16-inch/45-caliber Mark 6 gun

16-inch/45-caliber Mark 6 gun was the primary naval artillery weapon for the United States Navy's most powerful battleships of the World War II era. Designed as a lighter, more efficient successor to earlier heavy guns, it armed the ''North Carolina''-class and ''South Dakota''-class fast battleships. The gun saw extensive combat service in the Pacific War and the Korean War, providing formidable long-range fire support for amphibious operations.

Design and development

The development of the Mark 6 was initiated in the mid-1930s under the constraints of the Second London Naval Treaty, which limited new battleship gun caliber to 14 inches. The Bureau of Ordnance and designers at the United States Naval Gun Factory began work on a new 16-inch weapon that was significantly lighter than the preceding Mark 1 used on the Colorado-class battleship. When the Empire of Japan refused to sign the treaty, an "escalator clause" was invoked, allowing the United States and the United Kingdom to increase caliber to 16 inches. This allowed the finalized Mark 6 design, which featured a simplified, lighter construction using "A" tube and jacket construction, to proceed for installation on the new fast battleships. The design aimed to provide the hitting power of the older guns with reduced weight to meet new warship displacement limits.

Description

The Mark 6 was a 45-caliber breech-loading weapon weighing approximately 192,310 pounds including its Welin breech block. It fired two primary types of projectile: a 2,700-pound armor-piercing (AP) shell and a 1,900-pound high-capacity (HC) shell, using a standard propellant charge in six bags. The gun utilized a hydraulic rammer and was mounted in three-gun turrets, designated Mark 6 for the North Carolina class and an improved Mark 8 for the South Dakota class. Its maximum elevation of +45 degrees gave it a range of over 41,600 yards. The gun barrel was constructed with a liner that could be replaced after significant wear, extending the weapon's service life.

Service history

The Mark 6 entered service in 1941 aboard the USS ''North Carolina'' and subsequently equipped all ships of the North Carolina and South Dakota classes. These battleships formed the core of the Fast Carrier Task Force's anti-aircraft screens and provided heavy gunfire support during numerous amphibious assaults. Key engagements included the Battle of Guadalcanal, where the USS ''Washington'' used its Mark 6 batteries to decisively engage the Japanese battleship ''Kirishima'' during the Naval Battle of Guadalcanal. The guns were heavily used in the Marianas, the Battle of Leyte Gulf, and the Battle of Iwo Jima, bombarding fortified positions on islands like Saipan and Okinawa. After World War II, the USS ''Missouri'' and other ''Iowa''-class battleships with different 16-inch guns saw action in the Korean War, while the Mark 6-armed ships were placed in reserve fleet before being scrapped.

Variants

The primary variant was the **Mark 6 Mod 1**, the original production model. A minor modification, the **Mark 6 Mod 2**, incorporated slight changes to the breech mechanism and rifling design based on early service experience. The guns were exclusively paired with their specific turret models: the Mark 6 turret on the North Carolina class and the Mark 8 turret on the South Dakota class. The turrets themselves had different internal arrangements and armor layouts, but the guns and their ballistic performance were identical. No major redesigns or caliber changes were made during production.

Surviving examples

Several Mark 6 gun barrels survive as memorials and museum exhibits. One barrel is mounted at the Fallen Soldier Memorial in Warsaw, Indiana. Another is displayed at the Veterans Memorial Park in Bristol, Rhode Island. A gun from the USS ''Alabama'' is part of the Battleship Memorial Park in Mobile, Alabama, where the ship itself is a museum. The most intact examples remain aboard the preserved battleships USS ''North Carolina'' in Wilmington, North Carolina and USS ''Massachusetts'' in Fall River, Massachusetts, where visitors can view the turrets and guns in their original configurations.

Category:Naval guns of the United States Category:World War II naval weapons Category:406 mm artillery