These guns were hand-loaded, but power-rammed, which gave them a high rate of fire and a capability of being easily loaded at any angle of elevation, both of which are highly desirable qualities for an anti-aircraft weapon. The introduction of proximity-fuzed AA shells in 1943 made this weapon an even more potent AAA gun.
The earliest mountings as used on USS Farragut (DD-348) were pedestal mounts with shell and cartridge hoists located on the deck behind the gun mount. However, starting with USS Gridley (DD-380), a new base-ring mounting with integral shell hoists on the axis of the mount was introduced. This type of mounting meant that shells and cartridges could be passed directly to the gun's breech at any angle of train, thus significantly improving the practical rate of fire. Most subsequent designs, including all twin mountings, were similar, although a simpler base ring mount lacking hoists was introduced in 1943 for use on auxiliary vessels.
There were some teething troubles when this gun was introduced in 1934, but a BuOrd report of 1945 states that during World War II they were considered to be highly reliable, robust and accurate, a reputation they retained even after the end of the war when the 5"/54 (12.7 cm) series of weapons were introduced. When coupled with the Mark 37 Fire Control System, used on most US warships built between 1939 and 1946, these guns were quite effective in the AA role. For example, during gunnery trials in 1941, USS North Carolina (BB-55) was able to repeatedly shoot down drone aircraft at altitudes of 12,000 to 13,000 feet (3,700 to 4,000 m), about double the range of the 5"/25 (12.7 cm) AA Mark 10 used on older ships.
These guns were introduced to the British Royal Navy in 1941-1942 when HMS Delhi was rebuilt in New York Navy Yard. The British were impressed with the combination of the 5" (12.7 cm) gun and Mark 37 Fire Control System and tried to purchase additional units, but the rapid ramping up of US warship construction prevented any diversion.
The Mark A prototype for this gun was created from a cut-down 5"/51 (12.7 cm) Mark 9, the only version of that weapon that used semi-fixed ammunition.
Mods 0 and 1 were of autofretted monobloc construction and used a semi-automatic vertical sliding wedge breech mechanism. The gun barrel was secured to the housing by a bayonet joint, thus allowing easy barrel replacement. Mod 2 used a non-expanded barrel of higher strength steel. Over 8,000 of these weapons were produced between 1934 and 1945, broken down as 2,168 guns in single mountings, 2,714 guns in twin mountings and 3,298 guns in single mountings for auxiliary ships. These figures may not include guns produced prior to 1 July 1940, at which time there were 315 single, 52 twin SP and eight twin DP mountings in the entire US Fleet. Average cost was $100,000 per gun assembly, which does not include the cost of the mounting. Millions of rounds of ammunition were produced for these guns, with over 720,000 rounds still remaining in Navy storage depots in the mid-1980s.
USS Atlanta CL-51 refueling in October
|Designation||5"/38 (12.7 cm) Mark 12|
|Ship Class Used On||1934 to 1948
First used on USS Farragut (DD-348)
Used on nearly all World War II-era new-construction warships destroyer-sized and larger along with many auxiliaries and smaller warships
Also used to rearm many older ships such as battleships and USS Saratoga (CV-3)
HMS Delhi was refitted with these guns
Post-World War II
USA: Brooke (FFG-1), Garcia (FF-1040), Long Beach (CGN-9), Albany (CG-10) and USCG Hamilton (WHEC-715) classes
Danish: Peder Skram class frigates
Italian: Impetuoso (D558) and San Giorgio (D562) classes
|Date Of Design||about 1932|
|Date In Service||1934|
|Gun Weight||3,990 lbs. (1,810 kg) without breech|
|Gun Length oa||223.8 in (5.683 m)|
|Bore Length||190 in (4.826 m)|
|Rifling Length||157.2 in (3.994 m)|
|Twist||Uniform RH 1 in 30|
|Chamber Volume||654 in3 (10.72 dm3)|
|Rate Of Fire||Pedestal and other mounts lacking integral
hoists: 12 - 15 rounds per minute
Base ring mounts with integral hoists: 15 - 22 rounds per minute
1) Barrel was chrome plated from the muzzle to include all rifling, the projectile band slope and the forward portion of the chamber. Total length of plating was 164.5 in (4.178 m) and was 0.00050 in (0.0127 mm) thick.
2) The guns installed on HMS Delhi had originally been destined for USS Edison DD-439.
|Projectile Types and Weights||AP - 54.0 lbs. (24.5 kg)
AAC Marks 31 and 35 - 55.18 lbs. (25.0 kg)
Common Mark 32 - 54.0 lbs. (24.5 kg)
Mark 33 Bombardment - 63.3 lbs. (28.7 kg)
AAVT Marks 35 and 49 - 54.61 lbs. (24.8 kg)
HC Marks 35 and 49 - 54.3 lbs. (24.6 kg)
Special Common Marks 38 and 46 - 55.18 lbs. (25.0 kg)
RAP Mark 57 - 54.3 lbs. (24.6 kg)
Illum Marks 27 and 45 - 54.39 lbs. (24.7 kg)
|Bursting Charge||AAC - 7.6 lbs. (3.4 kg)
AAVT - 7.9 lbs. (3.6 kg)
Common - 2 lbs. (0.9 kg)
HC - 7.6 lbs. (3.4 kg)
RAP - 3.5 lbs. (1.6 kg)
|Projectile Length||20.75 in (52.7 cm)|
|Propellant Charge||Flashless: 15.5 lbs. (7.031 kg)
Non-flashless: 15.4 lbs. (6.986 kg) NC
Empty cartridge case weighed 13.25 lbs. (6.01 kg)
|Muzzle Velocity||New gun: 2,600 fps (792 mps)
Average gun: 2,500 fps (762 mps)
|Working Pressure||18.0 tons/in2 (2,835 kg/cm2)|
|Approximate Barrel Life||4,600 rounds|
|Ammunition stowage per gun
(see Note 3)
|Yorktown (CV-6) and Essex (CV-9):
North Carolina (BB-55), South Dakota (BB-57) and Iowa (BB-61): 450 rounds
Cleveland (CL-55), Baltimore (CA-68), Alaska (CB-1): 500 rounds
Atlanta (CL-51): 450 rounds
Pre-war destroyers of the Farragut (DD-348) through Sims (DD-409) classes: 300 rounds
Benson (DD-421) and Gleaves (DD-423): 320 - 360 rounds
Fletcher (DD-445): 350 rounds (420 in later ships)
Allen M. Sumner (DD-692) and Gearing (DD-710): 360 rounds
1) Rounds were normally 5.25crh.
2) Some rounds may have been slightly boat-tailed.
3) Outfits listed are the design figures. Pre-war destroyers normally carried about 100 to 150 rounds per gun plus 100 illumination rounds per ship with the balance carried in magazines on Destroyer Tenders (AD). After 1940 outfits were increased to the numbers listed above plus about 200 illumination rounds per ship. As the war went on, ammunition stowage on new designs was increased where possible. Some examples: Late war Fletcher (DD-445) class carried 525 rounds per gun in magazines plus 50 ready rounds per gun. Late war A.M. Sumner (DD-692) class carried 422 rounds per gun in magazines plus 50 ready rounds per gun. The A.M. Sumner class also carried 292 illumination rounds per ship in magazines plus 48 ready illumination rounds per ship. However, the stowage for pre-war destroyers could not be so greatly increased. For example, the Farragut class USS Aylwin (DD-355) had about 250 rounds per gun in magazines plus 50 ready rounds per gun in 1944. The rebuilt USS Selfridge (DD-357), which had traded her eight SP guns for five DP guns after receiving torpedo damage in 1943, carried about 260 rounds per gun in magazines and 43 ready rounds per gun plus 85 illumination rounds per ship in 1944. Battleships carried 500 rounds per gun plus 40 special types per gun in magazines and 55 rounds ready rounds per gun. Ready rounds for all ships were stored in handling rooms usually located directly below each mount.
4) The cartridge cases were sealed with cork plugs which extended about 2.5 in (6.4 cm) past the mouth of the case.
5) AA Common rounds used both nose and base fuzes. The base fuze was an instantaneous contact type while the nose fuze was a adjustable time delay type.
6) Outfits for most ships during World War II were usually AA Common plus illumination. The Porter (DD-356) and Somers (DD-381) classes carried mostly Common as they were armed with SP guns, but they did carry a few AA Common rounds intended for use against torpedo bombers and other low-flying planes.
7) The Rocket Assisted Projectile (RAP) round was developed during the 1960s. The rocket engine burned for 40 seconds.
8) Projectiles leave the barrel rotating at about 208 RPS.
9) The illumination round burns for approximately 50 seconds.
55.18 lbs. (25.03 kg)
MV of 2,500 fps (762 mps)
53 lbs. (24.04 kg)
MV of 2,600 fps (792 mps)
1) At a new gun muzzle velocity of 2,600 fps (792 mps), the AAC Mark 49 had a maximum range of 18,200 yards (16,640 m).
2) This weapon had a maximum slant range of 12,000 yards (11,000 m).
3) RAP round had a maximum range of 23,770 yards (21,735 m).
4) Time of flight for AAC projectile with
MV = 2,500 fps (762 mps):
|4,000 yards (3,660 m)||
|5,400 yards (4,940 m)||
|7,400 yards (6,770 m)||
|11,000 yards (10,060 m)||
|13,800 yards (12,620 m)||
1) These figures are taken from USN armor penetration curves published in 1942.
2) It should be noted that US ships during World War II did not normally carry AP ammunition for these guns as the AA Common projectiles were considered to be more useful against a greater variety of targets.
|10,000 yards (9,140 m)||
1) Data from "Destroyer Weapons of World War 2."
2) As noted above, this projectile was carried by most ships instead of AP rounds.
(see Notes 1 and 23)
|Single Open or Open-back Pedestal Mounts
Farragut (5) and Mahan (5): Mark 21
Gridley (2), Dunlap (3) and Bagley (2): Mark 21 [stern mounts]
Wichita (4): Either Mark 21 or Mark 24
Yorktown (8) and Enterprise (8): Mark 21 Mod 16
Wasp (8): Mark 24 Mod 1
Hornet (8): Mark 24 Mod 2
Independence (2) and Essex (4): Mark 24 Mod 11
Single Enclosed Base Ring Mounts
Single Open Base Ring Mounts
Twin Enclosed Base Ring Mounts
(see Note 11)
|Single Open Pedestal Mounts
Mark 21: 29,260 lbs. (13,272 kg)
Mark 24: 31,200 lbs. (14,152 kg)
Single Open Base Ring Mounts
Single Enclosed Base Ring Mounts
Twin Enclosed Base Ring Mounts
(see Note 3)
All with the following exceptions: -15 / +85 degrees
Mark 24 Mod 11: -10 / +85 degrees
Mark 30 Mod 51: -5 / +85 degrees
Mark 30 Mod 80: -15 / +27 degrees
|Elevation Rate||Single Mounts
Mark 24: 15 degrees per second
Mark 25: 15 degrees per second
Mark 30: 15 degrees per second (GE controls)
Mark 30: 18 degrees per second (Ford controls)
Mark 37: 15 degrees per second
|Train||Destroyers: Depending upon position,
arc of 284 degrees up to an arc of 330 degrees
Cruisers and Capital ships: Bow and stern mounts: about -150 / +150 degrees
Cruisers and Capital ships: Broadside mounts: about -80 / +80 degrees
|Train Rate||Single Mounts
Mark 24: 28.75 degrees per second
Mark 25: 28.7 degrees per second
Mark 30: 28.75 degrees per second (GE controls)
Mark 30: 34 degrees per second (Ford controls)
Mark 37: 30 degrees per second
(see Note 10)
|All mounts except Mark 22: 15 in
Mark 22: 19 in (48 cm)
1) The mounting types, designations and quantities shown in this table are primarily for warships "as commissioned" and are mainly the result of my research for a Technical Board essay on USN naval gun mounting production during World War II. These figures may not be in agreement with many published works, but I believe them to be correct. Besides those ships listed above, this gun was extensively used on auxiliaries and merchant ships.
2) The Mark 21 pedestal mounts were at the limit of turning masses that could be easily manhandled. To get to this weight, BuOrd sacrificed shields and ammunition hoists and accepted the resulting lower rate of fire. These guns were fed from deck mounted scuttles, from which rounds could be passed to a rack of fuze-setters on the rotating mount. Bow mounts on destroyers had simple open-back shields while stern mounts were left open. The shields for these mounts were notable for having a bulge on the left side to accommodate the fuze-setter rack. All Mark 21 mountings were originally manually trained and elevated, but RPC was added during the war to most ships with 1.5 hp elevating and 2 hp training motors.
3) The Mark 22 twin mount used on the Porter (DD-356) and Somers (DD-381) destroyer classes was the only SP mounting ever developed for these weapons. Their low maximum elevation of +35 degrees of elevation was adopted mainly as a weight savings, as it was calculated that these ships would only be able to carry six DP guns rather than the eight SP guns that they actually did carry. This mounting used a 15 hp training motor and a 5 hp elevating motor. Most of these destroyers lost their mount No. 3 as weight compensation for growth in other areas and those destroyers modernized during World War II had all of their SP mountings replaced with two twin and one single DP mountings. Almost all other mounting types allowed +85 degrees of positive elevation, with the exception of those altered for specific applications, such as the Mark 30 Mod 80, which was installed on escort carriers under the flight deck overhang. Most single mountings had a maximum negative elevation of -15 degrees, but a few were restricted to -7 or -10 degrees for application reasons.
4) The Mark 24 series were improved pedestal mounts that had RPC as designed and were powered by a single 5 or 10 hp motor which worked both elevation and train along with a 5 or 7.5 hp motor for ramming. Hoists were in the fixed structure for these mountings. These mountings were considered to be near the maximum weight possible that would still allow them to be hand worked in an emergency. Many of these mountings had the familiar fuze-setter racks on the platform, controlled by their Mark 33 and Mark 37 Fire Control Systems (FCS).
5) The Mark 25 was the prototype enclosed base ring mounting. As best as I have been able to determine, these were only used for the bow mounts on the four destroyers of the Gridley (DD-380) class and for the bow mounts on USS Dunlap (DD-384) and USS Fanning (DD-385). As such, these last two ships formed a sub-class within the Mahan (DD-364) class, as all other ships of the Mahan class used Mark 21 pedestal mounts in all positions. Some of these Mark 25 mounts appear to have been replaced with Mark 30 enclosed base ring mounts during the war.
6) The Mark 30 enclosed base ring mounts were first introduced on USS Wichita (CA-45). The Mark 30 mountings made up by far the majority of single mountings built during the war. The Mark 30 ran up to Mod 86, with Mod 0 being the original enclosed mounting and Mod 1 being the original open mounting. There were also semi-enclosed mounts which had the upper half of the shield removed with a canvas cover to protect the interior of the mount. Many of the Mark 30 modifications were trivial in nature. For example, USS Fletcher (DD-445) used Mod 16 in positions 1 and 5, Mod 19 in position 2, Mod 30 in position 3 and Mod 31 in position 4. The differences were mainly related to the elevation and training limitations inherent in the different mounting positions. Escort Carriers (CVE) completed during the war used Mark 30 Mod 80 which was a simplified base ring mounting which lacked shields, axial hoists and RPC. The single open Mark 30 Mod 48 and Mark 30 Mod 51 mountings were simplified base-ring types for auxiliaries and merchant ships and lacked integral shell hoists.
7) Almost all Mark 25 and Mark 30 base ring single mounts had an integral shell hoist on the axis of the mounting which allowed shells to be passed directly to the gun at any angle of train. Fuzes were automatically set as the shells traveled up the hoist. Cartridges were passed up to the gun through a scuttle also on the rotating mass. These base ring mounts with integral shell hoists and cartridge scuttles had the advantage that projectiles and cartridges were presented to the loaders at exactly the same position and orientation regardless of the mount's elevation or training and thus simplified and sped up the loading procedure. Both the shell hoist and the cartridge scuttle were on the left side of the mount. Mark 25 and enclosed Mark 30 base ring mountings used a single 10 hp motor to work both elevation and train, a 7.5 hp motor for the hoists and a 7.5 hp or 5 hp motor for ramming.
8) Destroyers of the Gridley (DD-380), Dunlap (DD-384) and Bagley (DD-386) classes had something of a mixed battery, as they had enclosed base ring mountings on the bow, but open pedestal mountings on the stern. USS Benham (DD-397) was the first destroyer with a uniform battery of base ring single mountings, although the stern mounts were still of the open type. It was not until the larger Fletcher (DD-445) class that destroyers had all five guns in enclosed mountings.
9) All twin mounts were base ring types and were generally similar to single enclosed base ring mounts. Twin mounts differed from single mounts in that there were twin powder hoists for the cartridges as well as twin shell hoists. The hoists for the right gun came up through the deck on the left side of the gun while those for the left gun came up on the right side. Twin mounts took about 27 crewmen in the mount itself and in the upper handling room. Additional personnel were required in the lower handling room during sustained firing periods.
10) The maximum, metal to metal recoil distance for most mountings was 19 inches (48 cm).
11) The major differences in weight for enclosed mountings was from the thickness of the shield, which ran from 0.25" (0.64 cm) for destroyer mountings up to 2.5" (6.4 cm) on battleships.
12) Ramming was power-worked on all mountings and was either pneumatic or by a 5 hp electric motor with hydraulic drive. This allowed any-angle loading and thus a high rate of fire even at high elevations. In an emergency, ramming could be performed manually.
13) Most of the five-gun destroyers built prior to 1942 had one mounting removed during the war as weight compensation for growth in other areas, such as ASW equipment, light AA and electronic installations. Some four-gun destroyers lost one or both gun shields on the stern mountings as weight compensation. The Sims (DD-409), Benson (DD-421) and Gleaves (DD-423) classes started out with three enclosed mountings (mounts 1, 2 and 5) and two open mountings (mounts 3 and 4). After experience with an Atlantic winter in 1941-42, the open mounts were replaced with open-top, semi-enclosed mounts with a canvas cover for weather protection. Later, mount 3 was removed entirely from these ships. During her refit in the summer of 1945, USS Shaw (DD-373) was found to be significantly overweight, probably because of the structural strengthening performed during her reconstruction in 1942 following major damage received during the Pearl Harbor attack. As a result, she was reduced to three 5" (12.7 cm) guns to allow for additional light AA guns. All of her torpedo tubes were also removed during this refit.
14) Some destroyer escorts had the back of the shield of their bow mounting cut off at an angle to allow for Hedgehogs firing directly ahead.
15) USS Savannah (CL-42) had her 5"/25 (12.7 cm) guns replaced with 5"/38 (12.7 cm) guns in 1944.
16) Many older ships were rearmed with these guns during the war. For example, in 1942 USS Saratoga (CV-3) was rearmed with four 5"/38 (12.7 cm) Mark 32 Mod 2 twin mountings and eight 5"/38 (12.7 cm) Mark 30 Mod 33 single mountings.
17) All twin DP mountings were equipped with RPC gear and powered by electric motors through hydraulic gear. Training was by a 4 hp motor while the guns were elevated by a 7.5 or 10 hp motor. Each gun had a 7.5 or 10 hp motor for the hoists and a 5 or 7 hp motor for the rammer.
18) USS Yorktown (CV-5) and Enterprise (CV-6) were originally designed with eight Mark 21 Mod 1 pedestal mounts. During construction, it became apparent that there was not enough clearance around the deck edge for this Mod. For that reason, the mounts were redesigned to have a lower loader's platform and then designated as Mark 21 Mod 16. Yorktown was sunk with these mounts, but Enterprise had hers replaced with Mark 24 Mod 11 mounts during her overhaul at Puget Sound in 1943. Sister-ship Hornet (CV-8) was completed with eight Mark 24 Mod 2 mounts.
19) Most USS Essex (CV-9) class carriers were completed with four Mark 32 twin mounts, mainly Mods 0, 2 and 4, and four Mark 24 Mod 11 pedestal single mounts. Post-war, a few of these ships had their pedestal mounts replaced with Mark 30 base ring mountings for reasons that are not clear. By the mid-1960s, all of the twin mountings were removed from those carriers still in commission. A few of these carriers were modified such that they now carried eight single mountings, two on each corner.
20) USS Independence (CVL-22) was completed with two Mark 24 Mod 11 mounts, but these were removed soon after commissioning at the CO's request. No other carrier of this class was commissioned with these guns.
21) The Mark 37 was a much simplified mounting developed by Northern Ordnance, Inc. that was primarily intended for merchant ships and auxiliaries. This mounting had a simplified sighting system as it was designed to be used only in local control. Over 3,600 were built during the war, with about 1,600 of these being used on merchant ships.
22) The Mark 22 SP twin mounting had the gun axes 72 inches (183 cm) apart. All DP twin mountings had the gun axes 84 inches (213 cm) apart.
23) According to Danish Naval History, these guns when used on the Peder Skram class frigates were designated as 127 mm Gun K M/60 LvSa2. These ships each had one of their Mark 38 mountings removed to fit Harpoon Launchers during the 1980s.
24) USCG Hamilton (WHEC-715) was rebuilt starting in 1985 and had her 5"/38 (12.7 cm) gun replaced with a 76 mm (3") Mark 75.
Operating Instructions for Five Inch, 38 Caliber, Gun Crews on the HNSA Website