Hang fires happen when the firing pin has struck the primer and there is a delay before the gun fires. This can occur for several reasons, such as a faulty firing pin or spring, defective primer, or other cartridge-related problems. A misfire is when the primer fails to ignite the powder. Hang fires and misfires can happen with any kind of firearm.
A "squib load" occurs when the projectile becomes stuck in the barrel and does not exit after firing. This can be extremely dangerous if another round is fired in the obstructed barrel.
Always treat a "misfire," a "hang fire," or a "squib load" as if the firearm is going to discharge at any second. Leave the action closed and retain your shooting position. Most importantly, maintain muzzle control in a safe direction at all times. Failure to follow these safe handling practices could result in a tragedy.