Dive Bomber Comparison

[RCAFson]

Hello RCAFson
Quote:"The 5.25 forced two bombers to abort..."

Thanks for that info, IMHO that was an achievement, not that of damaging lightly x planes. IMHO the badly damaged plane, if it was one of those damaged in this occasion, was an achievement.

Quote:"I don't understand, you are arguing that KM AA wasn't hopeless, yet Tirpitz's 4.1in guns had a slower traverse than the RN 5.25in."

Simply because to me the real results are what counts, so 2 out of 12 and effectively prevent accurate torpedodropping was a good achievement.

Quote:"So agree that RN was ahead in AA capability in Oct 1942?"

No, unless you can show that RN AA did better than what USN AA achieved at Santa Cruz

BTW Repulse had 6 4" AA guns and 3x 8 pom-poms IIRC and might well has been able to use it 9-12 x 4" LA guns against VTs

Juha

My point is that Navweaps says that 10/sec traverse is too slow yet Tirpitz was able to use her 4.1in AA effectively. Navweaps opinion on traverse rates is, therefore, wrong.

Most sources state 4 x 4" singles on Repulse. Repulse was fitted with two experimental 4" twin turrets but these were removed prewar and replaced with 4" singles, according to:
World War 2 Cruisers

The RN did better during PQ-18 and Pedestal and did so against heavily armoured Luftwaffe aircraft.

 

[RCAFson]

Hello RCAFson
on that 40deg, now the plan was during the Pedestal that appr 3 DDs were 2000ys out of the heavy ships, other DDs 4000-6000y out. But when ships manouvered wildy under air attacks the distanced changed and sometimes even the outer DDs were much nearer to heavy ships than 4000y. And the 85 deg elevation of US DDs allowed that USN's anti-aircraft formation was that DDs were around heavy ships 2000y out. AND if you look pictures of RN Pacific Fleet under air attack in 1945 you can see that for some reasons the DDs (Ts and Us) were much nearer than 6000y from carriers. Why, for some reason when 55 deg elevation allowed it, also RN DDs operated much closer to carriers than that 4000-6000y.

Juha

Destroyers had to stay outside the self destruct range of 40mm ammo. A destroyer might position itself behind or in front of a carrier to provide a close range barrage.

 

[Juha]

Hello RCAFson
if you read carefully WW2 Cruisers, they gave the right info, 6 4" HA guns for Repulse, and she had 2 HACS.

Quote:" My point is that Navweaps says that 10/sec traverse is too slow yet Tirpitz was able to use her 4.1in AA effectively. Navweaps opinion on traverse rates is, therefore, wrong."

Based on what? I don't know which type of guns shot down those 2 Albacores, 20mm, 37mm or 105mm (4.1") or even 150mm, do you? And after all slow training didn't made it impossible to shoot down a/c it just made it more difficult.

Quote:" The RN did better during PQ-18 and Pedestal and did so against heavily armoured Luftwaffe aircraft"

Have you info on the real LW losses during PQ-18 attack? I have and on no day they were not as bad as was IJNAF's at Santa Cruz.The total number of a/c lost to all causes (incl. those shot down by FAA fighters) during the whole several days attack period (from 13 to 18 Sept 42) was not much more than that USN AA shot down in one day, LW losses during the attacks on PQ 18 were some 28-31 planes. And if we counted also those shot down by F4Fs at Santa Cruz, well.

And can you give me info what heavy armour there was in the nose of He 111. Now He 111 could take more damage than Kate, but not because it was armoured, the armour protected it from fire from behind, but being twin engine plane with good bullet proof fuel tanks. But it was also bigger plane with stricter torpedo dropping parameters. So maybe somewhat more difficult target to AA but not significantly, but for pilot there was only Plexiglas between him and the target.

Juha

 

[Glider]

I did address it. But a 10 deg/sec traverse gun can swing 90 degs in the time it takes a 205 knots aircraft to fly about 1000 yds. This is hardly a serious handicap, and again 10degs/sec is better than most Axis AA guns.

The RN was an "an organisation that specialises in this topic" and they say 10-12 r/m and I believe them.

When I was in the RN I was told that the 3in 120 rpm and it did in trials but 90rpm as the max in real life so I have a certain caution about things like this. Caution based on real life and personal experience. So when I am told that the 5.25 couldn't do the designed 12rpm because of practical problems in real life I believe them.
A clue was in the demonstration detailed when they managed 10rpm in an ideal situation. You never did explain why they didn't manage the 12rpm.

It was becoming apparent by 1942 that the Luftwaffe would be introducing high speed guided missiles while very high speed fighter bombers were also appearing. These trends were not evident when the 5.25in gun was designed, nor was VT ammo, and a 20deg/sec 5.25 mount with VT ammo would be better able to engage very close range, very high speed targets.

So the British wanted to improve the training speed of their AA guns because of guided missiles in 1942, a new idea that I will grant you. You can of course support this statement

 

[RCAFson]

When I was in the RN I was told that the 3in 120 rpm and it did in trials but 90rpm as the max in real life so I have a certain caution about things like this. Caution based on real life and personal experience. So when I am told that the 5.25 couldn't do the designed 12rpm because of practical problems in real life I believe them.
A clue was in the demonstration detailed when they managed 10rpm in an ideal situation. You never did explain why they didn't manage the 12rpm.
So the British wanted to improve the training speed of their AA guns because of guided missiles in 1942, a new idea that I will grant you. You can of course support this statement

I fully agree that one should be skeptical, but in this case we have an RN gunner confirming the stated ROF. I don't undestand why you are fixated on 12 r/m when the reference states 10-12 r/m.

As I explained, this was not an "ideal situation" as the loading tray is at it's most difficult loading angle when the gun was being loaded at low angles of elevation. You can see in this film clip at 3:39 how the 4" twin mount actually has to be elevated to be loaded at low angles:
NARVIK MATERIAL - British Pathe

So you are claiming that the aerial threat didn't evolve during WW2? That is also a "new idea" that I am sure you can support with abundant references?

 

[RCAFson]

Hello RCAFson
if you read carefully WW2 Cruisers, they gave the right info, 6 4" HA guns for Repulse, and she had 2 HACS.

Quote:" My point is that Navweaps says that 10/sec traverse is too slow yet Tirpitz was able to use her 4.1in AA effectively. Navweaps opinion on traverse rates is, therefore, wrong."

Based on what? I don't know which type of guns shot down those 2 Albacores, 20mm, 37mm or 105mm (4.1") or even 150mm, do you? And after all slow training didn't made it impossible to shoot down a/c it just made it more difficult.

Quote:" The RN did better during PQ-18 and Pedestal and did so against heavily armoured Luftwaffe aircraft"

Have you info on the real LW losses during PQ-18 attack? I have and on no day they were not as bad as was IJNAF's at Santa Cruz.The total number of a/c lost to all causes (incl. those shot down by FAA fighters) during the whole several days attack period (from 13 to 18 Sept 42) was not much more than that USN AA shot down in one day, LW losses during the attacks on PQ 18 were some 28-31 planes. And if we counted also those shot down by F4Fs at Santa Cruz, well.

And can you give me info what heavy armour there was in the nose of He 111. Now He 111 could take more damage than Kate, but not because it was armoured, the armour protected it from fire from behind, but being twin engine plane with good bullet proof fuel tanks. But it was also bigger plane with stricter torpedo dropping parameters. So maybe somewhat more difficult target to AA but not significantly, but for pilot there was only Plexiglas between him and the target.

Juha

I am sorry but I read the info on WW2 Cruisers again and it states that Repulse had her two twin 4" experimental turrets replaced by 2 single 4" before the war began, leaving her with 4 4" HA guns.

Maybe you could provide your figures for PQ-18? The other thing to remember is that attacks on a convoy do not have a central focus, and so the AA coverage has to be spread wider and the enemy can make multiple attacks on multiple targets at the same time. Against a carrier task force, the carrier becomes the central focus of the attack and the defence can concentrate accordingly.

Look, it is painfully obvious that even 8/degs second of training is quite sufficient for most WW2 aerial targets. I have a feeling that if navweaps said the world is flat, that I would have to prove otherwise...

AA fire involves time fuzed shells bursting around the target, with close range weapon also enaging from in front, below and behind, and armour and self sealing tanks will help reduce losses, or are you now going to argue that armour and self sealing tanks were a waste of time?

 

[Glider]

I fully agree that one should be skeptical, but in this case we have an RN gunner confirming the stated ROF. I don't undestand why you are fixated on 12 r/m when the reference states 10-12 r/m.

As I explained, this was not an "ideal situation" as the loading tray is at it's most difficult loading angle when the gun was being loaded at low angles of elevation. You can see in this film clip at 3:39 how the 4" twin mount actually has to be elevated to be loaded at low angles:
NARVIK MATERIAL - British Pathe

So you are claiming that the aerial threat didn't evolve during WW2? That is also a "new idea" that I am sure you can support with abundant references?

Because in the real world the 5.25 was seen as a dissappointment in the AA role. Why when you are being questioned about the 5.25 do you present a clip of the 4in totally different in every way as a type of support?
Of course the threat developed, mainly in the numbers used, not individual speed, but the idea that the RN developed their weapons because of guided missiles in 1942 is a joke that does you no credit and only make you look foolish. You cannot possibly support that statement.

 

[Juha]

Hello RCAFson
maybe a third try, 2 LA 4" and 2 3" HA replaced by 4 4" HA, then 2 twin BD turrets put in but removed later (in fact because PoW went to an official visit to Canada and needed suitable suits and a pool and not put back when Repulse returned in UK) and replaced by 2 single 4" HA. You can see the HA guns in photos, first pair was on main deck just front of the boats, second pair abreast the second funnel high up and those which replaced the BD turrets abreast the main mast on one deck above the main deck.

I gave the figures, I don't bother be more precise because most of planes are said "went missing near Spitsbergen, went missing after forced landing into sea etc", on some mentioned "shot down by the AA of PQ-18", on few "shot down by a fighter", I also incl those which crashed on landing while returning from combat mission, if damage was 60% or more.

As I wrote bullet proof fuel tanks increased survivability but armour, which increased significantly survivability against attacks by .303 mgs armed Sea Hurricanes, there was a heated after action debate on this because amongst the cargo of the merchantmen of PQ-18 there were cannon armed Hurricanes, hasn't so much effect because most of the AA became from frontal sector and from airburst most of the splinters go forward

Juha

 

[RCAFson]

Because in the real world the 5.25 was seen as a dissappointment in the AA role. Why when you are being questioned about the 5.25 do you present a clip of the 4in totally different in every way as a type of support?
Of course the threat developed, mainly in the numbers used, not individual speed, but the idea that the RN developed their weapons because of guided missiles in 1942 is a joke that does you no credit and only make you look foolish. You cannot possibly support that statement.

I read through the despatches here:

Loss of Force Z:
http://www.ibiblio.org/hyperwar/UN/UK/LondonGazette/38214.pdf

Battle of Crete:
http://www.ibiblio.org/hyperwar/UN/UK/LondonGazette/38296.pdf

Mediterranean convoys:
http://www.ibiblio.org/hyperwar/UN/UK/LondonGazette/38377.pdf

and I can't find any criticism of the 5.25 gun.

I showed you an example of how the height of the breech makes a HA gun more difficult to load at low elevations. The breech in the 5.25 is at maximum height at close range, and the loader will have to lift the 80lb round higher than when engaging HA targets.

The RN continued to develop new weapons and improve older ones to meet an evolving threat. The USN began guided missile development pre-war and work on the Bat GM in Jan 1941:
Bat (guided bomb) - Wikipedia, the free encyclopedia
Howeth: Chapter XL (1963)
and the RN would have apprised of these developments and the need to defend against them. The development of VT ammo gave guns the ability to defend against these weapons even at very close ranges, where target bearing would increase rapidly, and of course the UK had an active jet aircraft research program.

Warship 2007, p11. The RN was working on guided projectiles prewar (of course it was obvious even then that Queen Bee could be used as a weapon) and the UK was working on beam riding weapons during the war.

So the idea that guns would need to deal with high speed robot "kamikaze" weapons was hardly new. The Allied intelligence services kept close track of Nazi missile development, and the RAF even launched a massive raid on an island called Peenemünde...maybe you've heard of it?
Bombing of Peenemünde in World War II - Wikipedia, the free encyclopedia

However, we are certainly getting off topic here. I think I've built a pretty good case for the RN being ahead of the USN in AA in Oct 1942, but of course by Jan the USN was introducing the VT round and mass producing the 40mm gun, so by early 1943 the USN must have overtaken the RN.

 

[RCAFson]

Hello RCAFson
maybe a third try, 2 LA 4" and 2 3" HA replaced by 4 4" HA, then 2 twin BD turrets put in but removed later (in fact because PoW went to an official visit to Canada and needed suitable suits and a pool and not put back when Repulse returned in UK) and replaced by 2 single 4" HA. You can see the HA guns in photos, first pair was on main deck just front of the boats, second pair abreast the second funnel high up and those which replaced the BD turrets abreast the main mast on one deck above the main deck.

I gave the figures, I don't bother be more precise because most of planes are said "went missing near Spitsbergen, went missing after forced landing into sea etc", on some mentioned "shot down by the AA of PQ-18", on few "shot down by a fighter", I also incl those which crashed on landing while returning from combat mission, if damage was 60% or more.

As I wrote bullet proof fuel tanks increased survivability but armour, which increased significantly survivability against attacks by .303 mgs armed Sea Hurricanes, there was a heated after action debate on this because amongst the cargo of the merchantmen of PQ-18 there were cannon armed Hurricanes, hasn't so much effect because most of the AA became from frontal sector and from airburst most of the splinters go forward

Juha

OK, I think you are correct about 6 4in HA guns on Repulse. I found a line drawing of her in 1940 and it does show 3 4in HA guns per side:
http://www.kbismarck.com/repulse40.gif

IIRC, the Hurricane pilots did not make many claims during the PQ-18 operation, so that leaves most of the kills to the AA guns.

 

[Freebird]

I think its worth mentioning that the HACS worked to some degree over Force Z despite the problems. If I remember correctly a high proportion of the high level bombers were damaged and had to abandon the original plan for them to attack twice.
Could be wrong on this but its something that I recall

The account i have says that all of the Nell bombers were hit by HA AAA in the first attack, but still released bombs. However neither Repulse or PoW had any critical bomb damage.

This discussion is about AA capability.

Strange, for some reason i thoght this thread was about Dive bombers.

 

[parsifal]

My opinion is that we should try and reach some consensus and then move back on topic.

I think that RN AA was effective, but I would never say it was the best. The RN had its share of problems, but it was still quite useful and effective. It had quite good success against divebombers.

Hopefully we can start to move back closer to the discussion topic

 

[Juha]

Hello RCAFson

Quote:" IIRC, the Hurricane pilots did not make many claims during the PQ-18 operation, so that leaves most of the kills to the AA guns."

Yes, only 3 Ju 88A-4s from 8. and 9./KG 26 definitely shot down by fighters on 14 Sept. Few more of the missing a/c might well have been succumbed to fighter attacks but definitely the AA was the major killer.

On HMS Repulse, just for the record, I mixed two things, Repulse transported the PoW to South Africa and South America in 1925. But the twin 4" BD turrets were removed because of the planned trip of King and Queen to Canada in 1939.

Juha

 

[Nikademus]

My opinion is that we should try and reach some consensus and then move back on topic.

I think that RN AA was effective, but I would never say it was the best. The RN had its share of problems, but it was still quite useful and effective. It had quite good success against divebombers.

Hopefully we can start to move back closer to the discussion topic

I would second that. Comparing the losses for Santa Cruz and PQ-18 in particular is a slippery slope. Conditions were very different. All and all the RN escort (largely DD's) managed a good fight, dealing very heavy losses to the Luftwaffe crews against a swarming attack on a large convoy of 40 merchants.

 

[Shortround6]

I think I've built a pretty good case for the RN being ahead of the USN in AA in Oct 1942, but of course by Jan the USN was introducing the VT round and mass producing the 40mm gun, so by early 1943 the USN must have overtaken the RN.

No, you haven't.
You have built a good case that the RN had more 40mm pom-pom barrels mounted than the US had 1.1in barrels mounted and you have shown that the RN may have had more even lighter AA mounted.
You have not shown that RN was actually ahead of of the US in larger DP guns, either in barrels mounted or capability of those barrels.
You have not shown that the RN was ahead in fire control, that is that their directors PERFORMED better than the US directors.
Radar is a sensor, it can feed more accurate information to a director than an optical sight/device can but if the director and or system of getting aiming information to the guns is defective or performs poorly the radar alone may not be able to make up the difference.
Many countries were working on advanced AA mountings for ships and advanced ideas for directors. The problem was turning the ideas into actual working hardware that would work and CONTINUE to work at sea. Another problem was that many of these "ideas" were tried one at a time instead of in combination or were tried too many at a time and so failed to keep working when needed.
The Germans who you seem to claim were so far behind not only had tri-axial stabilized mountings for their twin 8.8 and 10.5 cm guns but had a tri axial stabilized mounting for their twin 37mm AA guns. They paid a penalty in that the big gun mounts weighed as much as a British low angle twin 12cm mount. THE 37mm was let down by the fact that the guns were not automatic but were miniature big guns. Each round had to be hand loaded. There were also maintenance and reliability issues with both mounts, but the "idea" was advanced. The 37mm mount was also heavy and hand powered.
The Italians had a quad stabilized 90mm mounting but again it was stretching what was possible too far. And, again, sophistication has a price. Was 19 tons too much to pay for a single 3.5" AA gun no matter how sophisticated the mount? They were also working on RPC. Some Italian destroyers had both a pair of 40mm pom-pom guns and a pair of 13mm MG mounts, not either/or like too many British destroyers.
The British were certainly aware that the Japanese destroyers had main guns with high elevation, they may not have known the rate of fire or loading angle problems.

The cost associated with good AA defense was not the cost of the guns themselves, or even in some cases the mounts, but the cost of the increased size of the ship needed to carry the AA armament. For every ton of armament weight you need several tons of ship to support it and for every foot in hight above the water you need either ballast weight or a larger hull to maintain stability. Adding several tons of "improved" AA director on top of the bridge can call for extreme weight savings in other areas or a new hull in future classes. With destroyer tonnage limited by treaty Navy's had to accept limits on capabilities or limits on numbers.

The RN's .5in MG mount was an overweight piece that provided little firepower for the space and weight it took up. Awkward to use, it might have been a viable weapon in 1930 or so but by 1939 it was of little use. The tonnage may have been better used by free swinging mounts like the US was using on it's .50cals or the Germans were using on their 20mm guns even if they weren't the equal of the later Oerlikon

 

[Glider]

However, we are certainly getting off topic here. I think I've built a pretty good case for the RN being ahead of the USN in AA in Oct 1942, but of course by Jan the USN was introducing the VT round and mass producing the 40mm gun, so by early 1943 the USN must have overtaken the RN.

Interestingly I do agree with this comment. We disagree on the 5.25 but this summary I do go with. However it is to simplistic. My own summary would split the HAA and LAA.

HAA
There is no doubt in my mind that the 5in L38 was the best all round destroyer gun of the war and far more effective than those fitted to British destroyers. That said the RN twin 4in, twin 4.5 were good guns so the difference wasn't that great when Cruisers and Capital ships were taking on aircraft and the 5.25 could be effective depending on conditions.
note - I don't include the 4.5 carried on destroyers in this section. They would have been ok against torpedo bombers but nothing at altitude.

However we are talking about September 1942 and without the VT fuze the potential for the 5in L38 was significantly reduced.

LAA
On this in 1942 I believe that the RN had an advantage with the exception of the few USN ships fitted with the 40mm which was just entering service. Almost every british destroyer had a quad 2pd and 6 - 8 20mm, some had more some less but this is a fair summary. Cruisers and heavier ships carried more.

The problem that the USN had was that they were more or less limited to the 1.1 in one of the most dissapointing weapons used by the USN, the 0.5 mg which lacked firepower and the 20mm which was effective but on the small side. As mentioned earlier those few ships with the 40mm had a clear advantage.
The Bristol class destroyer in production up till 1942 had as their initial war changes the loss of a set of torpedos for 4 x 20mm and then the quad 1.1in removed for another 2 x 20mm. Even the first Fletcher class DD's which entered service in 1942 had a quad 1.1in and 6 x 20mm arguably less effective than the LAA carried on the RN destroyers.

 

[renrich]

SR, very nice post, logical and informative. All the AA and radar that was added to ships in WW2 also required crew to man them and spaces to house the added crew and supplies to feed them. The ships got crowded and top heavy. CA25 of the USN stopped in Hawaii and exchanged two scout planes for two twin mount 40 mms but that does not sound like the trade was weight for weight.

 

[RCAFson]

No, you haven't.
You have built a good case that the RN had more 40mm pom-pom barrels mounted than the US had 1.1in barrels mounted and you have shown that the RN may have had more even lighter AA mounted.
You have not shown that RN was actually ahead of of the US in larger DP guns, either in barrels mounted or capability of those barrels.
You have not shown that the RN was ahead in fire control, that is that their directors PERFORMED better than the US directors.
Radar is a sensor, it can feed more accurate information to a director than an optical sight/device can but if the director and or system of getting aiming information to the guns is defective or performs poorly the radar alone may not be able to make up the difference.
Many countries were working on advanced AA mountings for ships and advanced ideas for directors. The problem was turning the ideas into actual working hardware that would work and CONTINUE to work at sea. Another problem was that many of these "ideas" were tried one at a time instead of in combination or were tried too many at a time and so failed to keep working when needed.
The Germans who you seem to claim were so far behind not only had tri-axial stabilized mountings for their twin 8.8 and 10.5 cm guns but had a tri axial stabilized mounting for their twin 37mm AA guns. They paid a penalty in that the big gun mounts weighed as much as a British low angle twin 12cm mount. THE 37mm was let down by the fact that the guns were not automatic but were miniature big guns. Each round had to be hand loaded. There were also maintenance and reliability issues with both mounts, but the "idea" was advanced. The 37mm mount was also heavy and hand powered.
The Italians had a quad stabilized 90mm mounting but again it was stretching what was possible too far. And, again, sophistication has a price. Was 19 tons too much to pay for a single 3.5" AA gun no matter how sophisticated the mount? They were also working on RPC. Some Italian destroyers had both a pair of 40mm pom-pom guns and a pair of 13mm MG mounts, not either/or like too many British destroyers.
The British were certainly aware that the Japanese destroyers had main guns with high elevation, they may not have known the rate of fire or loading angle problems.

The cost associated with good AA defense was not the cost of the guns themselves, or even in some cases the mounts, but the cost of the increased size of the ship needed to carry the AA armament. For every ton of armament weight you need several tons of ship to support it and for every foot in hight above the water you need either ballast weight or a larger hull to maintain stability. Adding several tons of "improved" AA director on top of the bridge can call for extreme weight savings in other areas or a new hull in future classes. With destroyer tonnage limited by treaty Navy's had to accept limits on capabilities or limits on numbers.

The RN's .5in MG mount was an overweight piece that provided little firepower for the space and weight it took up. Awkward to use, it might have been a viable weapon in 1930 or so but by 1939 it was of little use. The tonnage may have been better used by free swinging mounts like the US was using on it's .50cals or the Germans were using on their 20mm guns even if they weren't the equal of the later Oerlikon

I don't want to continue to drag this this thread OT, but...

RN AA proved that it was effective in the Med and in the Arctic. Even over Dunkirk, the RN claimed 35 kills using their prewar AA fit including the much maligned quad .5" and the RN did not seem to make greatly inflated AA claims, as in some other navies (Off Crete, they claimed 22 and probably got close to that number and during Pedestal they claimed 66 from fighters and guns and got 42). The RN's AA FC was vastly improved by Oct 1942 over what it was in 1940 or early 1941, both in quantity in terms of number of AAA and quality, in terms of FC. The RN still had a lead over the USN in OCT 1942 in numbers of DP guns carried and in AAA, when the calibre is considered, although overall AAA numbers had equalized. The RN had advanced tachymetric directors with radar controlling most pom-pom mountings on cruisers and larger, while the same ships also had AA FC radars with gyro tachymetric directors for their DP guns. USN DP guns had been largely ineffective prior to Santa Cruz and even at Santa Cruz it seems likely that the 20mm guns were the big killers, and the 40mm bofors was still a very scarce item as was the Mk51 gyro director for bofors.

The KM did not provide director control for any AAA mountings, and neither Bismarck's nor Tirpitz had a stellar record against aircraft, with Bismarck being unable to make a single kill. Neither the KM, Italian navy, nor the IJN ever developed AA FC radar or provided their close range weapons with gyro based tachymetric AA directors.

In the Pacific, Force Z matched the USN, in numbers ofAA kills for the USN's first 3 major carrier battles, which featured massed defence by the USN's best ships, while Force Z had to make do with 3 destroyers with no AA FC and an elderly battlecruiser that barely matched a modern RN light cruiser in AA capability, and even Prince of Wales was having major equipment problems. Given equal numbers of equivalent ships it seems likely that the RN could have exceeded the USN's AA kill rate at Santa Cruz because the tachymetric radar controled pom-pom was a more effective weapon than that carried on the USN ships, save for the quad bofors which were still rare. If the quad 1.1" was effective it didn't show it at Eastern Solomons where it was available in quantity on both Enterprise and USS North Carolina which were the focus of the attack. In that action the USN claimed 28 AA kills and got 5 (including an F4F).

I agree fully with your 2nd to last paragraph and in light of the poor record of USN DP guns on destroyers, the RN decision to forgo a HA DP main armament in favour of 40 deg elevation but with the addition of a quad pom-pom, seems like the the correct decision, although it probably didn't seem so at the time, especially in light of the USN's wild over claiming in 1942.

Regarding the quad .5", I agree that it was ineffective in a relative sense, but simple logic tells me that a Ju-88 or He-111 that strayed too close to a quad .5" mount, would feel some major pain if the mounting even got on target for 1 second. It must also have deterred strafing attacks where the quad .5" would be presented with a low deflection shot, and could stay on the target more easily.

 

[Shortround6]

Almost every british destroyer had a quad 2pd and 6 - 8 20mm, some had more some less but this is a fair summary.

There were 85 British destroyers built after 1925 that did not have quad pom-pom guns. 'A' to 'I' classes. 45 of them were sunk or out of action by the end of 1942. Including the Tribals going on to the 'N' class adds another 56 destroyers. Just under 40% had the quad 2pd and the percentage is only that high if you don't count any of the WW I veterans. of the 40 destroyers of the Tribal and 'J', 'K' and L classes 27 of them were sunk or permanently out of action by the end of 1942.
This is from all causes, gunfire, torpedo, mine and air attack. There is no doubt that they ALL were hard worked and did more than their share in gaining victory. There is also little doubt that more of their crews might have returned home if they had had better AA armament.

The problem that the USN had was that they were more or less limited to the 1.1 in one of the most dissapointing weapons used by the USN, the 0.5 mg which lacked firepower and the 20mm which was effective but on the small side....... Even the first Fletcher class DD's which entered service in 1942 had a quad 1.1in and 6 x 20mm arguably less effective than the LAA carried on the RN destroyers.

The 1.1 is an interesting story in the best being the enemy of good, complications that sound good but don't work out and good intentions.
It was specifically designed to be an anti-dive bomber gun (how about that, we are somewhat back on track and was the smallest caliber that could be made to use a 1lb high explosive projectile and so meet the requirements of the St. Petersburg treaty that banned exploding bullets. Work was started in 1930 when such things were still considered to be important. Rate of fire was slowly improved to the point where they got 140 rpm from one barrel so a quad mount was decided upon to "equal" the rate of fire of a single .50 cal MG. Granted each hit would be much more devastating. In order to deal with dive bombers (of which the US Navy was experimenting with in 1930) the mount was given 110 degrees of elevation to compensate for roll and such when the target is coming STRAIGHT down. Because normal traverse was of little use in such situations it was also arranged so that the barrels could pivot or swing 30 degrees to either side of the dead center position without the entire mount traversing. Naturally such refinements added size and weight to the mount. This being the best being the enemy... In practice the extra traverse was either locked out or eliminated but too late to save weight. The 10 degree elevation might not have been needed in practice either. The 1.1 was a fairly powerful round for it's caliber with more recoil than the mount could stand up to initially and it had to be beefed up. While it did have tracer unlike early British 2pdr ammunition it did not have a self destruct and so didn't make those little puff balls of smoke several thousand yds out to deter attacking aircraft.
In the end it would up being overweight for the firepower it offered, like many other early weapons/mounts in the 20mm to 40mm range.

 

[Glider]

SR, very nice post, logical and informative. All the AA and radar that was added to ships in WW2 also required crew to man them and spaces to house the added crew and supplies to feed them. The ships got crowded and top heavy. CA25 of the USN stopped in Hawaii and exchanged two scout planes for two twin mount 40 mms but that does not sound like the trade was weight for weight.

I thin its worth remembering that generally the USN ships were top heavy to begin with and any addition needed serious changes.

There has been some discusson about the RN quad 0.5 but by the period we are talking about these had been replace by 20mm guns and shouldn't really be taken into account.