Historical Questions about those dang 20mm guns..

[Franko]

Okay, I just have a couple of questions for you hardcores out there...

1. The 20mm gun featured in the German arsenal in CM -- are those rounds actually "explosive", meaning, did they actually blow up like a grenade? how was it set off? on impact? I confess I don't know much about ballistics and the like, but I'm curious..does anyone have any specs on those? Or are they just big slugs like the .50 cal?

2. I read a historical source somewhere that stated that those 20mm guns were VERY frequent tank killers on the Eastern Front..simply because they drove Russian tank crews MAD because of the enormous banging that would result from multiple hits on a steel tank. Any truth to this? Have any historical sources?

Thanks! You geeks..I love ya.

Frank

[gunnergoz]

Hi

AFAIK the 20mm fuze was impact only and yes the round did explode like a small grenade if you will. Very messy if it hit a human, from what I read the scene of a man blowing up in the film Saving Private Ryan was pretty realistic.

As to the issue of being a tank killer, I could surmise that an inexperienced or panicky crew might take badly to the rounds exploding on their hull. The rounds might also do significant damage to external objects like periscopes, radio antenna, fuel tanks etc and that might KO the tank for that encounter at least. A lucky hit might damage track links or suspension components which were'nt always well protected.

All in all, a very versatile weapon!

[Stalin's Organ]

IIRC the Allies had an APHEI-T round for air-to-air use - that is an armour piercing nose, HE and Incendiary fillings, and a ttracer base. So there's enough room to get complicated in a small round!

Also I read somewhere that most of hte Matilda's actually KO'd at Arras were done so by 20mm fire setting fire to the storage containers on their exterior!

[Paco QNS]

I cite my quote from the thread

Fast recon, how to beat it in ungamey manner

<BLOCKQUOTE>quote:</font><HR>On the dual role of light AA guns, I cite a few excerpts of doctrine.

From the "Normas generales para empleo táctico de las armas de

acompañamiento de infantería y caballería" Instrucción E. 8.

approved 24, June, 1940 (distributed 30, October, 1940) Spanish Army

(very german influenced since the Spanish Civil War)

(General guidelines for the tactical employ of supporting weapons,

Infantry and Cavalry):

""Anti-air machineguns 20 m/m

74. The general missions of these weapons in combat are two:

Main mission, defense against airplanes

and secondary mission, antitank.

75. Their main missions are:

Defense of marching or stationary units.

Idem of materials.

Idem of depots.

Idem of AA batteries.

Idem of field artillery units.

And in general, of everything that, needing AA defense, don´t have any

guns for it.

76. The little charge of shells and the fuzes used (ultra-quick or anti

-armour) makes them poor suited for use against land targets.

Only exceptionally they can be used against nests or observatory points,

exclusively using their excellent precision to hit their slits.

Mission Anti Air

...

Mission Anti Tank

79. Their effective range with armour piercing ammo is 500 metres,

corresponding with the lighting trazes. To this range it can pierce

a 20 m/m armour and, their precision for a 50% hits percentage is

0,5 metres vertical and 0,25 horizontal.

The traze permits to correct fire easy and quickly.

80. Their main targets are light and semi-heavy tanks, whose high

mobility requires to use automatic fire weapons with traze ammo.

81. Their main purpose are:

Attack the aforementioned tanks, when protecting the enemy infantry

advance.

It must be remembered that this antitank mission is secundary, it can´t

overrule their main purpose, and, then, generally, the weapons will

be sited in the better anti air emplacement, and in case from it they

can acomplish the anti tank role, as a secundary mission this latter,

and, of course, always in short and medium ranges.

Employment

...

Defensive

86. In general, they will be employed in the resistance position, so

sited to defend first the main line of resistance, the support line and

the stopping line, and, in case is possible, the Regiment reserves

line. Their emplacements will form a rectangle in the majority of

occasions.

87. In special cases, when the advance position is ordered to resist,

a gun will be assigned to it, siting the other three in the resistance

position, forming an equal triangle to protect effectively the main,

resistance and stopping lines.""

So, to this light, I don´t see as "gamey" the reasonable use of light

AA guns (that is, not more of six for a reinforced infantry battalion,

and siting them in dual role emplacements). In fact, the main

protection of the supply lines will be by daylight camo and moving only

by night. A few AA guns will only "draw fire" to them.

Nonetheless, the idea of buying them and siting them off map to

protect artillery and reinforcements has merit, IMO.<HR></BLOCKQUOTE>

The proyectile weight was 0,119 Kg (for Oerlikon, Polsten and Flak 30/38); 0,125 Kg for the Scotti and 0,135 Kg for Breda and Type 98. The explosive was very small, and you must remember, due to the high Vo, it needed to be mixed -not to explode in the gun-. ((that is in the HE anti air proyectile model; the armour piercing were probably solid shots)).

With untrained crews I think is possible the facts given. After all, a tank is no more than a "mobile box used to retain valor".

Regards.

((I liked very much your scenarios, Franko. -especially ABH. Also your rules Franko´s True Combat))

[YECoyote]

Damn it Gun, you're too fast. I was going to refer to the scene is Saving Private Ryan too.

I found this site a little while ago:

wargamer.org

[Slapdragon]

On the subject of light weapons killing tanks, Isreali air spotters claim to have killed Arab tanks in 1967 with a coke bottle. They claim that Arab tankers feared being hit by th M40 recoiless, so they would bail out if they heard the spotting roung hitting the tank. The spotters would fly low and fling out coke bottles. It the arabs bailed, they would machinegun the crew.

Is it true? Who knows, but it makes a great urban legend.

[JasonC]

The problem with Pacos' otherwise interesting document is its date and place, 1940 and Spain. As such, it reflects (as he says) the experience of fighting against early model, pre-war tanks. 20mm FLAK could penetrate the thin sheet metal protecting light armor, but the major combatants in the real war - even in the west in 1940 - were using tanks with heavier armor, generally proof against 20mm FLAK.

They were certainly used in a ground role. But nothing like 6 per battalion, as one fellow implied. Entire infantry divisions often had only 12 of them (as one company of the divisional AT battalion), and sometimes none at all. They were typically deployed with four as a battery, or two as a section, to defend a key point or a particular unit - such as HQs, artillery batteries, bridges, and sometimes forward infantry positions.

In practice, the Germans used them along with heavy machinegun teams, 81mm mortars, 75mm infantry guns, and 37mm, 50mm, and (only late in the war) 75mm PAK, as "heavy weapons". These heavy weapons provided the direct fire -reach- of infantry strongpoints, enabling them to suppress infantry attackers a long way off and above all to cover the gaps between strongpoints by fire. Only the PAK provided serious AT capability at range, and in the case of the lighter ones (37mm especially) even they often did not provide much. But the rest provided good anti-personnel firepower, and could stop thin skinned trucks and such.

The direct fire of the heavy weapons, supplimented by artillery barrages called from farther back, were supposed to stop infantry and force any motorized units to unload. If some infantry got through the zone of heavy weapons fire, it was supposed to be depleted enough that it could not reduce the strongpoints directly. It could infiltrate between them, but disorganized and reduced. Then counterattack forces would hit the sides of the penetrations and wipe out the intruders.

It was not the number of any one type of heavy weapon - including 20mm FLAK - that could produce this effect, but the cumulative firepower of all of them combined. An infantry battalion might or might not have 2-4 20mm FLAK. But it would have 6-12 81mm mortars (2 per company and battalion level ones, but sometimes only one or the other), 2-4 75mm infantry guns, 2-4 PAK, and a dozen or more heavy machineguns. A supporting artillery battalion would add the fire of a dozen more heavier guns when possible. So overall, soft targets trying to penetrate the strongpoint zone would encounter the fire of 25-50 support weapons, and often the fire of a dozen of them (overall) on any given avenue of advance.

Organizationally, some of these weapons were at the company level (HMGs and 81mm mortars), others at battalion or regiment (the infantry guns, a few PAK), or assigned to a regiment (or KG) from divisional assets (heavy PAK from the divisional AT battalion, light or heavy FLAK likewise or in a seperate divisional FLAK battalion, artillery support from the artillery regiment, etc). Tactically, they were sited in company or battalion level strongpoints along the line, or in a second "tier" of strongpoints ~1 km or less behind the infantry ones and covering gaps between them in checkerboard fashion, to make greater use of their range when terrain allowed it.

Facing only a few heavy PAK, full blown tank units could usually get through such a defensive zone, between the strongpoints. With only a few tanks supporting infantry, the up-front PAK could handle them easily enough, and they might take out a few from a larger tank unit, and prevent it from sticking around in the defended zone. The main effect on massed tanks, though, was to strip them of infantry support and button them up.

A mass of buttoned, unsupported tanks rummaging around in an unscouted enemy rear then made a fine target for counterattacking assault guns or tanks, or could be hunted at night by infantry AT teams with grenade bundles, molotovs, magnetic mines, schrecks, or fausts. If the attackers could not break through the "soft" defense someplace in the zone and re-establish both combined arms and supplies rapidly, the tanks could accomplish little, and were in serious danger if any sort of armor were available to counterattack.

The heavy weapons, including 20mm FLAK, were not expected to KO enemy armor and did not need to, for the whole defense system to work. In CM terms, a realistic number to have on one field is 2 or 4, not more. But a dozen guns of all types is perfectly reasonable in a battalion-sized fight. Just do not take all 20mm FLAK. You can take 2-4 of them, and the same of 75mm infantry guns, on-map 81mm mortars, and/or 50mm or 75mm PAK, plus a few TRPs and 75, 81, and/or 105mm FOs.

E.g. 2x20mm, 2x75mm inf, 2x81mm on-map, 2x75mm PAK, 2xTRP, 1x81mm FO, 1x105mm FO. That heavy weapons and artillery load-out costs 500 points as regulars, 40% of it is the artillery and 60% of it the direct fire stuff. In a smaller fight where the artillery budget won't fit, substitute 75mm support for 105mm and use only 1 infantry gun, for ~400 points. If you need to economize further, you can reduce the PAK to 50mm or use just one, drop the on-map 81mm mortars, etc. Defending infantry uses that sort of gun mix instead of spending points on armor and vehicles. The "armor" is provided by digging in and by hiding until the right target appears.

[Stalin's Organ]

I've seen an org for panzer-grenadiers that gives 1 20mm Flak on a h/t per infantry PLATOON, as part of that platoon....

[Username]

http://www.feldgrau.com/weaprod.html

The Germans made obver 100,000 of these 20mm type weapons. It shared ammo with aircraft weapons also I believe.

The fuze was probably SQ (superquick) and supersensitive. It HAD to be to detonate on aircraft surfaces.

In the ground role, it would certainly kick ass firing into tree lines, etc as the branches/leaves would detonate the fuze. Its ironic that US airborne troops often ran into these FlaK weapons (and 88s) and paid a terrible price. Not in the air but on the ground! As the allies closed in on germany, they would certainly see more of these weapons in the front linesss.

I bet the germans made ammo for these weapons in the 100s of millions. The round, by the way, dwarfs a 50 cal. I bet the germans used quad 20mm mounts just like the US did in Korea. The US liked the football field sized dispersion pattern of a rain of quad-50 bullets at long range (thousands of yards). I am sure the germans used these tactics on the eastern front where range presented itself. A rain of exploding 20mms coming out of the blue would terrify a defender. It would be like a mini-cluster bomb attack with no warning.

A quad 20mm targetting a tank directly would certainly blind it quickly. The constant rapid detonations and sparks/flash/smoke would make spotting (while buttoned) improbable. The effect on vision would then be eroded as vision blocks, sights, etc are ripped off.

Lewis

[Stalin's Organ]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Username:

The fuze was probably SQ (superquick) and supersensitive. It HAD to be to detonate on aircraft surfaces.

<HR></BLOCKQUOTE>

You do not want that vs aircraft - you want the shell to penetrate the surface and explode in the structure. Aircraft systems are not very robust, although the designers try their best of course.

Hence the allies had armour piercing, HE and incendiary all in a single shell - yuo don't need a lot of HE to do significant damage with fragments, and a lot of any aircraft is fuel tank and yuo don't need a lot of incendiary mix in one of those either!

[rvalle]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Franko:

Okay, I just have a couple of questions for you hardcores out there...

2. I read a historical source somewhere that stated that those 20mm guns were VERY frequent tank killers on the Eastern Front..simply because they drove Russian tank crews MAD because of the enormous banging that would result from multiple hits on a steel tank. Any truth to this? Have any historical sources?

Thanks! You geeks..I love ya.

Frank<HR></BLOCKQUOTE>

A friend and I were talking about this. He said he read an account where some Germans found themselves in front of a Russian Tank attack with no AT guns. All they had were AA guns so they opened up... all guns firing on one tank. To their amazment the tank stopped and the crew bailed, getting cut down buy the AA shells. They shifted their fire and the same happened to the other tanks.

They found a crew man alive and asked him why they bailed. He claimed that the noise was so bad that it drove them crazy. They knew they would be killed if the left the tank but HAD to get away from the noise. One crew member shot himself inside the tank. Some of them had blood coming from their ears.

I'll have to ask him where he read this at.

rv

[offtaskagain]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Username:

I bet the germans made ammo for these weapons in the 100s of millions. The round, by the way, dwarfs a 50 cal. I bet the germans used quad 20mm mounts just like the US did in Korea. The US liked the football field sized dispersion pattern of a rain of quad-50 bullets at long range (thousands of yards). I am sure the germans used these tactics on the eastern front where range presented itself. A rain of exploding 20mms coming out of the blue would terrify a defender. It would be like a mini-cluster bomb attack with no warning.

<HR></BLOCKQUOTE>

The quad .50s could be terriffying in an indirect fire support role. The last indirect weapon knocked out at Dien Bien Phu was a quad .50 that had broken up many attacks at night with a hail like Username describes.

[ 06-24-2001: Message edited by: panzerwerfer42 ]

[Username]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Stalin's Organ:

You do not want that vs aircraft - you want the shell to penetrate the surface and explode in the structure. Aircraft systems are not very robust, although the designers try their best of course.

<HR></BLOCKQUOTE>

Aircraft system are funny in that they are moving at a pretty good clip. Something like 400 ft/sec. So if you are lucky enough to actually hit a plane, and the surface is fabric or aluminum or anything for that matter; you want the shell to explode immediately. The luxury of penetrating and detonating could be a function of propogation delay of the fuze. But the round is constantly losing velocity in its upward climb, so a delay at one altitude is not the same at another.

But you really mean to tell me that its designable to have an optimal penetration of anything from a fabric wing to an aluminum fuselage?

So considering that an AA gun is firing up and losing alot of its own velocity quickly and trying to hit a very fast target, I would say that an immediate detonation is in order..

But I will always be interested in seeing documentation from a source. You have read one right?

Lewis

[Stalin's Organ]

Obviously have - FAA A&P Airframe handbooks!!

Seriously though, there weer very few fabrick surfaces by the time 20mm's weer in common usage, and quite a lot of armour plate, plus 20mm fragments are not very big and even an aluminium skin can provide significant protection for whatever lies behind.

remember that everythign you said about the shell applies to the fragments only more so, since they are inhrently of an unaerodynamic shape and low mass, so they have much less penetrative ability than the shell itself.

[Username]

sorry but you are whacky

[JasonC]

The Germans did indeed produce a large number of 20mm AA guns counted by tube, but only 18,000 single mounts and around 2,000 quad mounts were produced for the -army- as -dismounted- guns, over the whole war. Around 8,000 of the singles and 1,400 of the quads were made before 1944. There were also around 2300 heavier 37mm FLAK made for the army, most in 1943 and 1944.

20mm were also used as aircraft guns in the Luftwaffe (4 per FW-190 e.g.), on moderate numbers of Panzer IIs plus armored cars of various makes, and some on halftracks (like the SPW-250/8 in CM), and also mounted as AA on tanks (a few hundred), halftracks and trucks (a few thousand combined). The Luftwaffe also had many for close air defense of rear areas in FLAK formations, not under army control.

All told perhaps 150k -tubes- were produced, but often in multiple mounts, on aircraft or vehicles, or in rear areas. The dismount 20mm single FLAK guns for the army were only about 1/4 as common as 81mm mortars, and less common that PAK of all types by about 1/3. Still a common weapon, but not flocks of them with every infantry battalion.

As for armored panzergrenadiers (one battalion per panzer division) platoon command vehicles, they were supposed to have a 37mm PAK (a type not included in CM). Some probably used 20mm instead (SPW-250/8 e.g.), or halftrack mounted 75mm infantry guns for that matter (SPW-251/9 e.g.). The idea was any sort of heavier direct fire weapon to suppliment the MGs on the 'tracks. But this is only a matter of about a dozen vehicles in each panzer division, since it was only one battalion (occasionally two) that was mounted on 'tracks to begin with.

[gatpr]

About the aircraft issue. what about proximity fuses. They surely were not intended to penetrate!

[Username]

<BLOCKQUOTE>quote:</font><HR>Originally posted by gatpr:

About the aircraft issue. what about proximity fuses. They surely were not intended to penetrate!<HR></BLOCKQUOTE>

Prox fuzes or time fuzes are really meant for larger caliber single shot weapons. The 20mm is so small that the fuze would have to be as compact as possible. Since it is rapid fire, it is impractible to dial in an altitude. The germans did not have prox technology like the US pozit fuzes. The germans probably had a self destruct feature where the round would go off after awhile but thats really a safety issue.

The german 20mms more than likely had SQ contact fuzes.

Lewis

[Stalin's Organ]

<BLOCKQUOTE>quote:</font><HR>Originally posted by gatpr:

About the aircraft issue. what about proximity fuses. They surely were not intended to penetrate!<HR></BLOCKQUOTE>

as username said - no they weren't, but then they weren't used in 20mm cannon either! AFAIK they still aren't, because teh fragmentatino effect is jsut too small.

the 20mm relies on volume of fire to get direct hits. It then has enough mass to punch through an aircraft skin and detonate inside, where it will cause the most damage.

[JasonC]

Actually, most aircraft autocannons have the shells fused to explode after traveling some set range limit, to detonate them even if they miss their intended target. And prevent them from falling wherever. I know the 20mm in Brit aircraft did, and I've read combat reports that talk about the little white puffs in the air in dogfights.

[Andreas]

<BLOCKQUOTE>quote:</font><HR>Originally posted by JasonC:

Actually, most aircraft autocannons have the shells fused to explode after traveling some set range limit, to detonate them even if they miss their intended target. And prevent them from falling wherever. I know the 20mm in Brit aircraft did, and I've read combat reports that talk about the little white puffs in the air in dogfights.<HR></BLOCKQUOTE>

The modern Rheinmetall 20mm twin AA gun had the fuse set to 1,600m. This is to avoid having shells that missed drop down on the ground and explode amongst friendlies. The mechanism (as was explained to yours truly by our instructor) is that the reduction in shell rotation is setting the fuse off at 1,600m. The rounds are loaded with a mix incendiary/HE for maximum damage. No idea about the fuse settings in the old one, but I have a booklet at home that may have the answer.

[Username]

http://www.aircav.com/cobra/ammo20.html

sarcasm on: Would someone please have the US army contact this Stalin Organ so that he can relate the info about the delay acting 20mm fuzes?

If a 20mm goes off point detonating (like they did-see website) , The supersonic explosion would blow the fuze and chunks off the front of the shell into the aircraft. The sides of the shell would fan out splinters to about 20 feet. Given the degrees of freedom of aircraft and the various angles that shells can collide with them; a point detonation is in order.

Lewis

[Stalin's Organ]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Username:

sarcasm on: Would someone please have the US army contact this Stalin Organ so that he can relate the info about the delay acting 20mm fuzes?

If a 20mm goes off point detonating (like they did-see website) , The supersonic explosion would blow the fuze and chunks off the front of the shell into the aircraft. The sides of the shell would fan out splinters to about 20 feet. Given the degrees of freedom of aircraft and the various angles that shells can collide with them; a point detonation is in order.

<HR></BLOCKQUOTE>

Duh! When did I ever say that it was not point detonation??

now if you want to say that this ammo was used in WW2 I'd like to see the references.

Perhaps also you'd like to compare some other stuff - your web siet for modern 20mm ammo says that teh rounds have an average muzzle velocity of 3380 fps.

Compare that to, say, the 20mm Hispano Mk IIcannon used by the Brits a lot - MV of 80m/s, or about 2860fps - 85% of the mv of the modern ammo. And less for every other 20mm gun in use during WW2.

The modern ammo probably doesn't need any help penetrating aircraft skins, since it packs a lot more energy.

And where do you get the 20 feet figure from? The site says that fragments could "produce casualties" within 2 meters (6.5 feet) - no mention of damage to structures at all. But I'd expect 2m to be the maximum it might do any damage at all to a metal structure too. Of course damage to the outside of an aircraft is pretty unimportant compared to what you can get exploding teh shell inside where every fragment is going to hit something.

But hey, never mind the logic.......

[Stalin's Organ]

Right - rather than being pilloried for daring to suggest something common sense, I finally found a web site that says what I said earlier. I can't vouch for it's authority, but it's extensive and deals with Fighters, armaments and all sorts of similar stuff from WW2:

Fighter Guns

Almost halfway down the page you'll find:

<BLOCKQUOTE>quote:</font><HR>Fusing was always critical for high-explosive rounds. A too sensitive or too fast fuse would make the projectile ineffective, as it would explode when hitting the outer plating of the aircraft. A too slow fuse could also have disadvantages, in extreme cases the projectile could pass through the aircraft before exploding. It took some time to develop suitable fuses. Early British 20mm rounds were ineffective because they exploded too fast, and for some time solid AP rounds were the most used ammunition for the Hispano cannon.

<HR></BLOCKQUOTE>

[Username]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Stalin's Organ:

Duh! When did I ever say that it was not point detonation??

But hey, never mind the logic.......<HR></BLOCKQUOTE>

"It then has enough mass to punch through an aircraft skin and detonate inside, where it will cause the most damage."

You crack me up.