[flechero]

I'm guessing you didn't get it shoved all the way into the shellholder and the base of the expander hit the top and folded it down. I have done the same with a U-decap die on occasion. Be sure you push the case all the way into the shellholder (and be sure you press is level)

 

[flechero]

So is trying to bash a large primer into a small P case that got through security somehow! 😡

I hope you fire your security.
That can easily be solved by using all small primer 45 brass. I believe they're easier and cheaper to find too.

Kicked him square in the nuts!