Berdan Primers
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Berdan Primers |
Boxer Primers
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The "Boxer" system was invented by a British army officer Edward M. Boxer around 1880, but the system is used more in the USA than UK.
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 outer 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 separate
"anvil".
The pocket that the primer is located in is of small volume and thus the expanding gasses and flame are forced through the web of the anvil (usually three legs) and out of the single central hole in an intense jet of flame.
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 flame from the primer flash hole percolates through the spaces, causing immediate ignition of a large surface area of many of the propellant grains. Some powders are also porous in themselves to promote this rapid ignition.
I make no apologies for using "Imperial" dimensions in this part of the website, where they are appropriate, as metric conversion can lead to discrepancies which may become dangerous.
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The principle dimensions of American Boxer primers are shown in the table. Primer pocket depth varies a little from calibre to calibre, but is always a few thousandths of an inch deeper than the primer so that the resulting primed case has its primer seated under-flush with the case head base.
The primers for shotgun cartridges are often built on the principles of the Boxer primer, but are physically larger and more robust in construction. These vary greatly in form from manufacturer to manufacturer and in the main are not interchangeable.
Removing or de-capping of spent Boxer primers is covered on the Boxer Primer Removal page.
Written... 08 July 2001, Amended... 26 September 2002, New Domain... 19 November 2003, Upgraded... 24 January 2007,
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