German sub-machine gun ammo

I have first hand knowledge of a Luger receiver blow up. A few years ago I ordered a Luger from an acqaintance who no longer lived in my area. He decided to shoot up some ammo he had before sending the Luger to me. After a few shots the receiver came apart. He required numerous stitches to fix his hand. He was using some foreign ammo. Later he looked at the box "for SMG use only" I know this happened because I lost a Luger and saw his hand some months later.