Type 91 Armor Piercing Shell

Introduction

遠距離砲撃戦における秘密兵器「九一式徹甲弾」。
海中突入後急激に向きを変え、魚雷のように敵艦水線下に突き進み、喫水下を破砕する特殊徹甲弾です。
水中弾効果を高める形状設計のため、空気抵抗も減少して射程も延伸します。
戦艦・航空戦艦等が使用可能。

"The long range bombardment weapon known as the secret weapon "Type 91 Armor-Piercing Shell". This type of ammunition will spin rapidly after exiting the the gun's barrel, enters the water, and penetrate the target's armor below the waterline like a torpedo, crushing the hull of the ships. The shell's shape enhances underwater penetration while also improving the range by decreasing air resistance. Available for Battleship (BB), Aviation Battleship (BBV) etc."

Notes

Buildable.
(Jul 28 2014) Can now be equipped to Fast Battleships.

(Oct 10 2014) When equipped together with large caliber guns, daytime hit and firepower bonus when attacking [heavily armored enemy ships] and [installation type bosses]

(Jan 23 2015) Can now be upgraded into Type 1 Armor-Piercing (AP) Shell, through Akashi's Improvement Arsenal.

Rumored to increase critical hit chance (source needed, statement not present in wikiwiki)

Akashi's Improvement Arsenal

Type	Name	★	Resource							Day							2nd Ship	Note
										Sun	Mon	Tue	Wed	Thu	Fri	Sat
	Type 91 Armor-Piercing (AP) Shell	0	30	350	110	0	2/3	1/1	-	✓	✓	X	✓	✓	✓	✓	Hiei Kirishima	Upgrades to Type 1 Armor-Piercing (AP) Shell
		6					3/5	1/2	1x
		10					6/9	4/9	2x

See Also

九一式徹甲弾