Mini Kaboom?

[Anti-Hero]

incipient case failure

[ireload]

Firing out of battery would be my least suspect since the primer has a good indentation from the firing pin. Plus you'll have soot deposited just outside the breech area of the barrel, slide, and parts of the magazine well. Very light powder charge (detonation), over worked brass (weakening) from hot reloads, or corrosion which can cause a pinhole or crack. I have the same pistol as yours and from the looks of it that would be hard for it to fire out of battery. Even new brass or commercial made ammo can have bad brass from time to time.

[xfer42]

Inspect the locking block. Make sure it didnt crack. Those are supposed to be replaced after about 5k rounds. They will/can last longer, but expect it to go anytime after the 5k mark.

[CEDaytonaRydr]

Firing out of battery would be my least suspect since the primer has a good indentation from the firing pin. Plus you'll have soot deposited just outside the breech area of the barrel, slide, and parts of the magazine well.