What was the Imperial Japanese Navy's best destroyer gun?
Short answerThere was no unqualified best choice: the heavier guns handled slowly, while the 100 mm weapon was lighter and suffered serious barrel-wear penalties.
NotesThe Imperial Japanese Navy did not possess one clearly superior destroyer gun. Its heavier weapons followed a German-like preference for powerful shells that crews could not reload especially quickly. The 100 mm gun was a credible alternative, but it was light for a Second World War destroyer's main battery. A later comment also notes its rapid barrel wear, showing that rate of fire and service life mattered alongside calibre.