Misfires are by far most common with muzzleloading guns (most often with flintlocks), but they do occur in cartridge-firing guns. Should a misfire occur, shooters are well advised to keep the gun pointed in a safe direction for several seconds after the gun fails to fire, being prepared for a hangfire, and if the gun still fails to fire, then he/she may unload it carefully before proceeding.
Causes of misfires are many and varied. In examining a misfire, the first thing to assess is whether the gun performed its function properly. Did the firing pin strike the primer (or rim, on rimfire ammo) firmly and in the proper position? If not, a problem with the gun, magazine, or ammunition is interfering with proper operation of the firearm. If the firing pin struck the primer or rim properly and firmly, then the ammunition is probably at fault.