"Not supposed to break" Right. I have broke plenty. Usually results from being too fast with military .223/5.56. I have better luck not giving a full on power drive the first push, if the pin starts to rise and primer doesnt budge, set that case aside. Once in awhile the pin may not be lining up with primer hole, from either manufacturing problem, or more likely, not set properly in shell holder. Order several spares.
Oh, and forget the little base and pin they sell to be used independent of a die. I broke 3 in a row, in the trash. It is supposed to be unbreakable, but I have way better luck with the universal die, or the pin in the full length sizing die than that thing.
Russellc