|United States of America
5"/38 (12.7 cm) Mark 12
The 5"/38 (12.7 cm) Twin Mount Mark 32
1. Trunnion28. Elevating arc (fixed to gun slide)
2. Gun port shield29. Training gear motor
3. Training gear handwheel30. Sight-setter's seat
4. Right gun carriage31. Training connecting shaft
5. Training indicator regulator32. Sight-setter's indicator
6. Training gear box, B-end33. Fuze-setting indicator regulator
7. Training gear box, A-end34. Trainer's Telescope
8. Barbette (fixed to ship)35. Trainer's seat
9. Ventilating system motor36. Rammer pump
10. Ready-service projectile stowage in handling room37. Case ejector chute
11. Projectile hoist (mount)38. Voice tube
12. Projectile hoist (ship)39. Ammunition hoist motors, under captain's platform
13. Powder hoist (mount)40. Mount captain's platform
14. Powder hoist (ship)41. Hatch
15. Ready-service powder stowage in handling room42. Elevating gear motor
16. Base ring (training rack on inside)43. Checker's telescope
17. Air intake compartment44. Pointer's seat
18. Case ejection chute door on back of shield45. Pointer's telescope
19. Air vent trunk46. Pointer's foot firing pedal
20. Auxiliary case-ejection port, in back of shield47. Elevating cross-shaft
21. Case ejector48. Fuze-setter's seat
22. Roof hatch counterbalance49. Roof hatch
23. Mount captain's blast hood50. Rear access door
24. Open sight51. Foot rungs
25. Air intakes52. Side access door retaining hatch
26. Rammer motor53. Side access door
27. Right gun slide
How the 5"/38 crews operated
By Dick B. - Updated 11 September 2001
The 5"/38 gun mounted in Destroyers was carried in single and twin mounts.
The Trainer sat on the right side of the gun, with a vision port/sight and the
Pointer on the left, also with a vision port/sight. The Trainer moved the mount
in bearing (azimuth) while the Pointer moved it in elevation. Both stations had
'follow the dial' instruments for Director control or by Main Battery Plot, and
the means for local control, which meant the Pointer and trainer, actually aimed
the guns. This was true of both single and twin mounts. The seats were those
perforated steel tractor type which got pretty uncomfortable after a while.
The Director, of course, was located above the Bridge and had the rangefinder
and radar gear. Four men, including an officer, manned it. Main Battery Plot
was located below, right aft of the Mess decks, in the IC Room, with the main
gyro. Guns could be fired from the Director, Plot or locally. It was the
practice in most ships for all firing keys to be closed at the command "Fire" so
that the circuit would be completed, no matter what.
On twin mounts, projectile hoists were located between the guns, serviced by the
upper handling room, immediately below the mount. Projectiles were carried nose
down, the fuse being set automatically by the mechanism in the hoist. Projectile men were trained to wait until the last possible instant to remove
the round from the hoist, as the fuse setting was constantly being adjusted.
The projectile weighed around 55 pounds and was painted and stenciled according
to its purpose. They had a brass rotating band toward the base, which was sharp
and occasionally cut one's palm as the round was handled.
It was the drill to grasp the projectile firmly at the base with the right hand
(for the right hand gun) pulling it into the left hand about midway along the
ogive. It was raised to a 'Port Arms' position across the chest, then laid in
the tray ahead of the powder case. The Projectileman had, of course, to wait
for the Powder man. Once all was set, the Projectile man hit the rammer lever
with his right hand, in passing en route to the hoist to grab another round.
The hydraulic rammer stuffed the packet up the spout and tripped the breech
stop, allowing the vertical breech to slide up and close. The breech slid in
bronze rails and there was a fair amount of polished brass and gleaming steel,
necessary for the mechanical functions. Paint could foul or otherwise gum up
the works, so nothing important was painted.
The Powder man stood immediately to the rear of the Projectileman, and received
his goods through a scuttle in the deck plate, shoved up from the handling room
below. The cartridge case came with a protective steel fitting over the primer,
called a 'butterfly', which the Powderman had to knock off as he pulled the case
up from the scuttle. This required a certain dexterity of the wrist, as the
butterfly had a small ring handle on it, to help the loader lift the 35-pound
charge. One didn't want to flip the butterfly off before having solid control
of the cartridge, you understand. Having done his gymnastics, it remained to
throw the case onto the tray, steadying it with the left hand, while the first
loader manipulated his projectile. This also required some athletic ability, as
the gun was wildly training and elevating, trying to track a 'fast mover. Immediately to the Powder man's right rear, the Hot Shell man stood, armed with
a huge Asbestos mitt, to catch the fired casing and discharge it through the
port provided in the rear of the gun house. These, being propelled from the
breech at really healthy rate, could be a serious embarrassment to a gun crew,
should this worthy fail, and allow them to ricochet around the interior of the
mount. He had to be very fast and very accurate. He only got the one chance,
you see. Normally the gun fired and ejected instantly.
The Gun Captain stood to the right rear of the gun, on a little elevated stand,
supervising this orchestrated chaos. His was the responsibility for manually
operating the breech in the event of power or hydraulic failure and commanding
the crew in local control.
The Mount Captain commanded the mount, and operated the sound powered phones,
passing orders and giving firing data as needed, and controlling the mount in
local control. He perched on an elevated throne at the rear of the gun house
between the guns in a twin mount, with a hatch he could stand in, the better to
see his targets, etc.
In a twin mount, firing against aircraft, in a lively ship coursing through any
sort of sea at all, life in the gun house was intense at times. It was invariably hot, an acrid odor of powder fumes permeated the place, a thin veil
of smoke filled the air, and, for some reason, the unfired powder cases and projectiles had this peculiar sour smell, which burnt the throat and eyes.
Imagine trying to maintain footing on heaving deck plates slick with hydraulic
oil mist; hustle 55-pound high explosive shells into a gun now vertical, now at
forty five degrees and now vertical again, all in a third of a second, for the accepted standard was twenty rounds a minute, bar nothing.
As the gun elevated, the breech end descended smartly into a well in the deck
plates. It was not unknown for gunners to lose legs and feet as the heavy
breech dropped down at an unfortunate moment. It has been known that gunners
were mashed into chili by the breech, as a result of an untimely lurch. There
was no warning or time for one, really, one had to keep his wits about him.
The hoist hung under the gun, into the upper handling room. That space did not
move with the mount, as does a turret, but merely with the ship. The compartment is circular, and holds all the ready service ammunition in racks
along the bulkhead. The Shell man handles the projectiles and the Powder man
the cases. In his case, he simply grabs one and shoves up through the scuttle
to the Powder man above. All charges are the same.
The Shell man, however, has to grab the selected round from an assortment around
the compartment and hustle it to the hoist, set it in the cup properly, lest he
jam the hoist, and see it on its way. Both are working in a stifling hot,
heaving space filled with the noxious odors and, I might add, no hope of surviving if something goes amiss.
Below them, in the Magazine, a crew keeps the handling room supplied with the
necessaries, manually humping the projectiles and powders in conditions even
worse than those above them.
I know of one ship where Mount 52 fired just as Mount 51 opened the breech of
the right hand gun, the mounts were so trained and pointed, that a flashback
occurred from the muzzles of Mount 52 into Mt 51. Powder was ignited and all 17
men were killed instantly. Had a projectile gone off, the ship could have been
lost. The Navy subsequently built some sort of stops into the firing circuits
to prevent a recurrence.
The guns' crews are made up of Seaman branch sailors, mostly from the deck
force. Bosun's Mates make up the gun crew's petty officers, in the main. Gunner's Mates are the 'tech's but also serve as Mount Captains and sometimes,
Gun Captains. The Director is manned by Fire Controlmen, as is Plot. The
Gunnery Officer may be in the Director or in Plot.
Unquestionably the best Dual Purpose gun of WWII, this weapon was designed to arm the new destroyers being built in the 1930s. The 5"/38 (12.7 cm) was used on nearly every major US warship built between 1934 and 1945 and was still being used on new construction as late as the 1960s. It was also used on many auxiliaries and smaller warships as well as US Coast Guard vessels. This
standardization, unique in any navy, greatly helped the logistical supply situation of the Pacific War.
There were some teething troubles when this gun was introduced in 1934, but long before the start of WWII 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.
These guns were hand-loaded, but power-rammed which gave them a high rate of fire and made them capable of loading at any angle of elevation, both necessary qualities in an AA weapon. 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 mounting. However, starting with USS Craven (DD-380), a new base-ring mounting with integral shell and cartridge hoists on the axis of the mounting was introduced. This type of mounting meant that shells and cartridges could be passed directly to the gun's breech at any angle of training, thus improving the rate of fire. Most subsequent designs including all twin mountings were similar, although a simpler base ring type lacking hoists was introduced in 1943 for use on auxiliary vessels. The introduction of VT AA shells in 1943 made this weapon an even more potent AAA gun.
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 building 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 famous weapon that used semi-fixed ammunition.
Of autofretted monobloc construction and used a semi-automatic vertical sliding wedge breech mechanism. The gun barrel was secured to the housing by interrupted threads, thus allowing easy barrel replacement. About 8,000 of these weapons were produced between 1934 and 1945.
Early units of the Atlanta Class light cruisers carried sixteen 5"/38 (12.7 cm) guns which gave them the heaviest AAA broadside of any USN warship.