| Hoisting 1 of USS Iowa’s (BB-61) 9 16”/50 Mark 7 main battery guns on board, while she was fitting out, at the New York Navy Yard, circa Autumn 1942. Another gun is still on the pier, at the bottom of the photo. More powerful than the 16 inch/45 caliber (406 millimeter) Mark 6 guns used on the North Carolina (BB-55) and South Dakota (BB-57) classes, this was possibly the best battleship gun ever put into service. Originally intended to fire the relatively light 2,240 pound (1,016.0 kg) Armor Piercing Mark 5 projectile, the shell handling system for these guns was redesigned to use the “super-heavy” 2,700 pound (1,224.7 kg) Armor Piercing Mark 8 before any of the USS Iowa class (BB-61) battleships were laid down. This heavier projectile made these guns nearly the equal in terms of penetration power to the 460 millimeter (18.1-inch) guns of the Japanese Yamato class battleships, yet they weighed less than 3/4 as much. As modernized in the 1980s, each turret carried a DR-810 radar that measured the muzzle velocity of each gun, which made it easier to predict the velocity of succeeding shots. Together with the Mark 160 Fire Control System and better propellant consistency, these improvements made these weapons into the most accurate battleship-caliber guns ever made. For example, during test shoots off Crete in 1987, 15 shells were fired from 34,000 yards (31,900 meters), 5 from the right gun of each turret. The pattern size was 220 yards (200 meters), 0.64% of the total range. 14 out of the 15 landed within 250 yards (230 meters) of the center of the pattern and 8 were within 150 yards (140 meters). Shell-to-shell dispersion was 123 yards (112 meters), 0.36% of total range. The Armor Piercing (AP) shell fired by these guns is capable of penetrating nearly 30 feet (9 meters) of concrete, depending upon the range and obliquity of impact. The High Capacity (HC) shell can create a crater 50 feet wide and 20 feet deep (15 x 6 meters). During her deployment off Vietnam, USS New Jersey (BB-62) occasionally fired a single HC round into the jungle and so created a helicopter landing zone 200 yards (180 meters) in diameter and defoliated trees for 300 yards (270 meters) beyond that. A persistent anecdote is that the Iowa class suffered from alignment problems until after the Battle of Leyte Gulf. William Jurens (Born ????), a noted expert on United States Navy naval weaponry, together with Iowa crewmembers and the staff at Naval Surface Warfare Center Dahlgren, performed a search of the official records for detailed data on this specific problem, but could find nothing in the files suggesting that the alignments were in any way out of the ordinary. Jurens’ suspicion is that there may have been an oblique reference to an alignment problem in some document that was taken out of context; perhaps they were waiting for parts. The Iowa class battleships were the last survivors of the battleship era to be placed into service, but they now exist mainly as memorials. The big-gun battleship era ended on May 16, 1991, when USS Wisconsin (BB-64) emptied her barrels for the last time. The weapon is constructed of liner, A tube, jacket, 3 hoops, 2 locking rings, tube and liner locking ring, yoke ring and screw box liner. Some components were autofretted. As typical of United States Navy weapons built in the 1940s, the bore was chromium plated for longer barrel life. The weapon used a Smith-Asbury Welin breech block which opens downwards. The screw box liner and breech plug are segmented with stepped screw threads arranged in 15 sectors of 24 degrees each. A manually operated lever is used to rotate and unlock the breech plug, which is then pulled opened manually. After loading, the breech plug is swung back up into the breech by a pneumatic system. The manually operated lever is then used to rotate and lock the breech closed. When the plug is locked, the breech lever engages the salvo latch mechanism which prevents the breech from being opened again until after the gun fires. | |
| Image Filename | wwii1866.jpg |
| Image Size | 177.31 KB |
| Image Dimensions | 1104 x 876 |
| Photographer | |
| Photographer Title | United States Navy |
| Caption Author | Written or Adapted by Jason McDonald |
| Date Photographed | September 1, 1942 |
| Location | |
| City | New York |
| State or Province | New York |
| Country | United States |
| Archive | Naval History and Heritage Command |
| Record Number | 80-G-K-513 |
| Status | Caption ©2026 MFA Productions LLC Please Do Not Duplicate or Distribute Without Permission; Image in the Public Domain |
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