The Patriot Files Forums - Okay, sailors, help me out here...

The 3"/50 had a taper to it and the 5"/25 , 5"/38, 5"/50, 5"/64 all are straight cased

United States of America
3"/50 (7.62 cm) Marks 27, 33 and 34
Pictures
http://www.navweaps.com/Weapons/WNUS...33-34_pics.htm

A series of 3" (7.62 cm) AA guns dating back to World War I. These were of a simpler construction than the previous 3" (7.62 cm) guns and successive marks were to improved designs. This gun was widely used up to the mid-1930s, but were then gradually replaced on larger ships by 5"/25 (12.7 cm) single mountings and later by Bofors 40 mm in twin and quad mountings. However, the battleships New York and Arkansas still had them as late as 1943. During World War II this weapon was extensively used on smaller warships such as destroyer escorts, submarines and auxiliaries along with many merchant ships with about 14,000 guns being produced between 1940 and 1945.
Although considered to be dual-purpose weapons, these guns had limited effectiveness in either role, as they fired light-weight shells and were manually operated, meaning that they could not be fitted for RPC. However, the invention of the VT fuze and the addition late in the war of power operation together with the Mark 51 director system greatly improved their effectiveness as AAA guns, giving the later marks of this weapon a new lease on life. In the fall of 1945, CinCPac considered that a 3"/50 (7.62 cm) with director control and VT ammunition was superior to a twin Bofors 40 mm mount and at least equivalent to a quad Bofors 40 mm mount.

http://www.navweaps.com/Weapons/WNUS...10-22_pics.htm

5"/25 (12.7 cm) Marks 10, 11, 13 and 17
Updated 12 February 2008

--------------------------------------------------------------------------------

This was the first USN heavy AA gun designed for the purpose and was used on most USA capital ships and cruisers built or modernized between 1926 and 1940. When these weapons started to appear on battleships, the gunnery officers began thinking of them as dual-purpose weapons and often fired them in the annual surface gunfire contests with impressive results.
The mountings for this weapon were deliberately lightly built in order to give them the lowest possible moment of inertia and thus the highest possible speeds for manual training and elevation. As a result, these guns had about one-third the moment of inertia for train as did the 5"/51 (12.7 cm) anti-torpedo boat mountings. This requirement led to a short barrel in order to keep the weight down which resulted in a relatively low muzzle velocity, but this was considered to be acceptable for an AAA weapon. In the early 1930s these guns were briefly considered for arming new construction destroyers, but they were ultimately rejected in favor of a new design, the famous 5"/38 (12.7 cm) Mark 12.

On 15 February 1942 while escorting a convoy near Timor, USS Houston (CA-30) was attacked by nine Kawanishi H6K Type 97 ("Mavis") four-engine flying boats and thirty-six Mitsubishi Ki-21 Type 97 ("Sally") twin-engine bombers and claimed to have shot down seven of them with these guns. She fired 930 rounds during the 45 minute action, an average of 2.6 rounds per gun per minute.

All early models were constructed using a monobloc barrel. The prototype was a Mark 3 Mod 0 cut down to 25 calibers and then designated as Mark 3 Mod 3. The Mark 10 Mod 0 had an autofretted barrel with a threaded and shrunk-on housing and used a vertical semi-automatic sliding breech block. the Mark 10 Mod 1 used a threaded barrel keyed to the housing. Mark 10 Mod 3 had part of the left housing cut away to ease loading. The Mark 11 added chromium plating to the bore. Mark 13 was similar to the Mark 11, but the barrel and housing were joined by a bayonet joint to allow easy barrel replacement, a feature found in all subsequent US 5" (12.7 cm) designs.

The Mark 17 was a "wet mount" version for submarines and was unusual in that it did not require breech or muzzle plugs. This was because it used a special liner resistant to corrosion from sea water and could thus be submerged and flooded without harm to the gun. The Mark 17 Mod 0 used a tube of higher strength steel than that used for earlier Marks with a shrunk forged copper-nickel alloy liner. The Mark 17 Mod 1 was a bored out Mark 13 Mod 0 fitted with a tapered copper-nickel alloy liner and used semi-fixed ammunition in order to ease handling on submarines. Both Mark 17 mods had chrome-plated bores and neither had the pneumatic rammers used on other Marks. This was acceptable as the Mark 40 mounting used on submarines was an SP type with a maximum elevation of 40 degrees.

Battle of the Eastern Solomons - 24 August 1942 (Read More...)

--------------------------------------------------------------------------------

U. S. S. ENTERPRISE
1 September 1942
From: Gunnery Officer.
To: Commanding Officer.

Subject: Attack by Enemy Aircraft on U.S.S. ENTERPRISE August 24, 1942.

The following report of the action on 24 August 1942 is submitted:
Shortly before 1700 enemy planes were reported approaching at a range of 88000 yards on bearings of 300° to 310° true. Fighters were sent out to intercept and when the range was 40 to 50 thousand yards the fighters reported that there were many dive bombers and torpedo planes. The weather was clear with ceiling unlimited and ordinarily we would have sighted the planes at this range except that they were dead astern and into the setting sun. Radar reports were received until the range was 16000 yards but we were unable to pick up the planes in either director, nor did the lookouts sight them. During most of this time the ship was launching planes.

About two minutes after the last plane of our attack group had been launched, 1st Sgt. Shinka, the battery officer on 20 mm battery #4, sighted a puff of smoke high on the port bow and soon made out a dive bomber coming down. One gun commenced firing immediately although the range was about 4000 yards. This immediately brought every ones attention to the planes however, and by the time the plane was within firing range all guns in that sector were on and firing. The starboard batteries were also brought to bear across the flight deck. The first bomber was brought down in flames and each one following was subjected to the same fire.

After about three planes had come in from the port bow another group was sighted diving from the port quarter. These were immediately taken under fire by all after guns which could bear. The Jap bombers apparently came from two directions, about 090° T and 0° T. The relative bearing of the first attacks were broad on the port bow and port quarter. The relative position changed as the ship was swinging but the true direction remained nearly constant. The planes came from each of these two directions, about one each ten seconds from the next three or four minutes. There were two short lulls of 20 to 30 seconds, but generally the timing was consistent.

The planes were at an altitude of 16 to 20,000 feet when they started their dive and some observers state that they came down to about 10000 feet in long circles and then started to dive.

Since the planes had not been picked up by the directors, the guns were left in local control. The directors continued to search the areas in which torpedo planes were constantly being reported coming in, but none were ever sighted. The five inch guns used precut fuses of 1.5 seconds with excellent results. Open sights were generally used although one guns crew reports that they would shift to telescopic sights after picking up the planes. No difficulty was experienced in keeping on the planes. The five inch bursts from this ship were well under the bursts of all other ships firing and were generally well in line and ahead of the planes. Several planes were noticed attempting to pull away from the bursts, others were seen to emerge from a burst on fire and three planes were reported to blow up as though hit directly with a five inch projectile. It is considered that the use of influence fuzes with the five inch guns would make them devastating against a dive bombing attack.

After the first bomb hit aft all power failed on the five inch guns aft and the guns had to be trained, elevated and loaded by hand. Hand ramming reduced the rate of fire of these guns by more than half. A better system of hand ramming should be devised and is being worked on.

Local control using sights and tracer spotting was used on the 1.1 mounts. Some difficulty was experienced in picking up the targets and in getting the fire on the planes but generally the fire seemed to be very effective. The hand train is not fast enough to keep up with the turning of the ship. The newly installed 1.1 mount on the forecastle was about the only gun firing on a plane diving from dead ahead and the plane crashed into the sea without dropping its bomb.

The 1.1 mounts are greatly handicapped when shooting to port because of the limited arc of train. Several instances occurred of planes being under fire and the swinging of the ship put the planes outside of the arc at which the gun could bear just as the plane came within the most effective range. It is strongly recommended that the forward mounts be moved further forward and the after mounts more aft.
At least fourteen planes were seen to fall in the water or burst in the air close aboard the ship. Other planes were observed to fall further away. I personally saw four of them fall at ranges 10 to 15 thousand yards when I was searching for reported torpedo planes. All planes were taken under fire and probably damaged.
Ammunition Expended: 5"/28 AA Common 97 rounds
1.1 1500 rounds
20 mm 12280 rounds
.50 caliber 885 rounds

Personnel Casualties: (Omitted)
The control of the 20 mm guns was local. Tracer control was used by the gunners. The deflection problem was practically nothing and the fire was very accurate. The tracers from all guns appeared to converge right at the nose of the diving planes and many broke into flames while still high and did not drop their bombs. Few, if any, planes dove without being fired upon by the 20 mm guns and their fire was particularly effective. It is probable that every attacking plane was severely damaged and possibly none of them returned to their carrier.

The rapidity with which the 20 mm guns can be brought to bear on any target and shifted to each target, is its principal advantage against dive bombers. Its disadvantage is its short range. Our five inch bursts being placed at 1200 yards made the determination of the best opening range relatively easy. In very few cases did the guns stay on an attacking plane after it had dropped its bomb or appear to be in flames. It is recommended that additional 20 mm guns be placed at all available spaces along the flight deck, particularly on the port side. If enough of them can be provided we should have little to fear from dive bombers.
Material Casualties:
Group III, five inch guns #5 and 7 were completely wiped out by a bomb hit which exploded within three feet of the ready service powder box.

The power to Group IV five inch guns was out after the first bomb hit. This caused a greatly reduced rate of fire on those guns. The upper ammunition hoists were also put out of alignment and cannot be operated.

The decks and bulkheads around Group IV began getting hot from adjacent fires so all remaining ammunition was thrown overboard except 5 rounds per gun. This proved to be an unnecessary precaution however as the fires were put out before they had spread dangerously. The ammunition hoists had been subjected to considerable heat so as soon as possible they were disassembled and the powder and shells removed and thrown overboard. The upper powder charge in the hoist to gun #5 had burned and many powder tanks were bent and crushed within the hoists.

The casualties on the 1.1 mounts were not heavy. On both mounts #1 and #2 the opening of fire was delayed a few seconds because the pointer pressed his foot firing pedal before the safety lever had been thrown. The safety lever cannot be operated if the foot firing pedal is down and it is a little difficult to tell the pointer to release the pedal in the noise of battle. A better safety system should be devised.

Many bomb fragments struck mounts 3 & 4 and one gun on mount #3 was put out of commission. The water cooling line to mount #4 was severed and three of the cooling jackets were punctured. Fortunately this happened at the end of the firing and the guns could have been fired about a hundred more rounds apiece. One gun on #4 was also put out of commission by a bomb fragment. The gun would not return to battery. The punctured water jackets and damaged gun have all been renewed with spare guns.

A great deal of trouble was experienced on the 1.1 mounts from water caused by near misses. The water was nearly knee deep at times and made the deck very slippery. When the ship was heeled over in a turn, which was most of the time, the loading crews had great difficulty in retaining their footing, and at times could not keep up with the firing. Serious consideration should be given to devising a non skid surface some what similar to that used around swimming pools. The great deluges of salt water did not seem to affect the ammunition.

The 20 mm guns fired nearly continuously with very casualties. Three jams were reported. In two of the guns the barrel was removed and another barrel inserted and in the other the gun was cleared and continued firing. A bomb fragment struck a magazine on gun #5 of battery #6, exploding the magazine. The gunner was seriously wounded. Another magazine was tried but failed to fire. The barrel was then changed and firing was resumed. A near miss directly below battery #8 knocked the members of the crew down, the magazines were knocked from the guns and the bolt released. The gun went forward and jammed. The guns were recocked, reloaded and firing resumed. Several magazines on this battery were bent and crushed.

Only two casualties occurred on the .50 caliber guns. One round failed to fire, the gun was recharged and continued firing. A broken firing pin occurred on battery #2. This was renewed and firing continued.

The after director was badly shaken by the bomb hit at #2 elevator. The shaft feeding the position angle to the range keeper was broken and the range keeper will have to be lifted to be repaired.
Miscellaneous: Conclusions and recommendations:
The nettings rigged outboard of the 1.1 mount splinter shields proved very useful.
Great difficulty is experienced in communications between the pointer, trainer, and battery officer on all guns, mounts, and in the directors, during the noise of a battle. Serious consideration should be given to devising a throat microphone and headset or to incorporating the pointing and training into one man. This same difficulty is experienced in the 20 mm batteries. It is almost impossible for the battery officers to communicate with their gunners except by grasping them and pointing or gesturing.
The shaking of the ship when hit or when a near miss occurs is violent. In the ammunition handling rooms, five inch projectiles were hurled from the bins and bombs in the magazines were tossed in the air and bounced on deck. The decks in the bomb magazines should be equipped with pad-eyes similar to those in the hangar deck so that bombs can be secured to the deck. The five inch projectile bins should all be equipped with a holding-down piece which can be lowered down to the projectiles as they are removed from the bins.
The lookouts report that torpedoes were sighted, <illegible> in the water, some distance from the ship. Two wakes were also reported but could not be verified.
Some means should be provided to determine if a magazine or the pyrotechnic locker has actually been sprinkled, without opening the door.
A portable foamite connection to insert in a fire hose would be desirable.
(Signed) O. L. LIVDAHL
Lieut. Comdr., U.S.N.
Gunnery Officer.

--------------------------------------------------------------------------------
Flack http://www.history.navy.mil/photos/i...000/g20989.jpg