# Light AAA: 20, 25, 30, 37, 40 mm - what to choose?



## tomo pauk (Mar 9, 2013)

What kind of light anti-aircraft artillery was the best answer for the needs of the ground- and/or ship-based air defense? Maybe choosing curious Swiss guns in 24 or 34 mm caliber? Can one caliber fit the roles for all? 

The secondary capabilities, like armor-piercing performance, is not important here.


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## Shortround6 (Mar 9, 2013)

One caliber does not fit all.

as a _very_ rough rule of thumb, shell weight goes up with the cube of the diameter. 40mm shell is 8 times heavier than a 20mm shell. Gun weight also goes up in proportion, A 40mm is not going to be twice as heavy as a 20mm or even 4 times as heavy but closer to eight times heavier.


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## vinnye (Mar 9, 2013)

I would guess that a lot of what you want from your AAA depends upon the threat?
Conventional air attack or Kamikaze?
The perceived wisdom is a little heavier calibre shell to "kill" a Kamikaze rather than just damage the aircraft.


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## dobbie (Mar 9, 2013)

Good question. I served in air defense artillery back in the 1970s on the Vulcan M163/M167 series. It was a 20MM 6 barreled gatling gun firing 3000 RPM with a range only radar. Pretty good setup really. Mounted on an electric turret and the M163 was fitted to a modified M113. Didnt care much for the radar system, and when I qualified shut it off and caged the sight. When youre tossing out that much lead, to me its like duck hunting...just lead the target and youll get there. We were paired up with the Chapparal missile system which was the Army's version of the AIM9C Sidewinder, which is a tail chase only system. Its my understanding that they ran the Vulcan through some product improvement programs to upgrade the radar and such, but the Vulcan was retired because some of the Soviet attack aircraft were armored against the 20MM. 
We had 2 muzzle clamps for the vulcan. The so called ground clamp would put the firepower in more or less a straight line, and the air defense clamp forced the barrels into an elliptical shape which threw a pattern out to 3000 meters. Never saw much use for it but I might be the exception to the rule. On my last qualification, we shot at what is known as BATS, or ballistic aerial target system....it was a spin stabilized aluminum rocket about 15 feet long, launched with 3 2.75 rocket motors. I heard the speed was about 300 mph but I dont know it for a fact. I did cut one of those rockets in two with a 60 round burst.
And it certainly depends upon what sort of aerial attack youre facing. If its of the Kamikazee attack type, youre going to want to reach out pretty far in order to make them break up in the air or fall short of your position. The Navy used the 5 inch 38s with a proximity fuze to defend their ships. The 40MM and smaller could knock the aircraft down but not before it crashed into the ship.


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## tomo pauk (Mar 10, 2013)

Another AA gunner  Welcome at the forum.

I've served along 30mm, mounted on Praga V3S armoured truck (all Czech made) back in Yugoslavia, 1990-91. No radar there, just optics with 'spider web'. Our regiment's missile part were truck-borne Strela 2 (SA-7) teams. Four 30mm bateries (self propelled), two 20mm batteries (towed, three barreled) and one Strela battery was the regiment, plus radar and logistics.


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## Ascent (Mar 10, 2013)

With light AAA chances are you're target is flying low so a high rate of fire is required maximise the fleeting opportunitys that you get combined with the maximum punch available for the hits you do get. I think for WWII guns 20mm is probably your best bet for a ground mount but you may want something heavier on a ship where you may be able to aquire your target at a longer range, maybe around the 40mm range.


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## Denniss (Mar 10, 2013)

Rapid-firing 2cm for short-range defense and the 40mm Bofors guns for longer-range defense (or against heavier armored a/c like the Il-2)


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## davebender (Mar 10, 2013)

If use against ground targets doesn't matter then weapons 37mm to 40mm in size are all you need for light AA protection during WWII. 

WWII era 20mm is useless for anything except shooting at strafing fighter aircraft. Most of the time bombs would be dropped outside 20mm range. 

One could make an argument for high velocity weapons 25mm to 35mm in size such as Japanese 25mm/60, USN 1.1"/75 (28mm), German 3cm Mk103 and 30mm M53 (Under development during WWII. Completed post war.).


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## tomo pauk (Mar 10, 2013)

The 28 or 30mm round might be a good place to start, if one would want to have both high RoF, good punch and not too much of weight?


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## cherry blossom (Mar 10, 2013)

There are some distinctions even if we stick to defending ships. If you do not have power, you almost have to use a 20 mm weapon. The Japanese compained that only the strongest men could use the manually swung 25 mm although the IJN had chosen it after comparing it with the Oerlikon 20 mm. 

However, a 20 mm can only hit an aircraft after it has already dropped its bombs or torpedoes and it can only shoot at an aircraft that has attacked its own ship. It cannot do much to help the rest of the fleet.

If you have power available, you can use weapons that reach out further. One issue is that you need to reach out much further as WW2 proceeds. It is much easier to defend a ship against early WW2 American or German torpedoes than against late war American 
_View: https://www.youtube.com/watch?v=R552QfbD8AU_. Kamikaze aircraft are also best kept at a good distance. 

Probably the best “light” weapons would have been the German 55 mm, the Bofor 57 mm or the Russian and Czech 57 mm introduced post war. However, the best weapons actually used in WW2 were probably the German 37 mm M43 and the even better 40 mm Bofor. The Americans went for 3 inch or 75 mm guns with proximity fuses postwar.

After watching the Youtube video, these times of flight for WW2 AA weapons may be of interest.

Germany 5.5 cm/77 (2.17") Gerät 58

Time of flight with MV = 3,350 fps (1,020 mps)
1,090 yards (1,000 m): 1.10 seconds
2,190 yards (2,000 m): 2.50 seconds
3,280 yards (3,000 m): 4.34 seconds
4,370 yards (4,000 m): 6.75 seconds


Sweden, Britain, USA, Germany and Japan Bofors 40 mm/56 (1.57") Model 1936

Time of flight for 1.985 lbs. (0.900 kg) HE shell with MV = 2,890 fps (881 mps)
4,200 yards (3,840 m): 8.5 seconds
4,500 yards (4,110 m): 10.5 seconds

USA 5"/38 (12.7 cm) Mark 12

Time of flight for AAC projectile with MV = 2,500 fps (762 mps):
5,000 yards (4,570 m): 8.0 seconds
10,000 yards (9,140 m): 22.0 seconds
15,000 yards (13,720 m): 43.0 seconds
17,270 yards (15,790 m): 68.8 seconds


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## davebender (Mar 11, 2013)

> 30mm round might be a good place to start, if one would want to have both high RoF, good punch and not too much of weight?


That's where Germany was heading with the LM44U twin mount developed during 1943. Hydraulic training and elevation controlled by a joy stick.

I believe 30mm M53 cannon was intended for naval version on Type XXI submarines and other such small vessels. Heer version (i.e. Kugelblitz) was to have a pair of 3cm Mk103 cannon. Either way it was a formidable and rather modern weapons system.

Apparently Germany lost patent rights to their almost ready M53 cannon. Otherwise an updated version of that weapon might have armed the Gepard flakpanzer ILO 35mm Oerlikon cannon.


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## tomo pauk (Mar 11, 2013)

The M53 was actually the development of the MK-303 ("_Brunn cannone_", ie. Brno (Czech city famous for it's weapon industry) cannon), the Mk 303 was being designed under German authority. For the Kugelblitz, the Germans used two known MK 103 cannons.
The Gepard is an awesome system, the 35mm being far more powerful than any 30mm.

This baby would be devastating, the quadruple MK 103 on Wirbelwind basis:

http://forum.valka.cz/files/zerstorer_213.jpg


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## davebender (Mar 11, 2013)

30mm is smaller and lighter. Gepard could have been a smaller and less expensive weapons system. Alternately they might have built a German version of Soviet ZSU-23-4 armed with four M53 30mm cannon.


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## tomo pauk (Mar 11, 2013)

The high cost of the Gepard was much due to it's radar-assisted FCS (featuring both warning and aiming radar), and the chassis based upon a tank. If we want to replace the pair of 35mm with 2 pairs of 30mm, the savings would not be worth it (if any would be achieved). 
If we imagine Germans going with pair of 30mm on a tracked AFV (Marder-based?), still with fully-fledged radar FCS, we have too much of radar for too little of a punch? If the radar system installed is aiming-only, the resulting system is also far less capable than Gepard, especially if one wants to tackle ATGM-armed Hinds at appropriate ranges.


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## Shortround6 (Mar 11, 2013)

Russian ZSU-23 gun weighs 165lbs and is belt feed. 

Hispano HS 830 30mm gun weighs 299lbs and is belt feed. 

I believe Tomo has the information for the M-53 because I think the information in Tony Williams book is off a bit. 

The Oerlikon 35mm is in a whole different class as Tomo says. Weight depends on the model but goes from 430kg to 670 kg ( 946lb to 1474lbs) peak recoil for most models is about twice the Hispano 30mm. It fires a 550gm shell about 100ms faster than the Hispano fires a 360gram shell.

The M53 fires a 450gm shell about 80ms slower than the Hispano?


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## tomo pauk (Mar 11, 2013)

The M-53 fires a shell weighting 430g at 1000 m/s (whole round was a tad above 1 kg), the cannon weights 272kg. Magazine-fed, RoF was '7 shells a second per barrel', Tony Williams saying 450-500 rpg. The M-53 was strip-feed, 10 rounds per strip

Now this is unbelievable, 'my own' Praga (was the commander on it), the 10998 (the 1st picture):

Samohodni PA top Praga M-53/59

The photo was taken at the Jezersko border crossing (Slovenia - Austria), during the brief Slovenian was in 1991. You can note the board that was to help out foreign drivers tourists entering the former Yugoslavia there. The building to the left was where the customs were located, the Slovenians surrendered after several hits from Praga in the roof of the building. Our food supplies were not sufficient to hold them as prisoners, so our command decided to let them go after couple of hours.
Once we captured the border crossing from Slovenian territorial defense, the Slovenians have blocked the road leading to the border crossing. We were to leave the border crossing to the 'federal' police, after a day or two, but that never happened. So after the 3rd day, our command agreed to retreat to the Army border station, minus the Pragas, so we've stripped the sights, accumulators, ammo, breaches, even the jerry cans from our Pragas, stuffed that into our truck and retreated. The photo depicts the Praga stripped off from necessary stuff. After several days we returned to Kranj, where my father visited me, the 1st time I saw him crying. 
The Pragas were returned after 10 days (the war ended prior that), I've left the Army shortly after that along with 7 other Croats.


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## dobbie (Mar 12, 2013)

If the us army wanted to go back to air defense artillery for low level coverage, I think the GAU-8, currently used in the A10 Warthog should be a prime candidate. Put it on a light tracked chassis for mobility and unlike a missile system alone, you have a pretty good anti infantry weapon. Fires 4200 rpm and the ballistics are better than the old M61 20MM ammunition. Combine it with the current Patriot system, and Id say you have good coverage high and low.

The M163 was field tested in Viet Nam for 6 months, mostly road convoy defense and did a pretty good job. They took the radar set off and mounted a belt fed 7.52 in its place. 

If you have to destroy the aircraft, as was necessary for the Kamikazee attacks, its going to take a larger caliber and because of that, a slower cycling cannon. At low level, more rpm is better. As to the aircraft already dropping their bombs before theyre engaged, typical AA batteries are set up in a web which gives them the opportunity to engage the enemy aircraft before they can reach the target with overlapping fields of fire. The individual sites use different radar frequencies so as not to interfere with neighboring sites, and if firing over friendly troops, a self destruct warhead is used to prevent the shells from killing friendlies. On the Vulcan, we used High Explosive Incindiary Self Destruct warheads.


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## davebender (Mar 12, 2013)

I have a dumb question.

Historically Croatia - Slavonia was a single province within the Hapsburg Empire. Why didn't they become a single nation when Yugoslavia broke up?


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## tomo pauk (Mar 12, 2013)

Do you mean 'why Croatia-Slavonia did not became a separate nation'? Croats have had a majority (50% or more) in the area of Croatia-Slavonia from the map (minus the area around Novi Sad), Dalmatia and Istria. In Bosnia and Herzegovina Croats presented maybe 30% of population, the B-H being sorta leopard skin as far as nation map is concerned. Once the A-H ceased to exist, Istria, along with some islands and city of Zadar/Zara become part of Italy (war spoils). The Kingdom of Serbs, Croats and Slovenes was announced shortly, under Serb dynasty of Karadjordjevich. The transition was not a smooth one, many Croats believing that we have get rid of one apsolutist, only to be saddled by another. Not much to do really against the sudden union, Serbs were the part of a side that won ww1, Croats and Slovenes were not. 
In the new state, the Macedonians, Montenegrins and Muslims were not legally able to declare them as members of such nationality, the Montenegro being also absorbed in the new state.


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## Denniss (Mar 13, 2013)

dobbie said:


> If the us army wanted to go back to air defense artillery for low level coverage, I think the GAU-8, currently used in the A10 Warthog should be a prime candidate. Put it on a light tracked chassis for mobility and unlike a missile system alone, you have a pretty good anti infantry weapon. Fires 4200 rpm and the ballistics are better than the old M61 20MM ammunition. Combine it with the current Patriot system, and Id say you have good coverage high and low.


That must be a rather large tracked chassis to install the GAU-8 onto but that won't be possible with a rotating turret.
image: http://commons.wikimedia.org/wiki/File:GAU-8_meets_VW_Type_1.jpg


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## dobbie (Mar 13, 2013)

Of course its possible to put a GAU 8 on a tracked chassis and a rotating turrel. For one thing, the feed system doesnt have to be mounted behind the weapon as it is with the A10. That was done in order to fit it in an aircraft fuselage. On the M163, we had a 2100 rd linkless drum feed which was at the base of the turret, underneath the gunners seat. Probably would want a similar set up for what I propose because of the weight of the drum and ammo, keeping most of the weight as close to the pivot point as possible. Some of the weight and complexity is going to go away because you would not need to cycle fired cases back into the drum-those can be tossed over the side. So far as the weight of the chassis is concerned, you wouldnt need a heavily armored chassis, just one large enough to contain the turret, crew and the feed mechanism. We used a modified M113 and the rear ramp was quite handy for rolling out the belts.


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## tomo pauk (Mar 13, 2013)

The US were testing the T250 Vigilante, a 37mm Gatling gun mounted at the lengthened M113 chassis. The gun was later modified to fire 35mm ammo, the same as used at Gepard.

THE RED QUEEN AND THE VIGILANTE


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## dobbie (Mar 13, 2013)

tomo pauk said:


> The US were testing the T250 Vigilante, a 37mm Gatling gun mounted at the lengthened M113 chassis. The gun was later modified to fire 35mm ammo, the same as used at Gepard.
> 
> THE RED QUEEN AND THE VIGILANTE



Interesting weapon, Tomo Pauk. Odd looking magazine feed but I understand the concept.


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## tomo pauk (Mar 13, 2013)

Indeed - the weapon itself would not be out of it's place in this century either. It was capable for 3000 rpm almost half a century before Oerlikon was boasting with 1000 rpm with their 35/1000, or 'Millenium' gun.


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## tomo pauk (Mar 13, 2013)

The thread is creeping towards Cold war, where the Soviets have had the world beater among SP AAA, late 1950s: the twin 37mm, radar directed 'Yenisei' system. Though it passed tests, Soviets opted for Shilka, quadruple 23mm. Hence robbing themselves and their allies from maybe another 2 km of slant range and 1 km of altitude. Picture:

http://militaryrussia.ru/i/284/401/dEvmJ.jpg

More about it, multi-page article, can be translated:

http://ser-sarajkin.narod2.ru/ALL_OUT/TiVOut10/ZSU372En/ZSU372En011.htm


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## dobbie (Mar 14, 2013)

If we are limited to what was available in WWII, Id say the Bofors 40MM is a good candidate for a light AA weapon. Reliable and easy to maintain, fairly accurate. The US Army saw fit to put a couple of them in an open turret on a light tank chassis and called it the Duster. M42 Duster - Wikipedia, the free encyclopedia
Although the chassis is post WWII, I see no reason why it couldnt have been adapted to the M4 Sherman.


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## tomo pauk (Mar 14, 2013)

The Flak 43 (37mm) might have been the best of ww2, with good RoF, firing a sizable shell on decent muzzle velocity. The twinned such Flak should be a devastating thing.


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## RCAFson (Mar 14, 2013)

Octuple pom-pom = 920rpm x 1.8lbs per round, = 1656 lbs per minute. 1120 rounds on mount = 73 seconds firing time but has continuous reload capability.
Max range = ~7000 yds. Remote control via off mount director, (one man control possible) and thus full computer control capable with no crew requirements.

Phalanx Block 0 = 3000rpm x .22lb per round = 660lbs per minute. = 989 rounds on mount = 9.8 seconds firing time with 10 to 30 minutes reload cycle
Max range = 6000 yds. Automatic and remote control.


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## Shortround6 (Mar 15, 2013)

dobbie said:


> Although the chassis is post WWII, I see no reason why it couldnt have been adapted to the M4 Sherman.



Didn't need to, it fit quite nicely on the M-24 chassis as the M-19







Which was developed from several earlier prototypes using stretched M3/M5 chassis with 3 bogies instead of 2. 

In addition to having lots of fighters the US had half-tracks with quad .50s, a 37mm with two .50s and a host of protoypes including one half track with twin 40mm guns, one mounted on top of the other, way too much gun for the chassis.


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