Three guns in each turret
The American technical investigation describes nine 46-centimetre guns in three triple turrets, two forward and one aft. Their bore diameter was about 18.1 inches. The misleading official designation, 40 cm/45 Type 94, concealed the actual calibre. The armour-piercing projectile weighed 1,460 kilograms—nearly a tonne and a half. YT-Y21
The report gives a maximum range of 45,960 yards at the installed maximum elevation of 45 degrees, and a firing rate of 1.5 rounds per minute at maximum elevation. These are reported technical capabilities, not a promise of hits at that distance or a measured firing rate during Yamato’s last battle.
What the investigators could examine
The investigators inspected guns and components and interviewed Japanese specialists. They had not seen a complete turret, still less one operating. Original drawings were unavailable to them; parts of their reconstruction depended on recollection and sketches made from memory. Their report therefore preserves unusually valuable detail without providing a complete independent performance trial. YT-Y21
Power that had to reach the battle
The April 1945 order directed the surface force towards the ships supporting the Okinawa invasion. It envisaged cooperation with other Japanese forces, rather than an isolated duel between battleships. YT-Y05
Carrier aircraft attacked before Yamato reached that intended engagement area. Miyamoto’s testimony describes repeated attacks, mounting damage and an increasing list without effective fighter cover during the decisive phase. Those conditions explain why a formidable main battery did not decide the outcome. They do not show that the guns would have been harmless had the ship reached surface targets. YT-Y01
Read Orders for Okinawa for the intended mission and What Could Yamato Have Changed? for the limits of that alternative.