Rn vs IJN

Wild_Bill_Kelso said:

yeah my whole categorization system for AA guns is pretty much rubbished by your very relevant point though lol

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I think you do have fair points about the comparison between powered and unpowered mounts.

Yeah but I guess it's kind of a branch now...? Anyway, I've confused myself. Time to quit reading war boards and go plunge back into reality for a while... catch y'all later

Wild_Bill_Kelso said:

Yeah but I guess it's kind of a branch now...? Anyway, I've confused myself. Time to quit reading war boards and go plunge back into reality for a while... catch y'all later

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Yeah, I'm getting ready to start rereading Lundstrom's First South Pacific Campaign, this thread has me more interested in IJN capabilities and I need to refresh my knowledge.

Shortround6 said:

There was a lot of back and forth going on and lot of it was either test or theory and not actual combat.

British were laying down the L class in 1938-39 so planning began ???
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Guns elevated to 50 (?) degrees, They were actually pretty much a waste of time and effort. In part because they only armed 12 destroyers with them (and nothing else) so they are little more than a foot note. The whole thing sounds good on paper but didn't work in practice. The ammunition hoists in the center of the mount (not turrets) didn't turn so if the guns were firing at 90 degrees the ammunition hoists were still lined up with the center of the ship. The mounts used manual elevation, did not have power rammers and while traverse was powered it was slow. Basically they weren't any better and were probably worse than the older 40 degree elevating mounts. Four of the ships had four twin 4in mounts and were practically little AA cruisers They also worked rather well in close range night battles with their high rate of fire. Again, practical experience vs theory.

Swiped from a foot note on Wiki.
Hodges, Tribal Class Destroyers, p32: Diagram of High Level Bomber Attack: A 240mph target, at 12 thousand feet altitude could expect to be under for fire about 75 seconds, from the time it enters the effective range of the HACS until it flies to within the minimum range of a 5.25 gun elevated to 70 degrees. A Tribal class destroyer with 40-degree elevation guns would be able to engage the same target for about 37 seconds.

Now we are comparing two different guns here and the 5.25 gun does have a much longer range than the 4.7 gun but the 4.7 gun in question only has a 10-12 rpm firing rate so basically you get about 8 shots per barrel at best as the plane goes from max range to the inner range where the gun can't elevate high enough anymore until the plane is departing.
Also bombing from 12,000ft actually didn't work so that bombing profile went away.
I am wondering about the steep dive approach used by the Swordfish and Albacore???
Go in over the "top" of the low angle enemy guns, dive down and level out close to the ship where the enemy has to reacquire the attacking aircraft and only has enough time for 2-3 shots?

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Only 12 destroyers came to be fitted with the Mk.XX mount because WW2 happened in 1939 for Britain.

These mounts were designed to be equipped with a new model of 4.7" gun, the 4.7"/50 QF Mk.XI, designed to fire a new heavier 62lb shell with a greater anti-ship hitting power because in 1937 that was what the RN felt it required to combat the ever increasing numbers of large destroyers being produced by Germany & Japan. Immediately pre-war it was realised that the L & M class and proposed successors couldn't be built in the required quanties (cost, size & complicated) so an "Emergency" destroyer type had to be developed & quickly. So the O/P classes were ordered on 4 Sept 1939 to be armed with the best gun that could be quickly mass produced. That meant reverting to single 4.7" mounts, and, as no single mount for the Mk.XI had been produced, they reverted to the 4.7"/45 QF Mk.IX with its 50lb shell that had been in use since the late 1920s in single & twin mounts from the A class to the J/K/N classes. Those guns then formed the basis of the armament of the O-W Emergency/Intermediate classes ordered from 1939-1941 with an increase to 55 degree elevation in later the later classes but using the same gun. Then the switch to the 4.5" calibre was made in the Z & C classes. A new line of destroyer development then began in 1942 with the big Battles.

There were delays manufacturing the Mk.XX mountings, so 4 of 8 of the L class were completed with 4 twin 4" instead in order to try to shorten the build time at a time when more fleet destroyers were desperately needed. That, amongst other things, also drove the decision to complete 12 of the 16 O/P classes with single 4" HA guns instead of the planned 4.7"/45. Had war not broken out in 1939 the RN would undoubtedly have produced more destroyers of different designs with the Mk.XI gun.

In designing the Mk.XX mount the RN was seeking a fully enclosed mount to make life easier for gun crews in heavy weather who were having to move the new heavier shell. That then meant proving a hoist system from below decks, and the method chosen, which proved unsatisfactory in practice, was a fixed hoist system rather than one that rotated with the above deck gunhouse. That in turn meant that the ammunition handlers had to stand between the guns, which moved them outboard and meant in turn that they had to be made to elevate separately. This was driven at least in part by trying to minimise cost and potential weight. As it was weight went from 10.6 tons for a single 4.7"/45 to 25.5 tons for the twin Mk.XIX in Tribal/J/K/N to 34 tons for the Mk.XX. That in turn meant a bigger ship which in turn drove up cost which was becoming a real issue in 1939. (The increasing cost of destroyers meant that in 1939 the second flotilla became the N class as a repeat of the J/K design instead of the L/M class - the saving was estimated to be about £50,000-60,000 per ship in 1939 terms)

The mount did demonstrate an increase in elevation from 40 to 50 degrees but that was to make best use of the new more powerful gun (they were able to increase the max range from 17,000 yards at 40 degrees of earlier ships to 21,240 yards at 45 degrees in the Mk.XX). It was never seem by the RN as being intended as any kind of true "dual purpose" weapon in the way that the various 4.5" turrets being developed for battleships and carriers were.

Here is a drawing that explains the HA AA problem.



Pre-war the answer to the dive bomber was seen as the pom-pom and the quad 0.5".

From 1937 Britain sought a replacement for the 0.5". It settled on a modified 20mm Oerlikon design in 1939 and ordered a large quantity direct from Switzerland for delivery in 1940. The unexpected fall of France meant that the bulk of these could not be delivered. fortunately they also a acquired a licence to allow production in Britain, but there were considerable difficulties getting the factory up and running in wartime Britain. As a result it was autumn 1941 before production guns began to roll off the production lines.

ThomasP said:

It was not until integrated radar FC systems matured that the proximity fuze became really effective at longer ranges. The post-war FC systems on RN Leander class frigates, for example, were considered to only need 2 salvos from their twin 4.5" turret to achieve a 80% chance of a kill vs an aircraft attacking the firing ship. Crossing targets still presented a more difficult firing solution but much less so than in WWII when it was almost a matter of luck or individual crew talent rather than method.

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Some context. I served on HMS Tiger and on one of her last live firing AA shoots, she shot the target down with her second 6in shell. The Gunnery officer lost a bet as he said that it would be the first shell.
Pretty impressive

Wild_Bill_Kelso said:

This was also how it works with ships too, as defensive warships like cruisers and destroyers were often positioned around, and at some distance from (as in miles) the primary target - which might be an aircraft carrier, a troop transport or supply ship etc. Standard US navy formations for a carrier task force in WW2 were around 12,000 yards wide. With really large task forces they got a lot bigger than that. Many WW2 aircraft that attacked ships did so with torpedo attacks, rocket attacks, or strafing, which had to be done from quite close and at low altitude. Torpedo runs in particular required not only low but slow, particularly during the early years of the war (this improved later with the wooden carapice they added to them, allowing higher speed and higher altitude drops). So these aircraft most certainly were vulnerable to heavy machine guns and in fact, were routinely destroyed by them.

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Again be careful about "Standard US navy formations".

The US started in 1942 with its pre-war doctrine which then evolved through that year. On 13 April 1943 Nimitz ordered a total rewrite of the then "Standard Cruising Instructions for Carrier Task Forces" which was issued as "Pacific Fleet Tactical Orders & Doctrine (PAC-10)" on 10 June 1943, which was then incorporated in "USF-10A: Current Tactical Orders and Doctrine, United States Fleet" in 1944 which itself was then updated to "USF-10B" effective 1 July 1945. The latter document runs to some 266 pages setting out all aspects of task force (not limited to carrier task forces) command and operation including cruising dispositions both for individual carrier groups but also multi-carrier groups and other formations and for various situations.

How much changed between USF-10A & USF-10B I don't know but the individual carrier group disposition seems to have been pretty much the same from late 1943.

So while you are correct that the USN adopted circular formations against potential air attack the instructions offered a large degree of flexibility to commanders to place the various rings in the best place to operate and meet the threat it was likely to be faced. These are noted as being weak against both surface and dive bomber attack however. Plane guard destroyers for each carrier could only be provided if there were enough available. A submarine threat for example warranted a disposition with width rather than depth. It also needed to take account of the range at which light AA shells would self destruct as well as the number of escorting destroyers available (which increased over time). There were extensive tables setting out how escorts should be disposed to meet certain events. By way of example:-

Cruising Disposition 6-R -"normal carrier force day or night high visibility disposition".
"It is suitable for use of a carrier force for defense against both aircraft and submarines. It permits a rapid shift to cruising disposition 5-V, the air defense disposition. Surface attack not probable"

CV/CVL - 2,500 yard radius from the centre
BB & CA/CL - 4,500 yard radius from the centre
DD - up to 9,000 yards from the centre

Cruising Disposition 5-V - "is an air defense disposition"
"Suitable for use by a carrier force for defense against actual air attack. This is normally formed from 6-R. Upon completion of attack, and additional attacks unlikely, disposition will be changed to 6-R"

The whole TG was then closed up
CV/CVL - 2,000 yard radius
BB & CA/CL and most of the DD (8 of the 12 DD assumed available in the example are in this ring)- spaced around a single ring at a distance determined by the TG commander with a handful (remaining 4) of picket destroyers further out

These are only 2 examples of many set out for different situations and weather conditions many of which do not conform to the concept of concentric rings.

Thumpalumpacus said:

Yeah, I'm getting ready to start rereading Lundstrom's First South Pacific Campaign, this thread has me more interested in IJN capabilities and I need to refresh my knowledge.

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Lundstrom's First Team, V1 and V2 and Black Shoe Carrier Admiral, are crucial reading.

Glider said:

Some context. I served on HMS Tiger and on one of her last live firing AA shoots, she shot the target down with her second 6in shell. The Gunnery officer lost a bet as he said that it would be the first shell.
Pretty impressive

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That is pretty cool! My dad was a gunner on a US navy ship, and was apparently the only guy who could hit the target drone or whatever it was ... and he leveraged that to get away with murder for a while, until they found another guy and transferred him to the ship!

RCAFson said:

Lundstrom's First Team, V1 and V2 and Black Shoe Carrier Admiral, are crucial reading.

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All read already, in rotation for rereading soon.

Also recommend Francillion

Also, check out The Essential Calvin and Hobbes.

SaparotRob said:

Also, check out The Essential Calvin and Hobbes.

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it's so sad that Hobbes didn't survive that last Kamikaze mission ... but of course the big question, what caliber were all those strikes all around his plane precisely?

EwenS said:

Again be careful about "Standard US navy formations".........................

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people should be even more careful about the changes in AA armament, which were often and sometimes legend.
The original Lexington never got any 40mm Bofors guns and never had any 5in/38s.
Every time the Saratoga turned around she was damaged and her armament always seemed to get at least tweaked every time she went into dockyard

Note that distances between ships were also somewhat based on reducing friendly fire incidents so distances took self destruct distances of the light AA into account as well as the 'optimum' coverage of the AA guns.

In July 1943 they were thinking about changing the Saratoga's AA battery as they were not happy with the 20mm guns and wanted more 40mm guns. Since they only had limited experience with 5in proximity fuses (and/or limited amounts them) there was also a proposal to take out 4 of the 5in/38s and replace them with two quad 40mm guns. Saratoga was running into severe weight problems. During this refit/repair which took place from Dec 1943 to Jan 1944, they dropped the number of 20mm guns from 52 to 16. they had 23 quad and two twin 40mm guns. Refit/repair was in Jan 1944.
You can also see a bit overlap between planned refits and latest battle experience. The actual refit took place 5-6 months after the commanding officer made his recommendations.

Shortround6 said:

people should be even more careful about the changes in AA armament, which were often and sometimes legend.
The original Lexington never got any 40mm Bofors guns and never had any 5in/38s.
Every time the Saratoga turned around she was damaged and her armament always seemed to get at least tweaked every time she went into dockyard

Note that distances between ships were also somewhat based on reducing friendly fire incidents so distances took self destruct distances of the light AA into account as well as the 'optimum' coverage of the AA guns.

In July 1943 they were thinking about changing the Saratoga's AA battery as they were not happy with the 20mm guns and wanted more 40mm guns. Since they only had limited experience with 5in proximity fuses (and/or limited amounts them) there was also a proposal to take out 4 of the 5in/38s and replace them with two quad 40mm guns. Saratoga was running into severe weight problems. During this refit/repair which took place from Dec 1943 to Jan 1944, they dropped the number of 20mm guns from 52 to 16. they had 23 quad and two twin 40mm guns. Refit/repair was in Jan 1944.
You can also see a bit overlap between planned refits and latest battle experience. The actual refit took place 5-6 months after the commanding officer made his recommendations.

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And beware of why updates hadn't previous occurred.

Lex and Sara had their light AA improved throughout the period from their completion at the very end of 1927 to Dec 1941. But major modernisation of their AA armament was continually postponed in the late 1930s (when the USN only had 5 carriers).

As for CV-2 Lexington the only work on her 12 5"/25 armament after the outbreak of WW2 was replacement of her worn barrels (that had been done to Sara pre-war). As for her light AA, after her Aug 1941 update, she started the war with 5 quad 1.1" and about 24 single 0.5". When she lost her 8" turrets at Pearl Harbor in March 1942 she got another 7 quad 1.1" and 22 single 20mm and seems to have kept the 0.5". She didn't get 40mm guns because she was lost before the first US twin & quad mounts were available to fit to any ship, as I noted in a previous post.

CV-3 Saratoga was able to get a more extensive update to her AA armament because she was torpedoed in Jan 1942 which put her in dock, and which led to the decision to give her the previously discussed armament modernisation while she was there. (Does that make her a lucky or unlucky ship?) So out went the 8" turrets to be replaced by twin 5"/38 turrets. Then to standardise her armament, the 12 single 5"/25 were replaced with 8 single 5"/38. Then as the 40mm were still not available, the number of 1.1" was increased from 5 to 9 (the extras in place of the lost 5"/25) and 32 single 20mm added. By the time she needed to go into dock again after being torpedoed in Aug 1942, the 1.1" could finally be replaced with quad 40mm and another 20x20mm added. The big upgrade was with the refit that ended in Jan 1944 that you note. And that was pretty much how she remained to the end of the war despite 2 more yard periods.

But this constant upgrade when ships went in for repair/refit was really no different to what went on in other USN ships nor the ships in other navies as more and new weapons became available. Sara just represents a rather extreme example made possible by her sheer physical size.

Just by way of coincidence while Saratoga was receiving the big 1943/44 upgrade so was CV-16 Lexington. On the night of 4/5 Dec 1943 she was torpedoed and repairs took until 20 Feb 1944. She emerged from that with an extra 8 quad 40mm (up from 9 when completed in Feb 1943) for a total of 17 such mounts. She was the first to get this upgrade which was applied to most, but not all, the Essex class as they became became due for refit or arrived in the Pacific. Some of these extra mounts couldn't be fitted until the ships reached the Pacific as otherwise they would have been too wide for the Panama Canal.

Wild_Bill_Kelso said:

Also recommend Francillion

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I think as germane to this topic would be Bloody Shambles, too. I may just order these, thanks for the tips.

Thumpalumpacus said:

I think as germane to this topic would be Bloody Shambles, too. I may just order these, thanks for the tips.

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Yeah i've been trying to get those for a while, every time I have the money the price goes up. It's annoying they are out of print in this era of PoD...

Although not in line with the topic, a friend from a model club had been a rear gunner on SBDs while still in his teens. On the Enterprise, his job during attack was on the flexible mount single 20mm near the deck edge. The only model airplanes I ever saw him build was SBD-5s, both controlline and R/C.

One other thing about upgrades to AAA on US Carriers - given the rate at which they were being sunk and badly damaged by Japanese aircraft, it may be possible to view the scramble to upgrade AAA as something other than the calm light of reasoned analysis, and something more akin to panic. Something needed to change, and that something was really Hellcats. But until then, more defensive guns, whatever is available, will fit, and seems to work even a tiny bit better...

Wild_Bill_Kelso said:

Something needed to change, and that something was really Hellcats. But until then, more defensive guns, whatever is available, will fit, and seems to work even a tiny bit better...

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There were several things that needed to change, the fighters being only one, imo.

Thumpalumpacus said:

There were several things that needed to change, the fighters being only one, imo.

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Yeah agreed of course. Especially for Kamikazes. But overall, I think the Hellcat made a bigger difference to the survival of US CVs than anything else.