5"/38 caliber gun
name= 5"/38 Caliber Gun
caption= Two Mk 30 single enclosed base ring mounts on a "Fletcher" class destroyer.
origin= United States
type= Deck Gun
used_by= US Navy, US Coast Guard, Royal Navy, Danish Navy, Italian Navy, Japanese Navy, South Vietnamese Navy, and every navy that bought surplus WWII, U.S. Navy warships
wars= World War II, Korea, Vietnam, First Gulf, Falklands, and wars that involved navies who bought surplus WWII, U.S. Navy warships
weight= Mk 12 Gun Assembly: convert|3990|lb|kg|abbr=on. Mounts varied from convert|29260|lb|kg|abbr=on to convert|170653|lb|kg|abbr=on
length= Mk 12 Gun Assembly: 223.8 in (5.685 m)
part_length= 190 inch bore (4.83 m), 157.2 inch (4.00 m) rifling
crew= Varied on mount type
cartridge= 5 inch (127 mm)
rate= Design: 15 rpm
velocity= convert|2600|ft/s|m/s|abbr=on new; convert|2500|ft/s|m/s|abbr=on average
sights= Optical telescope
breech= Vertical sliding wedge
recoil= 15 inches (38 cm)
elevation= −15° to +85°
traverse= 328.5 degrees
The Mark 12 5"/38 caliber gun is a US naval gun.
The gun is installed into Single Purpose [ cite web |url=http://www.navweaps.com/Weapons/WNUS_5-38_mk12.htm |title=United States of America 5"/38 (12.7 cm) Mark 12 |accessdate=2007-08-30 |year=2006 |month=November |author=DiGiulian, Tony |publisher = navweaps.com|quote=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.] and Dual Purpose mounts used primarily by the U.S. Navy. On these 5" mounts, Single Purpose (SP) means that the mount is limited to 35° elevation, [ cite web |url=http://www.navweaps.com/Weapons/WNUS_5-38_mk12.htm |title=United States of America 5"/38 (12.7 cm) Mark 12 |accessdate=2007-08-30 |year=2006 |month=November |author=DiGiulian, Tony |publisher = navweaps.com|quote= Mark 22: −10 / +35 degrees] and is designed to fire at surface targets only, while Dual Purpose (DP) means that it is designed to be effective against both surface and aircraft targets because it can elevate to 85°. The 38 caliber barrel was a mid-length compromise between the previous United States standard 5"/51 low-angle gun and 5"/25 anti-aircraft gun.
Among naval historians, the 5"/38 gun is considered the best intermediate-caliber [a Bore diameter greater than 4 inch (102 mm) and less than 8 inch (203 mm)] , dual purpose naval gun of World War II . The comparatively high rate of fire for a gun of its calibre earned it an enviable reputation, particularly as an antiaircraft weapon, in which role it was commonly employed by
United States Navyvessels. Base ring mounts with integral hoists had a nominal rate of fire of 15 rounds per minute per barrel; however, with a well-trained crew, 22 rounds per minute per barrel was possible for short periods. cite book |title =NAVAL ORDNANCE AND GUNNERY, VOLUME 1, NAVAL ORDNANCE, NAVPERS 10797-A|publisher =U.S. Navy, Bureau of Naval Personnel|date =1957 edition|location =Washington 25, D.C.] On pedestal and other mounts lacking integral hoists, 12 to 15 rounds per minute was the rate of fire. [ cite web |url=http://www.navweaps.com/Weapons/WNUS_5-38_mk12.htm |title=United States of America 5"/38 (127 mm) Mark 12 |accessdate=2007-08-30 |year=2006 |month=November |author=DiGiulian, Tony |publisher = navweaps.com|quote=Pedestal and other mounts lacking integral hoists: 12 - 15 rounds per minute]
The 5"/38 cal gun was mounted on a very large number of U.S. Navy ships in the
World War IIera. It has disappeared from active U.S. Navy service, but it is still on mothballed ships of the United States Navy reserve fleets. It is also used by a number of nations who bought or were given U.S. Navy surplus ships. 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 because of the large number of Reserve Fleet ships with 5"/38 cal guns on board.
Mark 12 5"/38 cal gun assembly
Each mount carries one or two Mk 12 5"/38cal Gun Assemblies. The gun assembly shown is used in single mounts, and it is the right gun in twin mounts. It is loaded from the left side. The left gun in twin mounts is the mirror image of the right gun, and it is loaded from the right side. The Mk12 gun assembly weighs convert|3990|lb|kg|abbr=on. cite web |url=http://www.navweaps.com/Weapons/WNUS_5-38_mk12.htm |title=United States of America 5"/38 (127 mm) Mark 12 |accessdate=2007-03-11 |year=2006 |month=November |author=DiGiulian, Tony |publisher = navweaps.com] The Mark 12 Gun Assembly was introduced in 1934, where it was first used in single pedestal mounts on the "Farragut" class destroyers, [ cite web |url=http://www.navweaps.com/Weapons/WNUS_5-38_mk12.htm |title=United States of America 5"/38 (12.7 cm) Mark 12 |accessdate=2007-08-30 |year=2006 |month=November |author=DiGiulian, Tony |publisher = navweaps.com|quote=The earliest mountings as [sic] used on USS Farragut (DD-348) were pedestal mounts with shell and cartridge hoists located on the deck behind the gun mount.] but by the time of World War II they had been installed in single and twin mounts on nearly every major warship and auxiliary in the US fleet.
The major Mk12 Gun Assembly characteristics are:;Semi-Automatic : Some of the recoil energy is use to prepare to gun for the next round. The firing pin is cocked, the breech is opened, the spent powder case is ejected from the chamber, and a compressed air valve is temporarily opened to expel residue from the previous round out the muzzle.;Hand Loaded : A Projectile-man and a Powder-man is stationed at each gun assembly. Their job is to move the round consisting of a projectile and a powder case from the hoists or racks to the rammer tray, then start the ram cycle.;Power Rammed : An electric-hydraulic rammer is bolted to the top of the slide. This convert|5|hp|abbr=on to convert|7.5|hp|abbr=on system is designed to ram an convert|93|lb|kg|abbr=on, 47.5 inch (1.2 m) long round into the chamber at any gun elevation in less than a second.;Vertical Sliding-wedge Breech Block (See drawing): The breech block closes the chamber behind the powder case. It also holds the firing pin assembly.;Hydraulic Recoil : Two hydraulic pistons in the housing absorb the major shock of recoil. They also buffer the end of counter-recoil for a soft return to battery.;Pneumatic Counter-Recoil : A chamber in the housing is filled with high pressure air. Sticking out the back of this chamber is a piston. This piston pushes against to rear of the slide to return the housing back into battery (all the way forward; ready to fire). When the gun is in battery, the pressure in this chamber is about convert|1500|psi|MPa|abbr=on. During recoil, the pressure rises to about convert|2200|psi|MPa|abbr=on. ;Barrel : The barrel of a 5"/38
calibergun has a five inch (127 mm) bore and a length 38 times the bore diameter, or convert|190|in|m long. It has chrome plated rifling with 45 grooves that have a uniform right hand twist. There is one full revolution of the twist in convert|150|in|mm. The initial velocity of a new gun is convert|2600|ft/s|m/s|abbr=on. It is connected to the housing with a bayonet joint that allowed for replacement by destroyer tenders in the theater of operation. ;Ballistics : Maximum horizontal range, with a 55 pound projectile, is convert|18000|yd|km. In the antiaircraft role, it had a ceiling of 37,200 feet (11,300 m) at 85 degrees elevation.cite web |url=http://www.navweaps.com|title=Navy Weapons|accessdate=2007-08-19]
Loading and Firing
At the "load" command, the powder-man slips a primer protector off the end of the powder case, extracts the case from the scuttle or rack, and lifts it into the gun's rammer tray. Meanwhile, the projectile-man pulls a projectile out of the hoist or fuze setter, places it in the rammer tray in front of the powder case, and then pulls down on the rammer lever. This causes the power rammer to ram the projectile and powder case into the chamber. As the powder case clears the top of the breech block, the block rises to seal the chamber. The gun is then ready to fire. The case combination primer in the base of the powder case can be fired either electrically or by percussion. When the gun fires, the recoil’s rearward motion returns the rammer lever to the up position, and the rammer drives back to the rear of the rammer tray. During counter-recoil, the breech block is automatically lowered and the spent powder case is ejected from the chamber. When the gun has returned to battery, a blast of compressed air is sent down the bore to clean it out and the gun is ready to be reloaded.
There are four basic mount types: ;Twin : All twin mounts were enclosed, sat on a base ring stand, and had an ammunition-handling room, called the Upper Handling Room, below the mount. This type of mount was the standard installation on battleships, cruisers, early Destroyer Leader classes (these mounts on the DL's were single-purpose/anti-surface ship only), and later destroyers. It was also used on the island (starboard) side of the "Essex" class aircraft carriers. ;Enclosed Single : All enclosed single mounts sat on a base ring stand, and had an upper handling room. The enclosed single mount was used on some early destroyer classes, but by the end of World War II, it was mainly found on the many minecraft and auxiliaries which were developed from the older classes of destroyers, as well as on most of the destroyer escorts, and many large auxiliaries (repair ships, destroyer tenders, etc.). ;Open Single Base Ring Mount : This mount had an upper handling room. It was specially developed for installation in the walkways on the port side of aircraft carriers. It is also occasionally found on auxiliary vessels. ;Open Single Pedestal Mount : This was the first 5"/38cal type installed. It was put on the "Farragut" class destroyer in 1934. Some of these mounts placed on ship's forecastles were partially enclosed to protect the crew against bow spray, but they were still considered an open mount. Since these mounts did not have Upper Handling Rooms, they could be installed on ships without extensive reconstruction. For that reason, they were frequently used on armed merchant ships. There are several models of the 5"/38, differentiated by the word "Mark" (or its abbreviation "MK") and a number. Variations to the basic design are called "Modifications" (or its abbreviation "Mod"). For instance, 5"/38 MK 21 is a single-barrel open pedestal mount widely used on amphibious ships, auxiliaries, and merchant ships. The 5"/38 MK 30 is a single enclosed base ring mount widely used on
Destroyer escorts. The 5"/38 MK 38 is a twin mount specifically designed for newer destroyers.
;Base Ring Mounts : The ready service ammunition is kept in the upper handling room just below the mount. The projectile travels up to the gun room (also called the gun house) through an electric-hydraulic hoist. It arrives next the projectile-man; nose down and waist high. If the projectile has a time fuze, the fuze is automatically set as it goes up the hoist, and the hoist maintains the ordered fuze setting from the fire control system as long as the projectile stays in the hoist. The powder case is sent up through a powder scuttle in the gun room's deck just next to the powder man's feet. The men in the upper handling room hand carry the projectiles and powder cases from the ready service racks to the lower ends of the hoists while avoiding the equipment hanging down from the rotating mount. In a twin mount executing "Rapid continuous fire" (The firing keys are held closed, and the gun fires as soon as the breech closes.), they moved 30 to 44 projectiles and 30 to 44 powder cases per minute.
;Pedestal Mounts : The ready service ammunition is kept in lockers or compartments arrayed around the mount. The projectiles and powder cases are hand carried from ready service to the left side of the moving mount. The projectile is placed nose down in one of three Fuze Setter Mechanisms (commonly called fuze pots) on the mount. If the man is delivering a projectile with a mechanical time fuze, he then spins a hand crank just in front of that fuze setter mechanism. This would dial in the ordered fuze time into that projectile. The powder case is placed in a rack bolted to the mount's deck just behind the powder-man's feet.
Depending on the mount, a 5"/38 caliber gun could have a crew of from 15 to 27 personnel in the gun room and upper handling room. [cite book|title =NAVAL ORDNANCE AND GUNNERY, VOLUME 1, NAVAL ORDNANCE, NAVPERS 10797-A|publisher =U.S. Navy, Bureau of Naval Personnel|date =1957 edition|location =Washington 25, D.C.|quote=Approximately 27 men are required to man all stations in the mount and the upper handling room.] This does not include the personnel needed in the magazines during extended actions. There were two modes of mount operation that the crew was trained and expected to know. The primary mode was Automatic Control, where the mount was slaved to the Fire Control System. But if the Fire Control System was damaged, or if the ship's power was out; the mount could continue the action in Local Control. In US service, most gun crews were US Navy personnel. Even the civilian
Merchant Marineships had a small detachment of the Navy Armed Guard on board to operate the 5"/38 and other guns. One exception to this was on ships with a Marine Detachment, where the Marines manned one of the mounts, usually decorated with the Marine emblem. ("See the USMC emblem on the USS New Jersey's Mk 28, Mod 2 mount picture above.") ; Mount Captain : A senior Petty Officer or Gunnery Sergeant who was in command of the mount. In enclosed mounts, he stood on a platform that was located half way up the back bulkhead of the enclosure. There was a hatch on the top of the enclosure where he could stick his head and shoulders out the mount's top. On some mounts, this hatch had a steel hood welded around the back and sides ("See an example of this hood in the USS New Jersey picture.") This hood protected the Mount Captain from the muzzle blasts of adjacent weapons. He was wearing a sound powered telephone so that he could receive action orders from the battery commander, and send mount status reports back. Covering the telephone headset, there is a helmet specially designed to fit over the phone. Around his neck, he has a pair of gunnery binoculars which had a reticle scaled in angular mils. By ducking his head down into the mount, he could see the entire interior of the mount from his perch. Next to him was a voice tube down to the upper handling room. At arms length, he had switches for controlling communication, emergency lighting, and battle lanterns.cite web |url=http://www.navweaps.com/Weapons/WNUS_5-38_mk12_Crews.htm|title=How the 5"/38 crews operated|accessdate=2007-08-28] His duties during Automatic Control was to receive action orders from the battery commander (e.g.: "Mount 51, plot. Surface action starboard. Bearing 060. Slow salvo."), give the appropriate orders to his Gun Room and Upper Handling Room crews (e.g.: "Match pointers. Switch to automatic. Handling room fill the hoists with able able common and full service charge. Standby for slow salvo."), verify that his orders were being followed, and report his gun's status back to the battery commander (e.g: "Plot, mount 51 in auto."). In Local Control, he aims and fires his mount's gun(s) − sometimes without external help. With his gunnery binoculars, he estimates the range to the target, and its bearing rate. He then mentally converts these into range and deflection orders to his Sight Setter. After firing, he observes the fall of his shot, and makes sight corrections to his Sight Setter if necessary.
; Gun Captain : The Gunner's Mate(s) responsible for maintaining the mount. Daily, he goes through a ritual of checking fluid levels, lubricating bearings, cleaning gun sights, cycling powered equipment, testing firing systems, checking gas pressures, and verifying that all things needed in an action is present in his mount. In twin mounts, there will be a Gun Captain assigned to each gun assembly. The Gun Captain usually stands on his foot high tool box welded to the mount's deck, and offset from the gun's centerline. ("See the man in black standing on the box in the MK21 open mount picture.") This places him high and aft of the rammer motor. From there, he can watch the actions of the powder-man, projectile-man, breech block, and rammer. He can verify that the gun returns to battery before the next round is loaded. If something goes wrong, he is free to move around his gun to fix the problem. He knows everybody's job, and can step in if necessary. He knows what to do to return the gun to action after some failure. At the Mount Captain's command, he manually opens the breech block before the first round is loaded, and reports if the bore is clear. His duties are the same in Automatic or Local control.
; Pointer : . He changes the elevation of the gun, by moving his hand wheels, until the dial difference is zero. His dials are now "matched", and he switches the elevation drive into Auto. This disengages his hand wheels, and gives elevation control to the Fire Control System. Then, he moves the Electrical Fire Select Switch to "AUTO", and reports back to the Mount Captain, "Elevation in auto." He may now look through his sight, and if the Sight Setter has matched the sight-setter dial pointers, he will see the target in the cross-hairs. When the Mount Captain commands, "Switch to Local", he switches the elevation drive and the Electrical Fire Select Switch to local. In local control, he controls the gun's elevation with his hand wheels to keep his sight's horizontal cross hair on the target. At the the command of the Mount Captain, he fires the gun by squeezing the firing key on his right hand wheel.
; Trainer : . When the Mount Captain commands, "Match pointers. Switch to Automatic.", he looks down at the dials on his Indicator-Regulator. The dials also tell him the difference between the gun's present train angle and the ordered train angle. He changes the bearing of the gun, by moving his hand wheels, until the dial difference is zero. His dials are now "matched", and he switches the train drive into Auto. This disengages his hand wheels, and gives train angle control to the Fire Control System. Then, he reports back to the Mount Captain, "Train in auto." He may now look through his sight, and if the Sight Setter has matched the sight-setter dial pointers, he will see the target in the cross-hairs. When the Mount Captain commands, "Switch to Local", he switches the train drive to local. In local control, he controls the gun's train angle with his hand wheels to keep his sight's vertical cross hair on the target.
; Sight Setter : . cite book|title=GUNNER'S MATE 3, VOL. 1, NAVPERS 10158-A|publisher=UNITED STATES GOVERNMENT PRINTING OFFICE|date= 1952 edition|location=WASHINGTON, D.C.|pages=p.66] This is called matching the pointers, and it allows the sights to remain on the target while the mount is controlled by the Fire Control System. In local control, he takes sighting orders from the Mount Captain in yards of range and mils of deflection.
; Fuze Setter : . In Local Control, he follows the Mount Captain's fuze orders by spinning the hand crank until the dials in the window read the correct fuze time.
; Powder-man : Moves the powder case from the powder scuttle at his feet to the gun's rammer tray.
; Projectile-man : Moves the projectile from the hoist to the rammer tray, and then he pulls the rammer lever to load the round into the chamber.
; Hot Case Man : When the gun fires, he catches the ejected powder case and throws it out of the mount.
; Check Sight : He verifies that the mount is aiming at the target.
The Projectile has three major parts: the body, the fuze, and the explosive charge.
;Projectile BodyThe body is basically a machined steel tube with a pointed end. Around the tube near the base is a copper alloy ring called the rotating band. This band has a diameter larger than the bore, and when the projectile and powder case are rammed into the chamber, the band is jammed into the grooves of the bore's rifling. It forms a gas seal between the projectile and the bore. Also, as the projectile travels down the barrel, the rotating band grips the rifling to impart spin to the projectile.
;FuzeThe fuze detonates the projectile to cause maximum damage to the target. Different targets required different fuzes. The most important requirement of a fuze is that it remains unarmed until the projectile is well clear of the gun's muzzle on the firing ship. To do this, the fuze remains unarmed until a series of events take place. The first event is the shock of firing. The 5"/38cal projectile experiences at least a 14,000g acceleration as it is pushed down the barrel. This acceleration cause parts of the fuze to setback due to their inertia, and they shear pins that hold them in the unarmed position. The second event is the spinning of the projectile due to the bore's rifling. The 5"/38cal projectile spins at more than 200 revolutions per second when traveling at convert|2600|ft|m per second (New gun initial velocity). The centrifugal force of this spin causes other parts to move outward. The third event is the projectile's deceleration after it leaves the muzzle, and other parts creep forward. All of these events must take place in the correct order to arm the fuze.
List of fuze types:;Mechanical Time Fuze :A nose time fuze that detonates the shell after an adjustable time interval has elapsed since firing. ;Base Detonating Fuze :A base impact fuze screwed into the rear of a projectile to protect the fuze during impact. It delays the shell's detonation about 25 mSec after impact. This delay allows the projectile to get inside the target before exploding.;Point Detonating Fuze"':A nose impact fuze. Very fast detonation on the surface of the target.;VT fuze:also called a
proximity fuze, a nose electronic fuze that does not require impact to trigger. Designed to detonate close to the target. It was originally intended to be used against air targets. Now it is also used in shore bombardment and surface actions against fast boats. This is because the VT fuze has proved well suited for bursting the shell at the correct distance above the ground or water for maximum damage to lightly armored targets over a large area.
The powder case is a brass or steel alloy cylinder closed at one end. ("pictured above with the projectiles") It holds the propelling charge and a case combination primer. The charge is held packed around the primer by a wad, extender piece, and plug. [cite book |title =NAVAL ORDNANCE AND GUNNERY, VOLUME 1, NAVAL ORDNANCE, NAVPERS 10797-A|publisher =U.S. Navy, Bureau of Naval Personnel|date =1957 edition|location =Washington 25, D.C.|quote=In 40 mm and larger guns, a cardboard disc, or wad, is forced into the case and a distance piece, if one is needed, placed on top.] There are three types of powder cases:
:Full Service Charge::A 26.7 inch (679 mm) long, 12.3 pound (5.6 kg) brass case with 15.5 pounds (7.0 kg) of smokeless or flashless (used at night) powder. Used in surface and anti-aircraft actions.:Reduced Charge::A standard length case with less powder. This charge propels the projectile at a lower initial velocity. It is used in shore bombardment to lob shells, like a mortar, over obstacles to hit targets on the opposite side, and for propelling star shells at a lower velocity to protect the parachute from being shredded while it is deployed.:Clearing Charge::The Clearing Charge (also called, "The Short Round") is a short case, cut off and plugged just above the wad, with a full charge. It is used to clear the gun after a misfire. This case is essential for the safety of the mount, and it is kept in a special container in the mount whenever the ship is in a combat zone. A misfire is especially dangerous in semi-fixed guns. When the breech is opened after the misfire, the faulty powder case can be extracted, but the projectile remains jammed in the rifling. The clearing charge is removed from its container and is hand rammed into the chamber behind the projectile. With the clearing charge sealed in the chamber, the projectile is fired out the muzzle. It is important to clear the projectile out the muzzle. It is not easy or safe to back the projectile out the chamber with a bore rod pushed down the barrel from the muzzle. [cite book |title =NAVAL ORDNANCE AND GUNNERY, VOLUME 1, NAVAL ORDNANCE, NAVPERS 10797-A|publisher =U.S. Navy, Bureau of Naval Personnel|date =1957 edition|location =Washington 25, D.C.|quote=Whether a gun is hot or cold, the risks attendant upon removing a loaded and fuzed projectile seated in the bore, by backing out, are considered unwarranted...] Also, if the gun has fired a number of rounds just prior to the misfire, time is critical because the barrel may be hot enough to cook off the high explosive in the projectile. [cite book |title =NAVAL ORDNANCE AND GUNNERY, VOLUME 1, NAVAL ORDNANCE, NAVPERS 10797-A|publisher =U.S. Navy, Bureau of Naval Personnel|date =1957 edition|location =Washington 25, D.C.|quote=A loaded and fuzed projectile, seated in the bore of a gun that is hot from previous firing, presents a hazard, since detonation of the projectile is possible as a result of being heated.] This would destroy the mount.
Notes and references
* [http://www.navweaps.com/Weapons/WNUS_5-38_mk12.htm Detailed description and history 5"/38 including Ammunition and Mark data]
* [http://www.gyrodynehelicopters.com/5_inch_38_cal__gun.htm Illustrated descriptions of MK 30 & MK 38, list of ammunition for all Marks]
* [http://www.destroyers.org/Ord-Articles/5_inch_twin.htm Illustrated description of MK 38]
* [http://www.hnsa.org/doc/destroyer/fiveinch/index.htm Illustrated Operating Instructions for MK XXI model]
* [http://www.destroyers.org/Ord-Articles/destroyer_gun_ammunition.htm Photos of 5"/38 ammunition]
Wikimedia Foundation. 2010.