16"/50 caliber Mark 7 gun

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A cutaway of a turret mounting 16in guns

Yard workers hoist one of nine 16"/50 Mark VII gun barrels aboard the USS Iowa during her construction in 1942.

The Iowa class battleship USS Iowa (1980s configuration, note missile launchers amidships) fires a full broadside of her 16"/50 Mark 7 guns. Note the shock waves reflected in the ocean's surface on the firing side of the ship; these are due to muzzle blast and not from movement of the ship.

The 16"/50 caliber Mark 7 - United States Naval Gun is the main armament of the Iowa-class battleships. Due to its power and efficiency, it is sometimes considered to be one of the best battleship guns ever designed.^[1]

Due to a lack of communication in the design phase, the Bureau of Ordnance assumed the Iowa class would use the 16"/50 Mark 2 guns constructed for the 1920 South Dakota-class battleships. However, the Bureau of Construction and Repair assumed that the ships would carry a new, lighter, more compact 16"/50 and designed the ships with barbettes too small to accommodate a 16"/50 Mark 2 triple turret. The new 16"/50 Mark 7 was designed to resolve this conflict.

[edit] Super-heavy shell

The Mark 7 gun was originally intended to fire the relatively light 2,240 pound (1,016 kg) Mark 5 armor piercing shell. However, the shell handling system for these guns was redesigned to use the "super-heavy" 2,700 pound (1225 kg) APC (Armor Piercing, Capped) Mark 8 shell, before any of the Iowa-class battleships were laid down.

The North Carolina and South Dakota classes used the preceding 16"/45 caliber Mark 6 gun which could fire the same "super-heavy" 2,700 pound shell as the Mark 7. However, the Mark 6 had a significantly shorter range, though this would not have likely proved a disadvantage in battleship duels. The Mark 6 gun was lighter, which helped both battleship classes to conform to the limits of the Washington Naval Treaty.^[2]

The heavier 2,700 pound projectiles made the Mark 7 guns nearly the equal in terms of penetration power to the 460 mm (18.1 in) guns of the Japanese Yamato-class battleships, yet weighed less than three-quarters as much. The Mark 8 shells gave the North Carolina, South Dakota, and Iowa classes the heaviest broadside among all battleships, save for the Yamato-class super dreadnought, and this was impressive considering that the North Carolina and South Dakota were treaty battleships.

The Mark 5 shells nonetheless were still a useful upgrade for the 16"/45 (40.6 cm) Mark 5 guns (formerly Mark 1 until reconstructed) of the Colorado-class battleships over the original 2,110 lbs. (957.1 kg) AP Mark 3 shells.

The propellant consists of small cylindrical grains of smokeless powder with an extremely high burning rate. A maximum charge consists of six silk bags, each filled with 110 pounds of propellant. ^[3]

[edit] Construction

The weapon is constructed of liner, tube, jacket, three hoops, two locking rings, tube and liner locking ring, yoke ring and screw box liner. Some components were autofretted. Typical of United States naval weapons built in the 1940s, the bore was chromium plated for longer barrel life. It uses a Welin breech block that opens downwards and is hydraulically operated. The screw box liner and breech plug are segmented with stepped screw threads arranged in fifteen sectors of 24 degrees each.

[edit] See also

Wikimedia Commons has media related to:

Category:16"/50 caliber Mark 7 gun

• List of artillery#Naval guns
• List of World War II artillery
• 18.1"/45
• Armament of the Iowa class battleship

[edit] References

1. ^ 16"/50 (40.6 cm) Mark 7 (html) (2007-09-17). Retrieved on 2007-11-21.
2. ^ http://www.navweaps.com/Weapons/WNUS_16-45_mk6.htm
3. ^ New York Times "Iowa Blast Inquiry: Long Search Ahead "

[edit] External links

• NavWeaps