On
primer cup

Primer - is an igniter used to initiate the burning of a propellant. Small arms cartridges are classified as centerfire or rimfire depending on the location of the primer. In centerfire cartridges, the primer is located in the center of the base of the cartridge case. There are two types of primers for metallic cartridges, Boxer and Berdan.American centerfire rifle and pistol cartridges have boxer primers,(blazer ammunition is the exception)A boxer primer consists of a brass or gilding-metal cup, a pellet containing a sensitive explosive, a paper disk, and a brass anvil. These component parts are assembled to form a complete primer. The boxer primer has a single large flash hole in the bottom of the case.

     European metallic cartridges traditionally are loaded with Berdan primers. The Berdan primer differs from the American boxer primer in that it has no integral anvil. Instead, the anvil is built into the cartridge case and forms a projection in the primer pocket. Berdan primers have two flash holes in the primer pocket.

     Shot-shell primers are a variant of boxer primer used in metallic cartridges. The main difference is that the shot-shell primer has its own supporting cup, the battery cup, which encloses the anvil, the paper disk, the priming mixture, and the primer cup. This battery cup primer is inserted in the base of the shotgun shell.

     Primers made for rifles and pistols differ in construction in that the cups of pistol primers are made with thinner metal. The riffle primer also has a mixture that burns with a more intense and sustained flame.

Primers come in five sizes. They are
1. Large rifle
2. Small rifle
3. Large pistol
4. Small pistol
5. Shotgun
 
The large primers measure .210 inches in diameter, the small is.175 inches and shotgun primers are .243. Magnum primer (either rifle or pistol) produces a more intense and sustained flame which is necessary for better ignition in magnum cartridges.

     When a weapon is fired, the firing pin strikes the center of the primer cup.compressing the primer composition between the cup and anvil and causing the composition to explode. The vents in the anvil allow the flame to pass through the flash hole into the cartridge case and thereby igniting the propellant.

     Primer compounds originally were made of fulminate of mercury. On firing, free mercury is released. This amalgamated with the brass of the cartridge case, making it brittle and ruining it for reloading. In addition, storage of ammunition containing mercury primers for long periods of time led to the deterioration of the brass because of the mercury. Mercury compounds were then replaced with chlorate compounds. Unfortunately, on firing, these break down to chloride salts, causing severe rusting of the barrels.
 
     All primers currently manufactured in the U.S. use chemical ingredients that are non-mercuric and non-corrosive.The compounds that are used vary, lead styphnate, barium nitrate, and antimony sulfide are most commonly used. Most centerfire primers of either U.S. or foreign manufacturer contains all three compounds. The detection of these compounds constitutes the basis for tests to determine whether an individual has fired a firearm. Blound industries (CCI), Remington, Federal, and Winchester now manufacture some centerfire pistol ammunition that does not contain lead in the primer.

     Rimfire ammunition does not contain a primer assembly. Instead, the primer composition is spun into the rim of the cartridge case with the propellant in intimate contact with this composition. On firing, the firing pin strikes the rim of the cartridge case compressing the primer composition and initiating its detonation. The priming mixture used in .22 rimfire ammunition manufactured by Winchester and CCI are compounds of lead and barium and antimony. Remington rimfire ammunition used to contain only lead compounds but now uses compounds of lead and barium. Some Mexican manufactured rimfire ammunition uses only lead compounds in the primer

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