5"/32 Cal. Gun

   Installed in the 175 Fletcher Class Destroyers as well as the GARCIA class destroyer escorts, Coast Guard Cutters and countless U.S. Naval auxiliary ships, the widespread MK 30 gun mount, as seen at left on RADFORD, with its single MK 12 Mod 1 barrel was originally designed for destroyer installations in the mid 1930's and was the early destroyer surface weapon of World War II. 

The enclosed single mount had a base-ring type mounting that allowed the gun to turn within its 11' 11" circle. On top of the mounting was the gun house itself built upon the carriage assembly that connected to the ring via the rotating assembly. With the ammunition handling room below it, the combined gun mount weighed 41,000 lbs. 
     As the basic performance per gun of the MK 30 gun mount is the same for the twin mount, as it fired the same 55 pound projectile, please see the below specifications for the MK 38 gun mount.

   Installed on the SUMNER and GEARING Class series of Destroyers, the TWIN 5 inch/38 Caliber Gun installed in the MK 38 mount was designed specifically for Destroyer installations. With its base ring and enclosed mounting, it became the most successful and widely used gun mounting in the U.S. Navy  and was not only installed on the SUMNER and GEARING class destroyers, but Auxiliaries Vessels as well, during World War II.

   With each of the two 5 inch MK 12 Mod 1 guns equipped with a semi-automatic dual-purpose mounting with separate ammunition and cartridge hoists for each gun, The MK 38 mount has the ability to be operated by a remote fire control director. However, including the loaders below deck, the gun mount crew included some 26 personnel; 13 on the mount itself! 
     Adding 4 different thicknesses for gun shields - the MKs 41, 48, 53 and 62 (see below under specs), the amount of splinter protection could be varied with weights from 14,500 to 24,400 lbs.

   The rate of fire for the MK 38 mount was typically 15 rounds per barrel per minute. However, a really good gun crew could achieve 22 round per barrel per minute, however at that rate problems developed.

   According to a Gunner's Mate (GM1) on the USS George K. Mac Kenzie (DD-836) they set a record when they fired 151 rounds in five minutes from their 5 inch/38 caliber MK 38 twin mount but then had to cool the barrels off with the ship's fire hose. This was in preparation for a Marine landing on a small peninsula not far from Da Nang. The Marine spotter in his small Piper aircraft called the landing off. He said there was not a tree left standing and nothing left to hide the enemy! 

    Further, the barrel of the 5 inch/38 caliber gun did wear out with this type of use. While specifications called for a barrel service life of 4600 rounds, using basic rounds the tube life expectancy on-ship was about 1,500 rounds but as muzzle velocity increased, a drop of about 800 rounds was to be expected in tube life. Replacing these gun barrels on the FRAM destroyer was not an easy thing: The method involved a special wrench which attached at the base of the barrel, and a 20 LB sledge hammer.  The barrel - unscrewed- seen left and took approximately 8 hrs per gun vs. the 1 hr for the 5 inch/54 cal MK 42 gun. Disassembled from the turret, the barrel weighed some 3,991 lbs. This was the process for the forward mounts. For the Aft 5" mount at the fantail (Mount 53), the complete gun mount was completely taken off the ship and taken to the overhaul shop.  A month later it was brought back and it was like brand new.

  It should be noted that during the Vietnam War, a 5 inch/38 rocket-assisted projectile was developed for greater surface range. This became the MK 57 round and was 51.5" long and had a range of 23,770 yards. The MK 57 had a rocket that burned for 40 seconds with a shell that carried 3.5 lbs of explosives. This corresponds to the standard 5" round, the MK 66 which were 50.14" long, had a range of 14,000 yards and carried a shell with 7.9 lbs of explosives.

Basic Data - 5 inch/38 Cal MK 38 Gun Mount

Caliber: 5 inch (127 mm)
Length of barrel: 38 calibers
Elevation: -15 to +85 degrees
Traverse: 328.5 degrees
Projectile Weight: 55 lbs
Muzzle velocity: 2500 feet/second
Recoil: 15 inchesGUN SHIELD Thickness Data:
Gun Mount Assembly weight: 
With MK-48 Shield: 95,700 Pounds
With MK-53 Shield: 105,600 Pounds

GUN SHIELD Thickness Data:
MK-41 = 1/4" Thick
MK-48 = 1/2" Thick
MK-53 = 1/8" Thick