Percussion caps varied in material and style. Generally, though, percussion caps were manufactured from brass or copper with one end sealed and one end open to allow it to be mounted onto the nipple. The sealed end contained a shock-sensitive explosive which, when struck by the hammer, would ignite the powder in the cartridge through a series of sparks or flames which would travel down the hollow nipple (upon which the cap was mounted) and lit the powder.
Percussion caps would also vary in size, generally to fit to the size of the nipple. This meant that a variety of caps became available, designed for both pistols and rifles. Sizes would also vary due to the amount of explosive was needed to ignite the powder. A percussion cap was most often used with a paper cartridge (as it was the simplest way to ensure the ignition of the powder) although the basic concept would be integrated into modern metallic cartridges.
The major factor behind the percussion cap was the discovery of fulminates (chemical compounds that are unstable, hence causing them to explode in friction and impact enviroments) by Edward Charles Howard in 1800. In 1807 a Scott by the name of Rev. Alexander John Forsyth (Aberdeenshire, Scotland) managed to patent a design which eventually evolved into the percussion cap. There are debates as to whom exactly designed the first metallic percussion cap.The percussion cap was first introduced in the early 1820's, with one of the first firearms to benefit from the innovation was the M1819 Hall Rifle (which was quickly changed from the conventional flintlock configuration to the percussion lock design at the same time). The American based Springfield Armory were slower to take up the concept of using percussion lock mechanisms (their counterpart Harpers Ferry manufactured the Hall Rifle and continued to build percussion lock designs alongside the continued line of flintlock muskets), the Model 1842 Musket being their first percussion rifle.
In Europe, most development went into producing a reliable bullet designs that worked with rifling efficently. Therefore it took until 1836 before the first purpose built design to use percussion caps from Britain was the Brunswick Rifle, while the infamous Brown Bess saw widescale conversion. Eventually percussion cap utilising firearms would dominate most of the world's combat, with the American Civil War highlighting the efficency of the design.
The percussion cap has been used in a variety of applications, although most of these have been military concepts. Some of the world's most famous firearms were designed or converted to use the percussion cap.
The list below outlines the most famous (and significant) percussion cap using firearms (in chronological order):
- Brown Bess - Large numbers of conversion in the 1820s and 30s
- M1819 Hall Rifle - Possibly the first purpose built percussion lock firearm
- Brunswick Rifle - First British built percussion rifle
- Model 1842 Musket - Springfield Armory's first percussion lock firearm
- Pattern 1853 Enfield - Britain's most famous percussion rifle
- Springfield Model 1861 - Perhaps the most famous of the percussion rifles, used extensively during the American Civil War
- Sharps Rifles - The early members of the Sharps rifle series of rifles utilised percussion caps.
The percussion cap has also had an influence in the development of booby traps. Most military designed concepts use a spring-loaded firing pin that fires into a percussion cap, setting off an explosive. The USSR in particular developed this concept.
http://www.oldammo.com/december07.htm - Full colour version of the image available