# AAA, from 45mm to 57mm: a missed opportunity or waste of resources?



## tomo pauk (May 6, 2012)

The anti-aircraft artillery in calibers ranging from 45mm to 57mm was a rare thing during the ww2. Soviets were using the 45mm AAA in penny packets (mostly/exclusively on their ships), Germans have experimented with 5cm, British with 57mm. 
MY questions being whether such weapons would've provided the combatants with better AA means, or those should be regarded as 'neither fish nor fowl', too heavy to replace the 37-40mm guns, and too weak to replace the heavier stuff?


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## Shortround6 (May 6, 2012)

Most countries realized there was a "hole in the sky" above the height that 37mm-40mm guns were effective and below the height as which 75mm guns and up were effective. The problem came in building a gun to fill the hole. Actually the problem was more in the fuses for the shell and the shells. the 45-60mm shells were too small to have the blast/fragment radius of the 75mm shells, the 47mm bore size being popularly known as the 3pdr and the 57mm the 6pdr vs the 75mm being a 12-17lb projectile. A direct hit was almost necessary. But this called for a much higher rate of fire than the 75mm guns, a rate of fire close to that of the 37-40mm guns, except that the ammo is 2-4 times heavier than the 37-40mm guns. 

They could have replaced neither class of guns but could have denied the use of the band of airspace that the light and heavy guns could not effectively cover. The problem was cost, both in money and in engineering time.


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## Juha (May 6, 2012)

Shortround6 said:


> Most countries realized there was a "hole in the sky" above the height that 37mm-40mm guns were effective and below the height as which 75mm guns and up were effective. The problem came in building a gun to fill the hole. Actually the problem was more in the fuses for the shell and the shells. the 45-60mm shells were too small to have the blast/fragment radius of the 75mm shells, the 47mm bore size being popularly known as the 3pdr and the 57mm the 6pdr vs the 75mm being a 12-17lb projectile. A direct hit was almost necessary. But this called for a much higher rate of fire than the 75mm guns, a rate of fire close to that of the 37-40mm guns, except that the ammo is 2-4 times heavier than the 37-40mm guns.
> 
> They could have replaced neither class of guns but could have denied the use of the band of airspace that the light and heavy guns could not effectively cover. The problem was cost, both in money and in engineering time.


 
I agree with Shortround6
one minor point, 57mm gun would have some A/T potential even against heavier 44-45 tanks as 37-40mm had against tanks in 39-44. See attachment, hits 4 and 10, the latter was penetrating one, are by SU-57-2 AA tank

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## davebender (May 6, 2012)

High velocity 20mm with a high rate of fire works just fine for the army. It's exactly what you need when an enemy fighter-bomber makes a high speed pass at an altitude of 10 meters. It's also very effective against enemy infantry and most other ground targets except main battle tanks. 20mm size weapons are easy to transport and easy to dig into a defensive position. 20mm ammunition is light enough that it doesn't add a large logistical burden to ground troops.

If 57mm has any use at all it would be to defend fixed installations. 37mm flak is effective to 4,800 meters (per Wikipedia) and can fire 250 rounds per minute (Flak 43). The post-war Soviet 57mm AZP S-60 has an effective range of 6,000 meters (per Wikipedia) but rate of fire drops to 120 rounds per minute. I'm not convinced that's a worthwhile trade off. But then I'm not an AA gunner. What does our expert think?


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## tomo pauk (May 7, 2012)

Until we hear from the expert: I've seen the ZSU-57-2 (2 barreled SP AAA, 57mm cannon) firing at same targets as we did in our Pragas (2 x 30mm), achieving decent results vs. those, rather predictable targets(steady curse, not too low, steady speed) They were longer ranged, 4000m vs. 6000m. Since it takes plenty of time to reach 6000m (almost 12 seconds), the radar in the loop seem like mandatory item, if one wants to really capitalize upon that extra range height. 
With 120 rpm, the S-60 ('half' of the ZSU-57-2 armament) was as 'speedy' as the Bofors 40mm L60 of the ww2 fame.

As for the 20mm being just what an Army needs in ww2, seem like no major combatant agreed with that. As for thwarting the attacks made at high speed pass at 10m, nothing short of the radar-cued automatic cannon (or some really good SAM) will cut it, luck being another requirement.


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## davebender (May 7, 2012)

> As for the 20mm being just what an Army needs in ww2, seem like no major combatant agreed with that.


Perhaps not but the German army isn't just any army. Heer divisions were the most capable in the world during both world wars. We've got first hand testimony from experts like Otto Carius stating flakvierling worked exceptionally well against ground targets. I'm not going to question their professional judgement.


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## tomo pauk (May 7, 2012)

If the 20mm was a good thing to employ vs. ground targets, that does not say anything about it's value at it's primary mission, that being killing aircraft - that very German army was puchasing the 37 mm Flak in different 'flavors', while trying to develop, produce and use the 30 and 50mm Flak. Seems like they wanted a bigger stick.


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## Juha (May 7, 2012)

SU-57-2, 2x120rpm


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## Juha (May 7, 2012)

Soviet 57mm AA gun


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## Juha (May 7, 2012)

Most WWII armies fighting in Europe seems to have that 20mm 37/40mm mix, USA had .5 37/40mm mix, Soviet had mg/hmg 37mm mix for automatic AA. 

Juha


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## davebender (May 7, 2012)

You've got it backward. Killing ground targets is the primary purpose of Heer 20mm weapons from WWI (i.e. 20mm Becker) right up to the present day. The large HE payload of German 20mm shells allows these weapons to function in a manner similiar to the Soviet AGS-17 30mm automatic grenade launcher. Protection against CAS aircraft is just a bonus.

37mm flak was primarily intended for air defense.


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## Juha (May 8, 2012)

davebender said:


> You've got it backward. Killing ground targets is the primary purpose of Heer 20mm weapons from WWI (i.e. 20mm Becker) right up to the present day. The large HE payload of German 20mm shells allows these weapons to function in a manner similiar to the Soviet AGS-17 30mm automatic grenade launcher. Protection against CAS aircraft is just a bonus.
> 
> 37mm flak was primarily intended for air defense.



Really, why then 20mm AA guns were given to Army AA units? And even in 1941 PzDivs usually had only 20mm Flak, they got 37mm later on. The other 20mm were 2cm KwK 30 38, the main armament of Pz II

Juha


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## Shortround6 (May 8, 2012)

davebender said:


> You've got it backward. Killing ground targets is the primary purpose of Heer 20mm weapons from WWI (i.e. 20mm Becker) right up to the present day. The large HE payload of German 20mm shells allows these weapons to function in a manner similiar to the Soviet AGS-17 30mm automatic grenade launcher. Protection against CAS aircraft is just a bonus.
> 
> 37mm flak was primarily intended for air defense.



What a load of horse manure. 

1. the 20 X 138 cartridge used by the Flak guns didn't use the high HE capacity ammo until well into WW II so the HE capacity could _NOT_ have been intended for use against ground targets in the early 30s when the ammo the first guns for it were adopted. 
2. With the German shells you have either/or situation. Either you have a 120-130gm shell with about 10gm explosive or you have a much lighter shell with a thinner body and twice the explosive but fewer shell splinters/fragments. Small explosions without much for fragments do crap in the open air. Russian 30mm grenades weigh 275gm, have up to 40gm explosive _AND_ a pre notched internal fragmentation sleeve for a lethal radius of 6-7meters.
3. The Russian grenade launcher weighs about 30kg with tripod and without ammo. It is man portable. a single 20mm German AA gun is not. A Flak 30 weighs about 450kg in firing position and about 740kg ready to travel. also without ammo. German 75mm infantry gun only weighs 400kg. Compared to 8cm mortars the 20mm gun in ground mode is a joke for HE delivery.

The German 20mm guns were used against ground targets but it was not their primary purpose either when planned or adopted. The American .50cal was effective against infantry too but that was not the reason it was adopted either. The .50cal was adopted as both an AA weapon AND as an anti-tank weapon. Last time I checked tanks were ground targets so one _could_ say that the .50 was adopted for use against ground targets but it certainly wasn't adopted as an anti-infantry weapon. This was pre WW II when anti-tank rifles were very popular (and effective against the light tanks of the time) so having a full automatic gun that fired an "anti-tank" cartridge was seen as a good thing. 

The German 20mm guns were intended for air defense, usefulness against ground targets was secondary. Using your 20mm AA guns to shoot your infantry onto a target or to repel and an attack is fine if it works, Loosing your AA assets to Vickers guns (or Maxim guns) or 3in-82mm mortars and then being hit by aircraft may not seem so smart. The aircraft could show up days (or weeks) later.


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## davebender (May 8, 2012)

Originally developed for use in anti-tank rifles and later adopted for use in German light flak. Hence effectiveness against ground targets was known from the beginning.


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## Shortround6 (May 8, 2012)

davebender said:


> Originally developed for use in anti-tank rifles and later adopted for use in German light flak. Hence effectiveness against ground targets was known from the beginning.



Really? and your proof of this is?

20 X 138 cartridge may have first been used in Swiss ST-5 AA gun which was later developed into the Flak 30. The early Swiss built anti-tank rifles started with a fairly low powered 20mm round, moved to the 20 X 105 case (the S-18/100) and finally to the 20 X 138 round with the S-18/1000 model. 
British were testing a S-18/100 in 1934, which makes the idea that the Flak 30 used a cartridge developed for a later model than 1934 AT rifle a little doubtful.


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## tomo pauk (May 8, 2012)

davebender said:


> You've got it backward. Killing ground targets is the primary purpose of Heer 20mm weapons from WWI (i.e. 20mm Becker) right up to the present day. The large HE payload of German 20mm shells allows these weapons to function in a manner similiar to the Soviet AGS-17 30mm automatic grenade launcher. Protection against CAS aircraft is just a bonus.
> 
> 37mm flak was primarily intended for air defense.



Since the name was 'Flak', not 'Iak', I'd say the purpose of the German 2cm Flak weaponry was indeed to fight 'flugzeug', not 'infanterie'  The Luftwaffe was one of the major users, so that further points towards the intended use - killing aircraft. SR6 covered the HE vs. total shell weight ratio.


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## davebender (May 8, 2012)

Luftwaffe 2cm, 3.7cm, 5cm and 8.8cm weapons were intended for use against aircraft. The Heer had different priorities.


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## Juha (May 8, 2012)

davebender said:


> Luftwaffe 2cm, 3.7cm, 5cm and 8.8cm weapons were intended for use against aircraft. The Heer had different priorities.



If so, why Heer gave the 2cm FlaK to its AA units? And where you got the idea that Heeres Fla units were not for AA but for ground support?

Juha


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## Shortround6 (May 9, 2012)

davebender said:


> Luftwaffe 2cm, 3.7cm, 5cm and 8.8cm weapons were intended for use against aircraft. The Heer had different priorities.



How many 2cm, 3.7cm, 5cm and 8.8cm *AA* weapons did the Heer even have? Many of the "Heer's" anti-aircraft weapons were actually in Luftwaffe units attached to Heer formations as in an a Luftwaffe AA battalion being attached to a Heer infantry division. 

The Heer had a lot of 2cm, 3.7cm, 5cm weapons but they weren't the same guns as the AA guns let alone the same mounts.


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## foxhound (May 28, 2015)

Juha said:


> I agree with Shortround6
> one minor point, 57mm gun would have some A/T potential even against heavier 44-45 tanks as 37-40mm had against tanks in 39-44. See attachment, hits 4 and 10, the latter was penetrating one, are by SU-57-2 AA tank


Thx very much for this very usefull photo, and information. It would be interresting to know from what distance the AZP S-60 could achieve this performance ? 500 M ? 1500 M ? If it is above 5.000 M with its HE-T, or HEAT-if it could for the last models ?- it could be a terrible deterrence against figther-bombers, including F-15 E, A-10 and F-22.
Can you give us more details please ?

Thx


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## CharlesBronson (May 30, 2015)

I think for ww2 this range of calibers were too damn heavy for a dependable automatic weapon, in the 1950s the technology was advancing fast enough to obtain fully reliable automatic weapons in 57, 75 and 76mm. The pot war Soviet 57mm is particulary good example of a good design, cant tell if they were ever equipped with proxymity fuzes, probably not.


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## Jabberwocky (Jun 16, 2015)

The Germans tried several 50 mm and 55 mm AAA designs, with a notable lack of success. 

The nominal effective ceiling of 37 mm weapons was about 4-4500 m, but in reality it was closer to 2500 m with visual aiming. This created a AAA 'deadzone' - in reality, just a less than optimal zone for the light AA/heavy AA crossover, between 3000 and 4500 m where Allied medium bombers could operate.

Theoretically, a 50 mm class weapon was the solution to this, with a proper effective range of about 3500-4200 m, but the designs never quite worked right. The 5 cm Flak 41 was slow firing and heavy, and the ammunition was ill-suited to its requirements, with a smallish amount of HE filler and a tendency to tumble at high velocity. 

The 55 mm Gerat 58 derivative was started with this in mind. They upped the M/V to 1050 m/sec and increased the HE capacity of the round by about 20%. The rate of fire suffered with the bigger weapon. With the five round clips used (which weighed over 30 kg each), the gun fired at about 60-70 rpm. This wasn't too bad though, as the single barrel 37 mm/40 mm class weapons really only had practical RoFs ranging from 60 to 120 rpm.

The Gerat 58 wasn't fully finished by the time the war ended. The actual design itself was reasonably solid though. It formed the basis for the post-war Soviet S-60 57 mm gun, which was a very successful design. 

The 5.5 cm flak was reckoned to have an effective range of about 4000 m with visual aiming, about 5200 m when radar controlled. The weapon was very powerful, with a M/V of just over 1000 m/sec (compared to around 800 m/sec for the 37 mm flak and 880 m/sec for the Bofors).


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## RCAFson (Jul 18, 2015)

tomo pauk said:


> The anti-aircraft artillery in calibers ranging from 45mm to 57mm was a rare thing during the ww2. Soviets were using the 45mm AAA in penny packets (mostly/exclusively on their ships), Germans have experimented with 5cm, British with 57mm.
> MY questions being whether such weapons would've provided the combatants with better AA means, or those should be regarded as 'neither fish nor fowl', too heavy to replace the 37-40mm guns, and too weak to replace the heavier stuff?



WW2 AA can be divided into autocannon firing contact fuzed ammo and manually loaded cannon firing MT or VT ammo. ~75mm is the smallest shell size that can accomodate MT/VT fuzes. Below ~75mm shells typically used contact fuzes, and since these shells must strike the target, hit probability is low unless a very high volume of fire can be developed. Against a typical WW2 aircraft, a 40mm shell probably provided a high enough kill probability per hit that it would be more lethal than larger but slower firing autocannon.


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## Shortround6 (Jul 18, 2015)

That is pretty much the story. The 3in/75mm Proximity fuse becoming possible later in the war than the 4-5in/100-127mm proximity fuse. Now throw in that the 'rule of thumb' for gun size/weight was proportional to the cube of the caliber and a 50mm gun would be roughly twice the size/weight of a 40mm (and so would the ammo) and trying to make high cycle rate 50-60mm guns becomes rather difficult. They tend to get rather large and heavy pretty quick.


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## cherry blossom (Jul 20, 2015)

Although all the discussion in this thread up to now has been on land based AA guns, there may have been a specific need during WW2 for a 45 mm to 57 mm automatic AA gun to protect battleships from torpedo bombers as I tried to mention in a previous thread http://www.ww2aircraft.net/forum/ww...40-mm-choose-36310-post994276.html#post994276. By 1944-5, torpedoes could be dropped from a fair height and at reasonable speed. 800 ft and 260 knots were recommended by the USN, causing the torpedo to fly about 1,000 yards after being released before entering the water. Thus the release point would be about 1,400 yards from the target ship. The torpedo bomber needed to fly for perhaps 20 seconds without banking to set the gyros. The bomber could evade by diving (I am not sure if the pilot could kick the rudder bar) but had to fly a fairly predictable path from about 3,500 yards out to the dropping point. Thus there was a need to get shells out to 3,500 yards quickly and Musashi in October 1944 could have benefited from replacing some of its 25 mm weapons with something like the German 55 mm Gërat 58. 
I specified battleships because the constraint of space was more significant than weight for battleships. The Yamato Class had 40 triple 25 mm mounts with each weighing 1.8 tons (all weights from NavWeaps - Naval Weapons, Naval Technology and Naval Reunions - Navy Weapons) which could have been replaced by weapons with a much longer effective range. For example, the last battleship to be completed ( some time after the end of WW2) was Jean Bart, which was equipped with twin 57 mm Bofors in 16 ton turrets. Its near contemporary Vanguard had sextuple 40 mm Bofors in 21 ton mountings showing an alternative approach to the same problem.


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## Shortround6 (Jul 20, 2015)

The American Navy jumped the 50-57mm size and went for the 3in. However it took until several years post war for it to come into service. 

The Japanese had a real problem because the 25mm was in no way, shape or form equal to 37-40mm guns and the Japanese fire control for even the triple mounts was rudimentary compared to later fire control for 40mm Bofors guns. Only a few triples had RPC. Please note that at the longer ranges good fire control is essential. American 40mm ammo took 8.5 seconds to reach 4200 yds. A 235mph airplane will cover about 1000yds in that amount of time. Time of flight for a 50-57mm round will be a bit shorter but the effective limit on range is more a function of fire control than Ballistics. 

WHile much heavier than a Japanese 25mm the 40mm Bofors fired at about the same speed, used a shell about 3 1/2 times heavier and had a shorter time of flight to the "longer" ranges. 

The German 55mm fired at about the same speed (most of the guns varied a bit and often fired at different rates of fire depending on elevation, I don't get too excited about the difference between 120rpm and 140rpm. It fired a much heavier projectile about 20% faster at the muzzle but this only cut the time of flight to 4370 yds ( a bit further) to 6.75 seconds. Our 235mph plane can cover about 775yds (about 59 plane lengths for a 39ft long plane) in that amount of time. So greater "effective range" without radar ranging and a good predictor/director is pretty much an illusion.


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