The Firearm Blog shared an image from one of their users named Scott B. It shows a primer that has been ignited and a case ruptured apart.
As you can see, the primer has sharp vertical crease and the case has been completely demolished. So we can infer that the primer was ignited by something other than the firing pin, and the case was not supported by a barrel when the powder ignited. I’m sure if you got out a micrometer, you would see that the dimensions of that strange imprint on the right side of the primer precisely mirror that of a factory ejector from a Glock or M&P.
What is alleged is that the shooter was covering the ejection port to try and bobble the round into his hand. In doing so, the slide went forward and smacked the back of the primer. With the bullet trapped in place, the round exploded and his hand absorbed most of that force.
The lesson here is that the shooter was not 100% focused on maintaining control of his firearm. He was distracted by his attempt to save $.25 by not dropping his ammo in the dirt.
When you unload and show clear, leave your ammo on the ground until you have holstered your weapon. In fact, as a rule of thumb, never reach for anything or touch anything with your support hand while you’ve got a pistol in your dominant hand. The human body has a natural tendency to try to grab things with both hands, and when you’ve got a pistol in your hand you will tend to aim the pistol at whatever you’re looking at or reaching for.
Ammo’s cheap. Surgery is expensive. Always maintain positive control of your weapons.
Erik is a private gunsmith living in Boise and a retired veteran of the US Army (OIF 09-11). He maintains a firearms related blog at threegunguys.wordpress.com, where many of these articles can be found.