Description of Jams
Failure to Fire:
Simply put the trigger is pressed and the gun does not fire. While this is normally a cartridge malfunction it can sometimes be indicative of an issue with the firearm itself. This is also known as a light strike.
Failure to Feed:
A failure to feed occurs when, on the slide's/bolt's forward stroke, the cartridge in the magazine does not full enter the chamber and the gun does not go into battery.
Failure to Extract:
The spent cartridge is not pulled out of the chamber and either remains in the chamber fully or partially leading to what is known as a double feed.
The action of the firearm tries to load a new round into the chamber but the spent cartridge remains in the action causing a jam.
Failure to Eject:
The cartridge fails to be thrown clear of the action on the ejection cycle. This results in what is sometimes known as a stovepipe jam where the spent casing ends up trapped between the breach and rear of the chamber with the majority of the case sticking out of the ejection port.