Iowa-Class 1650 Mark 7 — America’s Most Powerful Battleship Guns WW2 Visual Archive The 16-inch/50 Mark 7 naval gun was the main battery of the United States Navy’s Iowa-class battleships — the most advanced and powerful American battleships of World War II. These massive triple turrets armed: USS Iowa USS New Jersey USS Missouri USS Wisconsin The guns could fire a 2,700-pound (1,225 kg) armor-piercing shell over 23 miles (37 km) with extreme accuracy. Their fire supported carrier groups, shore