Many US Warships 1950s to 1980s

Exported to Japan where they were used on many DD and DDG ships

Spanish Andalucia class frigates

With the latest alterations:
   Single side operation:  17 rounds per minute
   Two side operation:  34 rounds per minute

RAP Mark 58 - 70.0 lbs. (31.75 kg)

1) Special Common Mark 42 had a windscreen and a thin hood and was strengthened to enhance its armor piercing qualities.  Mark 41 projectile bodies could be used with Point Detonating (PD), Mechanical Time (MT) or with proximity (VT) nose fuzes.  When used with PD fuzes, they were considered to be HC rounds while those with MT and VT fuzes were considered as AA rounds.  Rounds with MT or PD nose fuzes had an instantaneous contact type base fuze.  A blind plug was used in place of the base fuze for those projectiles using VT nose fuzes.

2) In addition to the above types, a laser-guided shell, Deadeye, was developed primarily for shore bombardment.  However, this program was cancelled in 1989.

3) Misfires are semi-automatically removed.

4) The Rocket Assisted Projectile (RAP) Mark 58 was developed during the 1960s.  The rocket motor burned for 34 seconds.

5) The illumination round burns for approximately 50 seconds.

6) Bourrelet diameter was 4.985 inches (12.66 cm).

USA:  Northampton (4), Mitscher (2), Forrest Sherman (3), Charles F. Adams (2), Farragut (1), Belknap (1), Truxton (1), Knox (1) and Forrestal (8):  Mark 42

Japan:  Tachikaze (2), Takatsuki (1), Shirane (2) and Haruna (2):  Mark 42

Spain:  Andalucia (1):  Mark 42

Other Mods:  N/A

1) The Mark 42 Gun Mount was produced in 10 different Mods.  Mods 1 through 6 were the first mounts to enter service and were used on USS Northampton (CLC-1) and DL-2 through DL-5.  The Forest Sherman (DD-931) class were originally equipped with Mods 7 and 8.  The Mod 8 mount had a radar system integrated into the mount which was never really successful.  The radars were removed at the first overhaul and the mounts reverted to a Mod 7 designation.  The Mod 9 mounts were first introduced on the Knox (FF-1052) class frigates and were a lighter design using all solid-state electronics.  Mod 9 was also exported to Spain.  Only two men were needed in the gunhouse in this Mod versus four for the Mod 7.  The Mod 7 had superior acceleration over the Mod 9, 60 degrees per second² for the Mod 7 versus 40 degrees per second² for the Mod 9.  The Mod 10 mounts were an upgrade of the Mod 7 mount that entered service in 1970's.

2) This mount is fed by two loader drums which each hold twenty rounds of ammunition.

3) Later mods were lighter and had lower manning requirements, falling from 20 men in the original Mod 0 to 13 in the Mod 9 and to 12 in the Mod 10 (gun captain and 11 crewmen).

4) This mounting operates from 440 Vac 60 Hz three phase.

5) This mounting consists of two component groups:  The lower structure (below deck) and the upper structure (above deck).  Lower structure components include parallel two-stage hoist/loader drum arrangements that deliver an uninterrupted flow of ammunition to the gun.  Upper structure components load the ammunition, aim the gun, fire the ammunition and eject the empty powder cases.  The lower structure was originally produced by the US Navy Naval Ordnance Station in Louisville, Kentucky.  The two ammunition loading systems in the lower component group feed the gun alternatively.  Each system has a cartridge drum and a projectile drum, with each drum holding twenty units of ammunition.  The drums usually rotate together, but the shell drum can rotate independently of the cartridge drum, which allows different ammunition to be selected during the loading cycle.  The projectile and cartridge are mated when they leave their respective drums and the complete round moves from the lower to the upper hoist and then to the upper hoist and finally to the a cradle which swung up to throw it into a transfer tray from which it is rammed into the breech.  The only manual element of this system is the placing of the cartridges and projectiles into the loading drums.

6) Forrest Sherman class destroyers modified into missile ships lost both of their aft 5"/54 (12.7 cm) guns.  Other members lost No. 2 gun and their 3"/50 (7.62 cm) guns in order to fit an ASROC launcher.  Northampton lost three of her 5"/54 (12.7 cm) guns by the time she was decommissioned in January 1970.  Forrestal class carriers lost their four forward 5"/54 (12.7 cm) guns in the early 1960s as it was found that their sponsons slowed the ship down in rough seas.  The after guns followed in the 1970s, with Ranger CVA-61 being the last active carrier to carry 5"/54 (12.7 cm) guns until her last pair was removed in 1977.