Mystery solved.
He just got back from the hospital and it turns out that it was a ricochet.
It just expanded in such a way that it looked like a spent casing when covered in blood and sticking through flesh...
The jacket tore off and flew back 30ish yards and still went through his hand,
lucky it hit his hand instead of his face.
Anyway, thanks for your input and concern, looks like he might need surgery to repair some tendons