Japan's 100 mm gun combined high elevation with rapid fire for fleet air defense. Its original 70-calibre design wore out too quickly, and the revised 65-calibre weapon entered service in 1942 after being designed in 1937. Ammunition supply normally held the firing rate near fifteen rounds per minute, with nineteen possible when the hoists worked well, despite higher theoretical figures for the breech mechanism. The mounting could elevate from minus 10 to plus 90 degrees. Its lighter shells were less effective against destroyers and larger surface targets, where rapid damage could stop an opponent from fighting back. Wider fitting as secondary armament on cruisers and capital ships would have strengthened Japanese air defense, while destroyers still needed enough shell power for surface combat.
Chapter · 3:50-12:06
Japan's 100 mm gun and the air-defense tradeoff
Japan's high-angle 100 mm weapon offered excellent anti-aircraft performance but less surface punch for destroyer combat.