page_title: 12"/45 caliber Mark 5 gun
section_title: Incident
hierarchical_section_title: 12"/45 caliber Mark 5 gun / Incident
caption_attribution_description: English: View looking aft along the port side, showing barrel of burst 12-inch gun on deck with the gun's rear portion in Turret # 2. Photographed at the Philadelphia Navy Yard, Pennsylvania, 25 September 1916. Note holes in superstructure and in the "cage" foremast caused by this accident.
context_page_description: The 12″/45 caliber Mark 5 gun was an American naval gun that first entered service in 1906. Initially designed for use with the Connecticut-class of pre-dreadnought battleships, the Mark 5 continued in service aboard the first generation of American dreadnoughts.
context_section_description: During the summer of 1916, Michigan blew out her left hand gun in turret No. 2 during target practice. After an investigation of South Carolina's guns it was discovered that copper deposits from the driving bands on the projectiles had narrowed the bores of the barrel enough that it caused the projectiles to slow down. This problem, known as "copper choke", allowed the pressure in the barrel to increase to dangerous levels. Lapping heads, to remove these deposits, were issued for all guns 12-inch and larger throughout the fleet. The lapping heads were later replaced by wire and pisaba brushes.
caption: View looking aft along the port side, showing barrel of burst 12-inch gun on deck with the gun's rear portion in Turret # 2. Photographed at the Philadelphia Navy Yard, Pennsylvania, 25 September 1916. Note holes in superstructure and in the "cage" foremast caused by this accident.
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