15.5cm Triple Secondary Gun Mount
Introduction
巡洋艦の主砲だったものを、戦艦の副砲として活用しました。
「大和」型に搭載され、対空戦も可能な、性能・運用ともに優秀な戦艦副砲となりました。
砲塔部の装甲が薄いのが玉に傷で、諸説ありますが「大和」型の唯一の弱点という指摘もありました。
"Although designed to be a part of the cruiser's main battery, it saw a more practical use as the battleship's secondary armament. The Yamato-class was designed with this, for potential use as an anti-aircraft gun, however its combined ability and performance were outstanding enough to be used as the battleship's secondary armament. However, the turret section's armor was very thin, resulting in various rumors about it being the Yamato-class' Achilles' heel when pointed out."
Trivia
According to here, the Mogami-class and eventually the Tone-class was supposed to have the gun, but when the practical use was seen in Yamato-class and Oyodo, it then remained as part of the battleship's main weaponry. One factor for the gun design change was that the gun was supposed to have an additional 75 degrees for AA firing on top of the main 45 degrees for general firing, but this was switched to +55 degrees for the reasoning that it was too inefficient.
The "Achilles' heel" portion refers to the relatively inferior armour thickness of the turret part, albeit being colossaly improved compared to casemate guns of other Japanese battleships (Fuso-class to Nagato-class).
Note
See Also
15.5cm/60 3rd Year Type Naval Gun