cap and ball

The caplock mechanism, percussion lock, or cap and ball was the successor of the flintlock mechanism in firearm technology, and used a percussion cap struck by the hammer to set off the main charge, rather than using a piece of flint to strike a steel frizzen. The caplock mechanism consists of a hammer, similar to the cock used in a flintlock, and a nipple (sometimes referred to as a "cone"), which holds a small percussion cap. The nipple contains a tube which goes into the barrel. The percussion cap contains a chemical compound called mercuric fulminate or fulminate of mercury, whose chemical formula is Hg(ONC)2. It is made from mercury, nitric acid and alcohol. When the trigger releases the hammer, it strikes the cap, causing the mercuric fulminate to explode. The flames from this explosion travel down the tube in the nipple and enter the barrel, where they ignite the main powder charge.

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