Percussion cap
（重定向自Percussion primer）
The percussion cap, introduced circa 1820, was the crucial invention that enabled muzzleloading firearms to fire reliably in any weather. This gave rise to the caplock or percussionlock system.
Before this development, firearms used flintlock ignition systems that produced flint-on-steel sparks to ignite a pan of priming powder and thereby fire the gun's main powder charge (the flintlock mechanism replaced older ignition systems such as the matchlock and wheellock). Flintlocks were prone to misfire in wet weather, and many flintlock firearms were later converted to the more reliable percussion system.