Hang fire refers to an unexpected delay between the triggering of a firearm and the ignition of the propellant.[1] This failure was common in firearm actions that relied on open primer pans, due to the poor or inconsistent quality of the powder. Modern weapons are susceptible, particularly if the ammunition has been stored in an environment outside of the design specifications. The delay is typically too brief to be noticed, but may be disruptive in processes where accurate timing is important, such as synchronization gear in propeller driven aircraft.
A hangfire should be suspected whenever a weapon fails to fire, but has not clearly malfunctioned. In modern, serviceable weapons it is more likely that the round is a "dud" (one that will never fire at all), but it is important not to immediately remove the round from the chamber. If a hangfire has in fact occurred, a round detonating outside of the weapon could cause serious fragmentation injury. If the operator believes that the weapon correctly cycled a fresh round and the action is not visibly jammed, the correct procedure is to keep the weapon pointed at a safe target for sixty seconds, then remove and safely discard the round.
The phrase "to hang fire" also means to delay in progressing, for example from one task to another.[2]