There is a firearms instruction school called Front Sight not far from here. They probably have a thousand students a day out there.
Part of their training is clearing malfunctions so quite a few loaded rounds get cleared from guns.
They've had ONE go off when it hit the ground, last I heard. Pretty good odds.
But it seems like this one was badly crimped primers? Can you link the story so we can see the picture?
I've always wondered; just how effective is a crimped primer at doing whatever it is supposed to be doing? Do battlefield conditions really cause a chance of a primer to fall out?