A percussion cap is a small metal cap containing a sensitive explosive compound, typically used in firearms. It is placed on the nipple of a muzzleloader or revolver, where it ignites when struck by the hammer. This ignition then ignites the main charge of gunpowder, firing the bullet. Originally developed in the early 19th century, percussion caps replaced the older flintlock ignition system, which relied on sparks. The invention of the percussion cap significantly improved the reliability and speed of firing firearms, making them more effective for military and civilian use, including hunting and sport shooting.