Source-checking the converted-shell story at Pearl Harbor

Were the Japanese armour-piercing bombs used at Pearl Harbor simply converted battleship shells?

The simple description is disputed: a purpose-built bomb body may still use shell-derived fuzing, and the live source check leaves the exact lineage unresolved.

The value of this exchange is its method and uncertainty rather than a tidy technical verdict. The initial answer rejects the simple conversion claim, then a live check of Type 80 and Type 99 designations finds descriptions linking a Mark 5 armour-piercing bomb to a 16-inch shell. A teardrop bomb body dropped from an aircraft does not need the structure or external form required to survive gun launch. An armour-piercing fuze or design concept could still pass from a shell into a purpose-built bomb. Participant corrections and the checked notes continue to conflict, so the passage works best as a source-criticism watch point rather than a final technical specification.