Time for a little terminology that all shooters should know: (1) stoppage; (2) hangfire; (3) cookoff; and (4) dud.
1. Stoppage -- any unintended interruption in the cycle of operation of a firearm. Example: A failure to feed (FTF) is a stoppage.
2. Hangfire -- the firing pin hits the primer, but the primer does not go off immediately to initiate the powder charge. This can result from environmental conditions related to poor storage or age or a bad primer. Solution: Hold the firearm on target for 30 to 45 seconds. (If the round is going to fire, it will do so within this time period.) If the round does not fire, then it becomes a cookoff or a stoppage.
3. Cookoff -- this is the firing of the cartridge from the heat of the barrel itself. The cookoff becomes a consideration, especially in full auto weapons. When the bolt closes, the barrel is hot from extended firing, and the loaded round does not fire -- this is a potential cookoff situation. A very, very hot barrel (resulting from sustained fire from a machine gun) makes it essential to clear the malfunctioning round from the chamber immediately after the hangfire period has expired. During this time, the firearm MUST stay on target in case the cartridge becaomes a cookoff (that is, it fires) from the heat. If the barrel is NOT hot enough to cause ignition of the primer and powder from barrel heat, then it is a Stoppage. Go ahead and extract and eject the malfunctioning round.
4. Dud -- a cartridge where attempts have been made several times to fire it with the firing pin. For centerfires, this is reloading the malfunctioning cartridge into the chamber and having the firing pin strike the primer cap several times. For rimfires, this amounts to reloading the malfunctioning cartridge so that the firing pin will strike the rim about 90 degress from the first strike; then trying 180 degrees from the first strike; then trying 270 degrees from the first strike. If the cartridge doesn't fire after about four tries, the round has a bad primer and should be disposed of. Burning is probably the easiest way (making sure you aren't standing near the fire). On public ranges, just throw the dud round in the Dud Box.