5"/38 caliber gun

5"/38 caliber gun
Two Mk 30 single enclosed base ring mounts on a Fletcher-class destroyer.
Type	Deck Gun
Place of origin	United States
Service history
In service	1934
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
Production history
Designed	1932
Specifications
Weight	Mk 12 Gun Assembly: 3,990 lb (1,810 kg). Mounts varied from 29,260 lb (13,270 kg) to 170,653 lb (77,407 kg)
Length	Mk 12 Gun Assembly: 223.8 in (5.685 m)
Barrel length	190 inch bore (4.83 m), 157.2 inch (4.00 m) rifling
Crew	Varied on mount type
Shell	53 to 55 pounds (24 to 25 kg)
Caliber	5 inches (127 mm)
Breech	Vertical sliding wedge
Recoil	15 inches (38 cm)
Elevation	−15° to +85°
Traverse	328.5 degrees
Rate of fire	Design: 15 rpm
Muzzle velocity	2,600 ft/s (790 m/s) new; 2,500 ft/s (760 m/s) average
Sights	Optical telescope

The Mark 12 5"/38 caliber gun is a US naval gun.

The gun is installed into Single Purpose^[1] 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,^[2] 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. United States naval gun terminology indicates the gun fired a projectile 5 inches (127 mm) in diameter, and the barrel was 38 calibers long, making the 5"/38 dual purpose midway in barrel length between the 5"/51 surface-to-surface and the 5"/25 anti-aircraft guns.

Among naval historians, the 5"/38 gun is considered the best intermediate-caliber,^[3] dual purpose naval gun of World War II,^[4] especially when it was usually under the control of the advanced Mark 37 Gun Fire Control System which provided accurate and timely firing solutions against surface and air targets. However, even this advanced system required nearly 1000 rounds of ammunition expenditure per aircraft kill.^[5] The comparatively high rate of fire for a gun of its calibre earned it an enviable reputation, particularly as an anti-aircraft weapon, in which role it was commonly employed by United States Navy vessels. 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.^[4] On pedestal and other mounts lacking integral hoists, 12 to 15 rounds per minute was the rate of fire.^[6] Useful life expectancy was 4600 effective full charges (EFC) per barrel.^[7]

The 5"/38 cal gun was mounted on a very large number of U.S. Navy ships in the World War II era. It has left 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.

Contents 1 Mark 12 5"/38 cal gun assembly 1.1 Characteristics 1.2 Loading and firing 2 Gun mounts 2.1 Types 2.2 Ammunition delivery 2.3 Mount crew 3 Ammunition 3.1 Projectile 3.2 Powder case 4 See also 5 Notes 6 External links

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 3,990 lb (1,810 kg).^[8] The Mark 12 Gun Assembly was introduced in 1934, where it was first used in single pedestal mounts on the Farragut class destroyers,^[9] 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.^[8]

Characteristics

The major Mk12 gun assembly characteristics are:^[4][8]

Semi-automatic 

Some of the recoil energy is used 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 through the muzzle.

Hand loaded 

A projectile-man and a powder-man are 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 ram is bolted to the top of the slide. This 5 to 7.5 hp (3.7 to 5.6 kW) system is designed to ram an 93 lb (42 kg), 47.5 in (1.21 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. Projecting from the rear 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 1,500 psi (10 MPa). During recoil, the pressure rises to about 2,200 psi (15 MPa).^[4]

Barrel 

The barrel of a 5"/38 caliber gun has a five inch (127 mm) bore and a length 38 times the bore diameter, or 190 inches (4.8 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 150 inches (3,800 mm).^[4][10] The initial velocity of a new gun is 2,600 ft/s (790 m/s). It is connected to the housing with a bayonet joint that allowed for replacement by destroyer tenders in the theater of operation.^[4]

Ballistics 

Maximum horizontal range, with a 55 pound projectile, is 18,000 yards (16 km).^[4] In the antiaircraft role, it had a ceiling of 37,200 feet (11,300 m) at 85 degrees elevation.^[10]

Armor Penetration with 54 lbs. (24.5 kg) Special Common Shell

5.0" (127 mm) belt armour at 4,000 yards (3,660 m)

4.0" (102 mm)at 5,400 yards (4,940 m)

3.0" (76 mm) at 7,400 yards (6,770 m)

2.0" (51 mm) at 11,000 yards (10,060 m)

1.0" (25 mm) deck armour at 13,800 yards (12,620 m)

with 55.18 lbs. (25.0 kg) AA Common Shell: 1.5" (38 mm) at 10,000 yards (9,140 m)

Range with 55.18 lbs. (25.03 kg) AAC Mark 49 (792 mps)

10° 9,506 yards (8,692 m)

15° 11,663 yards (10,665 m)

20° 13,395 yards (12,248 m)

25° 14,804 yards (13,537 m)

30° 15,919 yards (14,556 m)

35° 16,739 yards (15,298 m)

40°17,240 yards (15,764 m)

45° 17,392 yards (15,903 m)

AA Ceiling 37,200 feet (11,887 m)

US ships during World War II carried only small quantities of Special Common ammunition as the AA Common were considered more useful as all around multirole ammunitions, even if this meant much less armour penetration "Navy Weapons". http://www.navweaps.com. Retrieved 2010-09-19. . Bursting charges were 7.25 lbs.(3.3 kg) Explosive D Composition A, the Special Common had only 0,9-1,2 kg due to its thicker walls (AP).

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.^[10] 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.^[4] 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.^[10]

Gun mounts

Types

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),^[10] and later destroyers. It was also used on the island (starboard) side of the Essex-class aircraft carriers.^[4]

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.).^[4]

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.^[4]

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.^[4]

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.

5"/38 caliber gun mounts^[10]

Mark/mod	Barrels	Weight	Design	Use
Mk21	Single	31,200 lb (14,200 kg)	Open pedestal	Some 1930s built combatants, auxiliaries, merchant ships
Mk22	Twin	75,250 lb (34,130 kg)	Enclosed base ring	c1935 destroyer leaders
Mk24 Mod1	Single	29,260 lb (13,270 kg)	Open pedestal	1930s built aircraft carriers
Mk28 Mod0	Twin	156,295 lb (70,894 kg)	Enclosed base ring	Pre-Iowa class battleships
Mk28 Mod2	Twin	170,635 lb (77,399 kg)	Enclosed base ring	Iowa class battleships
Mk29 Mod0	Twin	108,000 lb (49,000 kg)	Enclosed base ring	Cruisers
Mk30 Mod0	Single	40,900 lb (18,600 kg)	Enclosed base ring	Destroyers, auxiliaries, USCG high endurance cutters
Mk30 Mod1	Single	33,500 lb (15,200 kg)	Open base ring	Destroyer rear mounts, escort carriers
Mk30 Mod69	Single	45,000 lb (20,000 kg)	Enclosed base ring	Destroyer escorts with the upper rear edge of the Mark 38 blast shield beveled to clear hedgehog projectiles from a launcher astern of the gun mount[11]
Mk32 Mod0	Twin	105,600 lb (47,900 kg)	Enclosed base ring	Cruisers, aircraft carriers
Mk32 Mod4	Twin	120,369 lb (54,598 kg)	Enclosed base ring	Cruisers, aircraft carriers
Mk38 Mod0	Twin	95,700 lb (43,400 kg)	Enclosed base ring	Destroyers, Atlanta class light cruisers

Ammunition delivery

Since this gun fires semi-fixed ammunition, each round is delivered to the gun in two pieces — a projectile and a powder case.^[4]

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.^[4] 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.^[4] The powder case is sent up through a powder scuttle in the gun room's deck just next to the powder man's feet.^[4] 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 held closed, and the gun fires as soon as the breech closes), the crew move 30 to 44 projectiles and 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.

Mount crew

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.^[12] 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 Marine ships 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 reticule 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.^[13] His duties during Automatic Control was to receive action orders from the battery commander (e.g.: "Mount 51, plot. Surface action starboard. Target destroyer. Bearing 060. Range nine thousand, five hundred yards. 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 process 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.^[13] His duties are the same in automatic or local control.

Pointer 

Controls the mount's elevation and firing. He sits in the left front corner of the mount. In front of him, are his optical sight, hand wheels, and elevation drive controls. Between his knees is a large box called the Elevation Indicator Regulator. (pictured) This box controls the elevation power drive. Through a window on top of the box, he sees a set of dials that indicate the elevation of the gun, and the automatic elevation orders coming from the Fire Control System. To his right, is the Electrical Fire Select Switch. It is a rotary switch with three positions: Off, Local, and Auto. Off disables the electrical firing system on the mount. Local enables the electric firing key on his right hand wheel. Auto enables the off mount electrical firing circuit from the fire control system. Just outside of his right knee, is the Percussion Firing Select Lever. This mechanical lever has two positions: Safe, and Armed. When it is in the armed position, the mechanical linkage for percussion firing is enabled. His right footrest is at one end of this linkage, and the firing pin sear in the breech block is at the other. By rocking his right foot forward, he fires the gun. Electrical firing is the primary firing method, and percussion firing is armed if the electrical firing system fails. When the Mount Captain commands, "Match pointers. Switch to Automatic.", he looks down at the dials on his Indicator-Regulator. The dials tell him the difference between the gun's present elevation and the ordered elevation electrically coming from the Fire Control System by synchro. 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 command of the Mount Captain, he fires the gun by squeezing the firing key on his right hand wheel.

Trainer 

Controls the mount's train angle (bearing). He sits in the right front corner of the mount. (See the far right man in the Mk21 open mount picture.) In front of him, are his optical sight, hand wheels, and train drive controls. Between his knees is a large box called the Train Indicator Regulator. (pictured) This box controls the train power drive. On top of the box, is a window with a set of dials that indicate the train angle of the gun, and the automatic train orders electrically coming from the Fire Control System by synchro. 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 

Operates the sight setting equipment. In single mounts, he stands just behind the trainer (See the man with headphones in the Mk21 open mount picture), while in twin mounts he sits between the guns, just forward of the projectile hoists. The sight setter moves the sights' reticules relative to the barrel's axis. In early open mounts, this was done by moving the platforms to which the sights were bolted. Sights in enclosed mounts have movable prisms in their optical paths.^[14] The sight setter has three dials, and two hand cranks. (pictured) The two right dials and right hand crank control the elevation reticule offset (called Sight Angle^[15]). The upper right dial is scaled in minutes of arc, and the lower right dial is in yards. The left dial and hand crank control the reticule's left and right offset (called Sight Deflection^[16]), and the dial is scaled in angular mils. When the mount is in Automatic Control, he turns his hand cranks to keep index marks on his dials matched to lines on the central disks of the dials. These disks are electrically controlled by the Fire Control System by synchro.^[17] This is called matching the pointers,^[17] 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 

He operates the equipment which sets the fuze time on projectiles with mechanical time fuzes. On a single enclosed mount, he sits below and just outboard of the Pointer's seat. Under the Pointer's seat, and in front the Fuse Setter, is the Fuse Indicator Regulator. (pictured) It is a box with a window, a hand crank, and a selector lever. On a twin mount, he and his Fuze Indicator Regulator sit next to the Sight Setter between the guns. When the mount is put in Automatic control, he flips the selector lever to Auto, and this electrically powered Fuze Indicator Regulator automatically follows the fuze setting orders sent from the Fire Control System by synchro. 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.

Ammunition

This gun uses semi-fixed ammunition. (pictured)^[4] Each round consists of a projectile, and a powder case.

Projectile

The Projectile has three major parts: the body, the fuze, and the explosive charge.

Projectile body

The 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.^[18]

Fuze

The 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"/38 cal projectile experiences at least a 14,000 g acceleration as it is pushed down the barrel.^[4] This acceleration cause parts of the fuze to setback due to their inertia, and they shear pins that hold them in the unarmed position.^[4] The second event is the spinning of the projectile due to the bore's rifling. The 5"/38 cal projectile spins at more than 200 revolutions per second when traveling at 2,600 feet (790 m) per second (New gun initial velocity).^[4] 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:^[4]

Mechanical time fuze

A nose time fuze that detonates the shell after an adjustable time interval has elapsed since firing.^[19]

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, allowing the projectile to penetrate the target prior to detonation.^[4]

Point detonating fuze

A nose impact fuze. Very fast detonation on the surface of the target.

VT fuze

The VT (Variable Time) fuze is a proximity fuze.^[20] It is a nose electronic fuze that does not require impact to trigger.^[21] 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.^[22]

5"/38 cal projectiles^[4][8]

Body label	Full name	Description
AA	Anti-aircraft	A high capacity fragmenting shell with a nose mechanical time fuze
AAC	Anti-aircraft common	A medium penetrating shell with a mechanical time fuze and a base detonating fuze. Designed to be used on either aircraft or lightly armored ships. For aircraft, the time fuze is set to explode the shell just before it reaches the target. The detonation shock wave and the expanding cone of shrapnel increases the chance of target destruction. For vessels, the time fuze is left on safe, and the base detonating fuze will explode the shell 25 milliseconds after impact.
AAVT	Anti-aircraft VT	A high capacity fragmenting shell with a VT (proximity) fuze.
AP	Armor-piercing	A thick walled penetrating projectile with a base detonating fuze. The explosive charge is usually Explosive D because it is less sensitive to impact.[4]
SS	Star shell	A thin walled shell with a mechanical time fuze. Packed inside is a flare attached to a parachute. When the fuze fires, a small black powder charge expels the flare and parachute out the back. Before radar, star shells were used to illuminate the target at night. They are still used in support of troops at night, or illumination of an at sea rescue.
WP	White phosphorus	A thin walled shell with a point detonating fuze used for smoke screens. It also has some incendiary effect.
AA non-frag	Anti-Aircraft non-fragmentation	A thin walled shell with a mechanical time fuze and packed with a smoke producing chemical that is ejected out the rear by a small black powder charge. It is used in practice anti-aircraft shoots.
AAVT non-frag	Anti-Aircraft VT non-fragmentation	A thin walled shell with a VT fuze and packed with a smoke producing chemical that is ejected out the rear by a small black powder charge. It is used in practice anti-aircraft shoots.
BL	Blind load	A shell without a fuze, and filled with sand. It is used in practice surface shoots.
W	Window	A thin walled shell with a mechanical time fuze and packed with strips of metal foil that is ejected out the rear by a small black powder charge. It is used to confuse enemy radar.

Powder case

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.^[23] 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.^[10] 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 from the muzzle. It is important to clear the projectile through the muzzle. It is not easy or safe to back the projectile through the chamber with a bore rod pushed down the barrel from the muzzle.^[24] 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.^[25] This would destroy the mount.

See also

• QF 4.5 inch Mk I – V naval gun British equivalent
• List of naval guns
• List of naval anti-aircraft guns
• Naval gunfire

Notes

External links

• Detailed description and history 5"/38 including amunition and Mark data
• Illustrated descriptions of MK 30 & MK 38, list of ammunition for all Marks
• Illustrated description of MK 38
• Illustrated Operating Instructions for MK XXI model
• Photos of 5"/38 ammunition
• Naval Ordnance and Gunnery, 1957 Volume 1 Naval Ordnance NavPers 10797-A