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The Cartridge Case
By Chuck Hawks
Among the key components of a metallic centerfire cartridge (bullet, powder, primer, and case) it is the cartridge case that is by far the most expensive and durable. This simple fact is what makes reloading possible and practical.
The case is the "bottle" that holds the bullet (the "cork" if you will) at the front, the powder inside that powers the bullet on its trip down the barrel, and the primer in its base that sparks the burning of the powder when it is dented by the firearm's firing pin. The case not only holds everything together, it forms a gas seal crucial to the shooter's comfort and safety when the arm is fired. The high pressure generated by the expanding gasses released by the burning powder when a gun is fired cause the case to expand slightly, tightly sealing the chamber and preventing the blow-back of gas toward the shooter. The concept of the case is what made single chamber repeating firearms practical and immensely speeded reloading.
Cartridge cases have been made from copper, mild steel, aluminum, and brass.
Brass cartridge cases are formed from a round disc (called a "blank") of metal that is drawn to its ultimate shape in a series of steps.
Reloadable cartridge cases use a centrally located primer (thus "centerfire") of the Boxer type. Boxer primers use a self-contained anvil. Cases for use with Boxer primers have a single flash hole in the center of the primer pocket that allows the explosion of the primer to ignite the main powder charge. These are the cases that are normally reloaded, as the primer is easily removed (decapped) by a decapping pin centrally located in a reloading die. All U.S. made (and many European) brass cartridge cases use Boxer primers and are reloadable with standard reloading dies.