primer is carefully seated against the anvil, and then powder and a bullet are added . </P> <P> Meanwhile, Colonel Edward Mounier Boxer, of the Royal Arsenal, Woolwich, England was working on a primer cap design for cartridges, patenting it in England on October 13, 1866, and subsequently received a U.S. patent for his design on June 29, 1869, in U.S. Patent 91,818 . </P> <P> Boxer primers are similar to Berdan primers with one major difference: the location of the anvil . In a Boxer primer, the anvil is a separate stirrup piece that sits inverted in the primer cup providing sufficient resistance to the impact of the firing pin as it indents the cup and crushes the pressure - sensitive ignition compound . The primer pocket in the case head has a single flash - hole in its center . This positioning makes little or no difference to the performance of the round, but it makes fired primers vastly easier to remove for re-loading, as a single, centered rod pushed through the flash hole from the open end of the case will eject the two - piece primer from the primer cup . A new primer, anvil included, is then pressed into the case using a reloading press or hand - tool . Boxer priming is universal for US - manufactured civilian factory ammunition . </P> <P> Boxer - primed ammunition is slightly more complex to manufacture, since the primer is in two parts in addition to the pressure - sensitive compound, but automated machinery producing primers by the hundreds of millions has eliminated that as a practical problem . And while the primer is one step more complex to make, the cartridge case is simpler to make, use, and reload . </P>

Where do we find the priming mixture in a typical center fire cartridge