In classes I always warn students about a potential hang fire. A hang fire is when you experience a slight delay between when you pull the trigger and when the round fires. Generally the delay would not be more than a second or two and generally less than that. They are more common when shooting reloaded or old ammunition.
When you experience any type of weapon malfunction the first thing you should do before clearing the weapon is to wait a few seconds to ensure you are not experiencing a hang fire.
Perhaps the most random and lucky thing about the hang fire I witnessed today was that it was caught on camera. A good friend was filming and another good friend was shooting. Here is the short clip. In this case the hang fire was really short… a delay of less than a second.
Below is a second video in which a hang fire was several seconds and it nearly killed a man.