That'll teach me!
I was cleaning brass today and had run a batch of .357's through the cleaner and tumbler. As I was depriming them, on the down stroke of the loading press handle I felt "grit" and heard a POP!
Lifted the handle back up and found this:
Looked at the depriming die and of course the decapping pin was broken off.
Then I looked into the cartridge and saw this:
This was some of the brass I had picked up on the range. It had a nice little rock wedged in it! And no, I had not checked them.
~sigh~
I have plenty of spare parts and had it going again soon. But you know, I should have caught that.