I got a 12Lb CS sideloader with remains of the paper fuse in it. It burned all the way to the matrix - Since there was no place for a powder charge in the shell. They had filled it without the mandrel in place.

"Friday shell" would be my guess. A shell would have to be unloaded to fire that way as a bolt. That makes no sense since to fire as a bolt would be simple to send on it's way unfused - or at least with no cap on the nipple.