Your own link notes that the armor is thinnest on the top. Tank armor is also thinnest on top and bottom which is why Copperhead shells aim for the top...shaped charges do the rest. https://en.wikipedia.org/wiki/Iowa-class_battleship Armor: Belt: 12.1 in (307 mm) on 0.875 in (22.2 mm) STS Bulkheads: Iowa/New Jersey: 11.3 in (287 mm) Missouri/Wisconsin: 14.5 in (368 mm) Barbettes: front 11.6 in (295 mm) side 17.3 in (439 mm) Turrets: front 19.5 in (495 mm) side 9.5 in (241 mm) rear 12 in (305 mm) roof 7.25 in (184 mm) Conning tower: 17.3 in (439 mm) Decks: main 1.5 in (38 mm) second 6.0 in (152 mm) splinter 0.63 in (16 mm) over machinery, 1 in (25 mm) over magazines
LOL............an neither had battleships guns since there was modern battleships Late 1880s or so the change over occur and so what if I happen to had misspoked as cordite reacted in the same manner as black power to hits in the magazines.
In fairness after the explosion aboard the Iowa some major "news" outlets referred to the propellant charges as "black powder".
Ok, I thought I remembered something said about it. It turns out they use cordite, but the small bag at the primer is black powder.