Did any navy test a discarding-sabot shell for a battleship-caliber gun?
Short answerNo official program is identified, but early British and American work suggests tests may have explored high-velocity diving shells for underwater damage.
NotesNo official battleship-calibre sabot programme is identified. Early sabot papers suggest that British and American testing may have occurred, but this is an inference rather than documented programme history. A diving projectile is one plausible purpose: a smaller, high-velocity body could pass through underwater protection and open a large flooding path near engineering spaces. That would pursue one of the two basic routes to sinking a ship, uncontrollable flooding instead of an uncontrollable fire. Protection between the hull and engineering spaces varies by ship, so the proposed effect cannot be generalised to every design.