What was the most effective naval anti-aircraft gun of WW2?

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by lwd » Fri Nov 20, 2009 7:01 pm

One that hasn't been mentioned is the Japanese 3.9" gun. My impression is that it had a lot of potential. Indeed if coupled with a radar fire control and proximaty rounds it might have been better than the 5"38.

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by dunmunro » Fri Nov 20, 2009 8:01 pm

Bgile wrote:I think there is a fairly good summary on navweaps.com. The twin mounts were redesigned for use on Vanguard so probably didn't have as many problems. One criticism was the shell weight being possibly too heavy for one man to have to handle. I know the manually loaded 5"/54 guns intended for Montana and used on the Midway class carriers were unpopular for that reason.

The pom pom had low muzzle velocity, giving it a substandard effective range compared to the 40mm Bofors.
Unfortunately the Navweaps article is hopelessly dependent on secondary sources, and information regarding the rate of fire is pure conjecture and has no basis in fact. Many other hand loaded weapons used heavier rounds than the 5.25 while also achieving high rates of fire, for long periods of time. Burly loaders tended to be fairly easy to find.

The maximum range of the pom-pom and the bofors were determined by the limits of optical sights when in local control and by the fact the both 40mm rounds were self destructing at about the same range of 3000-4000 yds:

The "Maximum Effective Ranges" of close range weapons are as follows:-
2-pdr. multiple Pom-Pom and Bofors in local control 1,700 yards.
Oerlikon 20 mm. single gun 1,000 yards.
0.5 in. Machine gun. 800 yards.
0.303 in. and 0.30 in. weapons 400 yards.

http://hnsa.org/doc/br224/part4.htm#par473 (paragraph 470 for above data)

The difference in time of flight between the 2850fps bofors and 2400fps Vickers round, doesn't seem to be that substantial over these short distances. I suspect that there was a lot of older pom-pom mounts in service in the RN and these mounts biased opinion against the pom-pom, as given equal FC there shouldn't be a huge disparity in accuracy.

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by dunmunro » Fri Nov 20, 2009 8:03 pm

lwd wrote:One that hasn't been mentioned is the Japanese 3.9" gun. My impression is that it had a lot of potential. Indeed if coupled with a radar fire control and proximaty rounds it might have been better than the 5"38.
IIRC, it only fired a 28lb round and would have had a fairly small lethal burst radius, compared to the 55lb 5"/38 round.

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by hammy » Sat Nov 21, 2009 5:53 pm

With regard to the British Pom-Pom , this weapon had a very long history , starting life among the first of the machine guns in the late 1890s.

You are all familiar with the classic Maxim machine gun with the cylyndrical water jacket around the barrel , and its Vickers 1912, Maxim "Spandau"1908 , and Russian Maxim 1910 derivatives .
Those were all rifle calibre weapons "Lightened" from the original weapon for use by Infantry , but the gun from which they were derived was a heavier weapon on a horse/mule drawn two wheeled artillery mounting ,
( the same tactical thinking behind the Gatling on it's Field Carriage )
and it was made in a number of different calibres , and used as an artillery weapon with the same range as the then very long rifle range of 1500 yards or so .
They made their major combat debut in the war in South Africa ( Boer Wars ) following some experimental use in the Sudan campaigns
( ... against fundamentalist Muslim fanatics led by a charismatic leader ...... erm ...... lessons will be learned ? ? ? )

The Royal Navy , among others , saw that , in it's standard Infantry guise , the gun would be a useful addition to the Marine "landing force" carried by every ship above the smallest of light cruisers , and promptly adopted it for that use . It was also realised that , in the heavier calibres of 40mm , the gun could be used to beat off attacks by the early torpedo boats , at that time (1900 or so ) very lightly built 25knot ( in smooth water ) overgrown steam launches with primitive short range torpedoes , and a few Pop-guns .
As the torpedo boat and it's main weapon were developing very quickly in the period leading up to WW1 they grew in size and so progressively bigger guns were fitted to counter them ; - - 47mm ( 3pdr ) , 57mm ( 6pdr ) , 75/76mm = 3 inch ( 12pdr ) (Dreadnought) , 4 inch ( 35pdr ) , 4.7 inch ( 50pdr ) , at which point the gunners gave up and just fitted the maximum number of 6 inch guns into the battleships secondary battery and gave that the job of fighting off the enemy destroyers and their torpedoes . After all , battleship engagement ranges had increased out beyond the secondary battery's effective range , so these weapons were essentially now redundant ( their previous envisaged use was to "smother" your opponents upperworks while your big guns did the heavy penetrative damage )
Having persuaded the politicians to buy you a lot of very expensive weaponry , it is bad tactics to turn round and tell them that these are now obsolete scrap metal within a couple of years , and so the natural instinct is to put them in store and try to find another use for them .

In the case of the 47mm gun , no real good use could be found , and so they are still being used up TODAY on Royal Naval warships , firing a reduced blank charge as saluting guns . And if you ever wonder why they are on a peculiar little knee high , pyramidal angle iron mounting frame which is bolted onto the deck , that is because the mount was originally made to sit on top of the little round helmsmans conning tower ( like captain Nemo on his "Nautilus" ) that stuck up out of the deck of a 1905 era steam torpedo-boat ! Yes , really .
Quite why , in the year 2010 , with Defence spending cut to the bone , and patients laying on trolleys in NHS hospital wards for the lack of beds to treat them in , we can find money ( and waste deck space ) on redundant ceremonial cac , I dont know . Doubtless our two new Jumbo carriers will carry a battery of them too somewhere .
Makes you proud to be British !

I digress .
A lot of the other surplus guns were reused elsewhere in WW1 , including as extemporised artillery by the army .
Germany did this too , and a lot of what was useless old junk at sea found a new lease of life in the siege conditions of trench warfare , where weight , unwieldiness and tardiness in bringing into action / removal from the scene had diminished in tactical importance . ( Another lesson that could be used by the lads sitting in the forts in Iraq/Afghanistan - I shouldnt like to be a mujahadeen knowing that taking a pop at a distant blur would be rewarded by a 4.5 or 5 inch 60lb response at almost zero trajectory )

Back in WW1 the aeroplane had progressed from the fragile early unarmed scouting machines of 1914 to more workmanlike artillery spotters by late 1915 .
The army wanted AA guns to push these away , and what came out of store to assist were the pom-poms , still in the single barrel pattern , although by now on a pedestal mount that could be bolted down to a truck-bed or a ships deck , to give 360degree coverage .
The navy also started to fit them to warships to cope with the new air threat , and by the war's end anything bigger than a destroyer carried one or more , although these are quite often not listed as part of the armament in bigger ships , presumably because they were regarded as temporary fittings .

As an overgrown belt-fed machine gun , the ammunition was in the Box-on-the-Right set-up that is familiar to us today , and so it was not possible to easily mount two of the barrels side by side .
( you would have to "hand" the mechanism of the one on the left -- not simply done as the Vickers innards are fairly complex ) .
The first twin barrel Pom-Pom to appear post-WW1 carried the barrels above and below a sort of "wheel" arrangement .
This is the same solution you see for the WW2 twin Breda AA Italian naval guns .
( Hotchkiss derived , a steel clip holding the 20-30 rounds proceeds from left to right through the breech area as the gun is fired )

Next to appear was the four barrelled Pom-Pom mount ,( the handing of the left hand barrels had now been achieved ) with the conical muzzle flash deflectors to project the hot gas and burnt propellant grains away from the guns crew . The final variation was the big eightbarreled version .

The army meanwhile had , by the late 1930s , recognised that their single barrel weapon was not up to the new aircraft it would be up against , and had bought the Bofors single barrel gun instead .

The navy have been criticised for sticking with the older Pom-Pom , but you have to bear in mind that the Bofors could not throw an equivalent mass of shells into the sky , except when replacing the remaining shipboard single mounts -- by then pretty much all in destroyers -- very difficult small swift manoeuverable targets to hit from the air unless you got really in close -- in which case the Pom-Pom was still effective !
As a Foreign design , both gun and ammunition would be expensive as license fees would have to be paid , at a period of severe financial constraint .
The Bofors required more space , and was heavier ( warships were very weight-critical then as a result of treaty restrictions ) and the 40mm ammunition was not the same as the 40mm Pom-Pom rounds , a futher headache for the Gunnery suppy chain .

A few Bofors were shipped in the Mediterranean in single mounts , but the weapon only became more common in twin and quad mounts towards the end of WW2 . At the very end , and post-war , the British developed a six barreled Bofors derived AA gun mount , but I dont know that this was successful , or really tried in action . Expensive business , letting one of those off for fun , hmm ?

We seem to have gone full circle now with the 20mm Phoenix Gatling gun ( Goalpost ? ) . Throw enough metal into the air in that direction and you will destroy the target ( or spoil his day ! )

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
To see the real guns ; -There is A Boer war vintage Pom-Pom on an army field carriage in a South African war Memorial Park in Plymouth , Devon . I think that it is a 0.50 calibre , but its 45 years since I was there . Phone Plymouth city council , their Parks and Gardens guys should be able to tell you how to find it .
A Single barreled WW2 era 40mm Pom-Pom is on the terrace outside the Greek War museum in Athens , along with a load of other interesting stuff .
You can see the makers nameplate still -- George Roby Ltd , Coventry ( I think ) . Across the road is the prodigiously fortified glass tower wherein cower the staff of the British Embassy , where the guards glower at you . ...... There is some corner of a foreign field ....... hmm.... .

While in Athens , take the subway train down to Pireaus . Look around Great harbour and all the ferries ; just outside the harbour is where Salamis was fought .Go to the Naval museum - 20 minutes stroll away -- Loads of hardware , big models and other goodies . Afterwards take a stroll around Zeas marina and beyond to mikrolimano and smile at the rich people .
Carry on walking with the sea on your right , that is Phaleron bay where the galleys used to sit in their shelters .
Go on through the park past the new huge Stadium of Peace and Friendship and find the new tramstop just outside .
Take the tram south around phaleron bay and get off at Flisvos marina . Look for a big grey tripod mast and walk to it . That is the Greek Naval Museum , only a couple of Euro to go in , centrepeice is the 1910 Armoured cruiser "George Averoff" -- FASCINATING , and you are left alone in her to poke about deep in the bowels and in the un-restored and unlit bits to a surprising degree -- DO take a good torch .
Also there is a 4 gun Fletcher class destroyer ( now " AETOS " ) with the late-war 3 x twin 3 inch AA , 1 x 5tube tt mount and one DC rack remaining and scars on the deck where the K guns used to be .
The reproduced wooden trireme "Olympias" is there too , unique . All the museums close about 13.30 hrs , so there is about four or five days worth there .
EasyJet from Luton about £130 return . Fancy a trip ?
" Relax ! No-one else is going to be fool enough to be sailing about in this fog ."

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by dunmunro » Sat Nov 21, 2009 8:43 pm

Thanks for the interesting essay! However, I should point out that the octuple pom-pom came before the quad. The quad was specially designed to be light enough to fit onto a DD.

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Re: SoDaK at Santa Cruz

Post by dunmunro » Sun Nov 22, 2009 12:01 am

dunmunro wrote:South Dakota has been credited with 20+ AA kills at the Battle of Santa Cruz. Here is her ammo expenditure and Captain Gatch's assessment of the relative effectiveness of the different weapons:

From South Dakota's Action Report:

Rounds fired:

5" = 890
40mm =4000
1.1" = 3000
20mm = 52000

Captain Gatch's assessment of SoDak's relative AA effectiveness (proportion of kill claims):

20mm = 65%
40mm/1.1" = 30%
5" = 5%

Extracts of SoDak's Action Report were included in AntiAircraft Action Summary, July 1942 to Dec 1942 (Information Bulletin No. 22)
I believe "Showboat" was an affectionate term for USS North Carolina.
Speaking of North Carolina, here's some info regarding her 5"/38 performance during the Eastern Solomons, which is taken from her Captain's action report:
"The battery performance of the 5"/38 battery was excellent. A total of 841 rounds were fired. Dead time was set at 3 seconds. This low value of dead time was set only after training in the war zone. It is estimated that the rate of fire exceeded 17 rounds per gun per minute on all guns. In no case was fire delayed because of ammunition supply. There was no delay in ready service replacements during action and no cease firing.

The last 25 cartridges fired by the right gun of mount 2 contained lead foil. This was the only gun which would not pass the bore gauge after firing, indicating that as a decoppering agent lead foil was not successful. Pieces of lead foil severe found about the desk after firing."

AntiAircraft Action Summary, July 1942 to Dec 1942 (Information Bulletin No. 22)

NC claimed a number of 5" kills but most accounts of the battle seem to indicate that more likely, she got one or two.

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by hammy » Sun Nov 22, 2009 12:30 pm

Sorry for the "essay" length ! I'm an old man , and I do chunter on .

An interesting candidate for the prize for WORST AA gun of the war might be the twin 8 inch , as fitted in all the County class cruisers , including Norfolk and Suffolk , and the later mini two , Exeter and York . Those mountings were given 80 degree elevation for use in the AA role . Has anyone read anything about them actually being used for that ? Must have had a hell of a recoil/recuperator system fitted !
" Relax ! No-one else is going to be fool enough to be sailing about in this fog ."

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by RF » Mon Nov 23, 2009 8:41 am

I haven't heard of the County class 8 inch being used in an AA role before. Presumably they were not of much use to Cornwall and Dorsetshire when they were sunk by Japanese planes......
''Give me a Ping and one Ping only'' - Sean Connery.

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by dunmunro » Mon Nov 23, 2009 11:23 am

"Rather a peculiar characteristic of the suicide Jap is the fact that even though he is determined to end his life by crashing on the ships, he doesn't like hot steel coming at him. We put up the fiercest and most accurate barrage of control fire of any ship here because of our capability to fire main armament at aircraft, and the belch of flame and smoke as the 8" fire and the detonating effect of the shell as they explode near a plane must have given rise to some speculation on the Japanese Home Front. The Tokyo Radio has been heard to broadcast that the two Australian cruisers have a secret weapon which throws forth flame which plucks planes out of the sky. This gives rise to speculation on board that they are out to get us if possible.

The "Aussie" (HMS Australia-dm) does not use her 8" against aircraft, having no Barrage Directors (ABU a radar controlled AA director for main armament-dm) , and in this operation alone 5 planes have suicided into her, as well as some near misses, while a greater number have had a go at us."


http://www.ahoy.tk-jk.net/GentlemansCor ... -capt.html

"Within a week or so our newly acquired gift, H.M.S. Shropshire, entered port and was dry docked. The old crew was dispatched and gradually we Aussies took over and shifted on board. For the next ten months the dockyard fitted us on board with every modern piece of the latest equipment which was available. There was the very latest in Radar which, later on in the War against Japan in the Philippines, the Shropshire was accredited with 92% of reports of enemy aircraft approaching. We were fitted with barrage directors which enabled the 8" guns to be used as anti aircraft guns, and many small A.A. guns were fitted at convenient places"

http://www.ahoy.tk-jk.net/GentlemansCor ... nery..html

RN cruisers began using 6" guns for barrage fire in 1941, and the RN developed a special radar controlled director for main armament guns, called the Auto Barrage Director, or ABU and was fitting it to most cruisers and some destroyers by 1942. Nelson and Rodney used their 16" guns in AA barrage fire during Operation Pedestal.

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by Bgile » Mon Nov 23, 2009 11:51 am

Isn't it true that at least some of the 8" AA cruisers (LOL) had their gun elevation reduced when they had major overhauls?

I don't see why the Japanese would be surprised since they had AA shells for the Yamato's main battery.

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by lwd » Mon Nov 23, 2009 3:25 pm

dunmunro wrote:
lwd wrote:One that hasn't been mentioned is the Japanese 3.9" gun. My impression is that it had a lot of potential. Indeed if coupled with a radar fire control and proximaty rounds it might have been better than the 5"38.
IIRC, it only fired a 28lb round and would have had a fairly small lethal burst radius, compared to the 55lb 5"/38 round.
ON the otherhand it's higher velocity should allow for greater accuarcy so it might not require as large of lethal radius. Barrel wear however might have been a seirious problem given extended use.

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by yellowtail3 » Mon Nov 23, 2009 3:58 pm

lwd wrote:
dunmunro wrote:
lwd wrote:One that hasn't been mentioned is the Japanese 3.9" gun. My impression is that it had a lot of potential. Indeed if coupled with a radar fire control and proximaty rounds it might have been better than the 5"38.
IIRC, it only fired a 28lb round and would have had a fairly small lethal burst radius, compared to the 55lb 5"/38 round.
ON the otherhand it's higher velocity should allow for greater accuarcy so it might not require as large of lethal radius. Barrel wear however might have been a seirious problem given extended use.
Does more velocity translate to more accuracy? It doesn't in rifles.

I understand the bit about higher velocity giving a larger 'danger area' in surface-to-surface actions, esp. with imprecise ranging finders/equipment - but otherwise, I've not correlated velocity with accuracy. What's the relationship?
Shift Colors... underway.

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by lwd » Mon Nov 23, 2009 4:57 pm

yellowtail3 wrote:
lwd wrote:On the otherhand it's higher velocity should allow for greater accuarcy so it might not require as large of lethal radius. Barrel wear however might have been a seirious problem given extended use.
Does more velocity translate to more accuracy? It doesn't in rifles.

I understand the bit about higher velocity giving a larger 'danger area' in surface-to-surface actions, esp. with imprecise ranging finders/equipment - but otherwise, I've not correlated velocity with accuracy. What's the relationship?
In the AA role the airplanes actually cover a significant distance in the time the shell takes to get there. Shorter time of flight means calculations of how fast the plane is moving and where he is likely to be aren't as critical. Increased P(H) is probably a better term than accuracy.

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by Brett » Sat May 29, 2010 1:28 pm

Though far from ideal as a AA weapon the 6" gun was standard across many countries for light and not so light cruisers. How did it fair in battle on those ships against aircraft? Yes the German ones were SP so more interested the DP versions.

Also what is the heaviest shell that was suitable. I.e 5 L38 are considered excellent but 5 L55 not and the 5.25 get slammed as been too heavy. The Germans had two choices in the 5", naval and AA gun and their specification indicates heavy shells but rates of fire appear respectable so what would be the best compromise between surface and air targets

Cheers Brett

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Re: What was the most effective naval anti-aircraft gun of WW2?

Post by Bgile » Sat May 29, 2010 5:48 pm

Brett wrote:Though far from ideal as a AA weapon the 6" gun was standard across many countries for light and not so light cruisers. How did it fair in battle on those ships against aircraft? Yes the German ones were SP so more interested the DP versions.

Also what is the heaviest shell that was suitable. I.e 5 L38 are considered excellent but 5 L55 not and the 5.25 get slammed as been too heavy. The Germans had two choices in the 5", naval and AA gun and their specification indicates heavy shells but rates of fire appear respectable so what would be the best compromise between surface and air targets

Cheers Brett
The weight of the shell is one major determining factor in rate of fire. It is combined with the ability to maintain a consistent dead time, or the time between removing the shell from the fuse setter and firing the gun. There were complaints about 85 lb shells and not so many about 55 lb shells. Somewhere in there is a reasonable maximum size for the average shell man in navies of the time.

Here is a comment from navweaps.com concerning the 5"/54 (12.7 cm) Mark 16, which was used on the Midway class CVs:

"This gun was not as popular as the 5"/38 (12.7 cm) Mark 12, possibly because the larger projectile and cartridge cases resulted in faster crew fatigue. Essentially, this weapon was simply a longer version of the 5"/38 (12.7 cm) Mark 12 and should not be confused with the later 5"/54 (12.7 cm) weapons which included automatic ammunition feeding provisions."

The shell referred to above weighed about 70 lbs. The shell fired by the British 5.25"/50 used on KGV weighed about 80 lbs. The shell fired by the 5"/38 weighed about 55 lbs.

The rate of fire on the navweaps site:

5"/38 is 15 - 22 rds/min.
5.25"/50 is 7 - 8 rds/min.

I expect the lower number represents extended fire as in a surface engagement, and the upper number represents the rate maintained for a few minutes as in an air attack. Of course it would vary with crew proficiency and the physical attributes of the shell man. Most ships under frequent air attack would have highly proficient crews.

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