[Edit]
51cm Twin Gun Mount
No.281 51cm連装砲
| |
 Large Caliber Main Gun (II) (??)Effects:
 +32  +5  +2  +1  -1  Very LongScrap value:
 30  28 (Unbuildable) | |
| Refittable Class | |
| Coastal Defense Ship | Destroyer |
| Light Cruiser | Torpedo Cruiser |
| Heavy Cruiser | Training Cruiser |
| Aviation Cruiser | Fast Battleship |
| Battleship | Aviation Battleship |
| Light Carrier | Standard Aircraft Carrier |
| Armored Carrier | Seaplane Tender |
| Submarine | Aircraft Carrying Submarine |
| Submarine Tender | Fleet Oiler |
| Repair Ship | Amphibious Assault Ship |
Introduction
大和型戦艦の発展強化型への搭載が検討されていた大口径大型用戦艦主砲、その完成版です。最大最強の艦艇搭載用砲熕兵装となる本砲は、改装強化された大和型等で運用可能です。
実戦配備されることのなかった本砲で、海原で一斉射を！
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Notes
Unbuildable
Category Ships with 51cm Twin Gun Mount as stock equipment not found
Category Equipment that consume 51cm Twin Gun Mount during improvement not found
- Winter 2018 Event E-7 Medium/Hard reward.
Improvement
Improvement Cost:  100 700 950  200
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★ | 
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S | M | T | W | T | F | S | Helper Ship |
|---|---|---|---|---|---|---|---|---|---|---|---|
Consumes: 4x  41cm Twin Gun Mount
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0 | 20/25 | 7/8 | M | ✗ | ✗ | ✗ | ✗ | M | M | Musashi Kai Ni |
| Consumes: 4x 46cm Triple Gun Mount
|
6 | 25/50 | 10/13 |
Trivia
Officially known as the 51 cm/45 Type 98 naval gun, it was supposed to be used by the A-150 battleship design (or Yamato Kai) that were never built. 2 complete guns were finished just before the start of the Pacific War but since the A-150 battleships were never ordered, they were left in storage until the end of the war, where they were probably destroyed. Mechanically, they were the same as the 46 cm and constructed with the same techniques as the 46 cm.