Hang fire
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The term hang fire refers to a state in which an unexpected delay is encountered between a firearm being triggered and the initiation of the propellant. This mode of failure was common in firearm actions which relied upon open primer pans, due to poor/inconsistent quality powder. Modern weapons are susceptible, particularly where the ammunition has been stored in an environment outside of the design specification. The delay is typically too small to be noticed, but may be disruptive in processes where accurate timing is important - as in synchronization gear in propeller driven aircraft.