primers
 

I looked over using a jewlers scope those hulls that were not pierced and there was a drag line visible, slight, on the primer. I suspect the pin was embedded in the primer as noted above.

Over on another reloading forum it's claimed Cheddite primers pierce more than others. It's all I use and out of ten SxS's only the right barrel on my Parker hammer gun will sometimes pierce one. The Noble and Fiocchi primers have a slightly larger diameter and once used, our American primers may not fit tight.