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General Gun and Turret Information Pages

siloette.jpg (14058 bytes)
A drawing of the USS IOWA(BB-61)

A warship serves as a platform to carry its armament into combat.  It exists for no other reason.  As a type, the battleship was intended for offensive operations against other battleships and was designed to carry the heaviest of guns.  Secondary and anti-aircraft guns were also provided as a defense against attacking destroyers and aircraft.   The armament of the USS IOWA is arguably the finest ever conceived and produced.  The guns, their mountings and operating machinery were fashioned into a complex and sophisticated weapons system which after nearly half a century, is still the finest of its type afloat. whole_turret_cutaway.jpg (37716 bytes)The main armament of the IOWA is the 16in/45cal Mark 7 gun.  The IOWA class are the only battleships to mount this weapon which is a considerable improvement over the 16in/45cal guns mounted in the North Carolina and South Dakota classes.

The Mark 7 gun fires two basic rounds, a 2,700 pound AP (Armor Piercing) and a 1,900 pound HC(High Capacity) shore bombardment projectile.  Nine of these weapons are mounted in three 3-gun turrets.  They are designated 3-gun turrets, as opposed to triple turrets because each gun is mounted ion an individual slide with its own elevation drive.  A triple turret has a single slide providing bearing surfaces for all three guns and uses a common elevation drive.  Two turrets are located forward and one aft of the superstructure.

The gun is a lightweight, built-up type consisting of a liner, tube jacket, hoops, locking rings, a liner locking ring and a yoke ring.  Assembly is accomplished by heating and expanding each piece before sliding it into position over the tube.  When the components cool and shrink, a tight single unit is formed.  The liner is inserted from the breech end, while an electric shrink pit and its locking ring prevents expansion aft when the gun is fired.  The liner is rifled with ninety-six grooves, 0.15in deep, with a uniform right-hand twist of one turn every twenty five caliber's.16in_gun_cutaway.jpg (22935 bytes)

Each gun is mounted in an individual slide with its own elevating gear.  The gun assembly includes a breech mechanism, firing lock, gas ejector and yoke.  It is designed for removal from the slide and gun port without dismantling the turret.  The breech mechanism is a rotating Welin interrupted screw plug and Smith-Asbury swinging carrier type.  The screw box liner and breech plug are segmented with stepped screw threads arranged in fifteen sectors of 24 degrees each.  The first sector is blank followed by four threaded sectors and this pattern is repeated three times for a total of twelve threaded and three blank sectors.  The breech plug is locked16in50_mk7.jpg (41391 bytes) with a 24 degree rotation after the plug threads are engaged.  The firing lock receives a hand-inserted plug-like brass cartridge about the size of a 30 cal carbine shell loaded with FFG black powder.   There is a provision for electric or percussion firing of the prier when the breech is closed.  When the breech is opened after firing the bore is cleared automatically by a 175psi low-pressure air system from the gas ejector system.  The gun yoke is a large counterbalancing unit mounted on the gun shoulder providing seats for the recoil cylinder piston rod and counter recoil cylinder yoke rods.  

The nine gun assemblies are mounted in three turrets, all on the centerline with arcs of train providing fire concentration of nine guns on either beam, six guns forward and three guns aft.  The three turret assemblies are very similar in design and construction, the main difference being tin the depth of their structures.  Each consists of a gun house with rotating structure, a fixed structure, a barbette, magazines and associated equipment. 

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All of the information in these pages is from the two sources below:
Reference #1
*Muir, Malcolm, THE IOWA CLASS BATTLESHIPS, 1987, Sterling Publishing, New York.  ISBN 0-7137-17327
*Sumrall, Robert, F., IOWA CLASS BATTLESHIPS, 1988, Naval Institute Press, Annapolis.   ISBN 0-87021-298-2


The information herein is 1996-2016 to The Veteran's Association of the USS IOWA, all rights reserved or the sources are listed respectively. Questions about this web-site should be directed to John E. Schultz

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