Boxer Primers
Berdan Primer Dimensions
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Boxer Primers Berdan Primer Dimensions |
Berdan Primers
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The "Berdan" primer system was invented by an American ordinance officer named Hiram Berdan, around 1870 is the nearest date that I could establish, ironically the system is used more in the UK, Australia, South Africa and Europe than the USA where it originated.
The primer is the source of ignition for the rapid burning process that occurs in firearms.
The whole process starts from the percussion blow of a
hammer or firing pin. The metal cup of the primer is distorted by this
striking action causing the compression of the primer compound between
the cup's inner surface and the tip of the post, that is incorporated
in the structure of the case, which acts as an "anvil".
The pocket that the primer is located in is of small volume and thus the expanding gasses and flame are forced through holes numbering one two or three that are placed in a ring surrounding the central anvil post. This causes one two or three jets of flame with a correspondingly larger surface area than the single flame of the Boxer system.
The "flash holes" of Berdan primer recesses are usually smaller in diameter than those used for the Boxer types. The total area of the Berdan flash holes is less than for boxer types, ensuring that the resulting jets of flame are more intense, thus giving more reliable ignition.
As the propellant powder usually consists of regularly shaped, discs, rods or tubes, there are interstitial spaces between the particles (and in the case of tubular grains along the internal axis as well). The flames from the primer holes percolate through the spaces, causing immediate ignition of a large surface area of many of the propellant grains. Some powders are also porous in themselves which further promotes this rapid ignition.
This multi flame approach works well with Nitro cellulose cylindrical rod propellant (Cordite) which because of it composed of long thin rods that are almost the full length of the space below the bullet. It presents a smaller overall surface area to the ignition flame front, but the long thin spaces between the rods allows for a great deal more of this surface area to be exposed to the multiple flames.
I make no apologies for using "imperial" dimensions on this page, as metric conversion can lead to discrepancies which may become dangerous.
The principle dimensions of Berdan primers for specific manufacturers and calibres are given on the companion page that also attempts to provide information on Berdan primer suppliers.
Some cups that are made of bronze contain priming compounds that are corrosive.
I personally favour Berdan primers over Boxer The reliability and safety are better and the reloadability is no different in difficulty. A different method is needed, but I have never understood why our American friends whinge about the "difficulty" or "impossibility" of reloading.
Many solid brass shotgun cartridges are Berdan primed and many of the Cordite "big game" cartridges are also Berdan type.
The terms 'primer' and 'cap' are often used interchangeably, but the word cap is used more frequently with reference to Berdan than Boxer.
Removal of spent Berdan primers is dealt with on a group of pages that link from Berdan Decapping.
Written... 08 July 2001, Revised... 26 September 2002, New Domain... 22 November 2003, Upgraded... 24 January 2007, Revised... 30 April 2007,
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