Clark's makeshift 30-30 to 10mm...
Clearly the brass has started to shear and very near the point of ripping open. This would send jets of high pressured gases through out the openings of the firearm, with the largest opening being the magazine well which is surrounded by the shooter's hand and fingers! OUCH!
Sevens, thanks for the reconition.
I am glad your pistol, like mine benefited from the use of the 22# Wolff spring. I'd bet the OP will se the benefits as well!