In a best case scenario, a squib load can be detected at the time of shooting and safely cleared in order to safely resume shooting. In a worst case scenario, a squib load can go undetected and blow your gun up (which by the way, is in your hand!).
Here’s a quick video that we shot at an informal “outlaw” steel shoot that just so happened to catch a squib load being fired. We recommend keeping a “squib rod” (typically brass, but a wooden dowel works, too) of the exact size caliber you’re shooting in your range bag for effective clearing of a squib round in the barrel. This prevents an undersized rod from having “play” or room to move around while clearing the rounds which could potentially damage the rifling on the inside of your barrel.
Here’s the clip: