 The alteration of the military flintlock to the percussion musket was easily accomplished by replacing the powder pan and steel "frizzen" with a nipple and by replacing the cock or hammer that held the flint by a smaller hammer formed with a hollow made to fit around the nipple when released by the trigger.On the nipple was placed the copper cap containing the detonating composition, now made of three parts of chlorate of potash, two of fulminate of mercury and one of powdered glass.The hollow in the hammer contained the fragments of the cap if it fragmented, reducing the risk of injury to the firer's eyes.