2cm Flak38

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davebender

1st Lieutenant
6,446
155
Jan 18, 2009
Michigan, USA
57.5kg weight. 2cm Flak38.
42.7kg weight. MG151/20.

The Flak38 is a far more powerful cannon. Did Germany consider a belt feed for this weapon? Seems to me it would make an ideal prop shaft weapon. Or perhaps put a pair in the nose of Me-110.
 
What a stupid idea! Lets take some data into account.

Project. masses: FLAK38 - 134 g, MG151/20 - 115 g.
Mussel velosity: FLAK38 - 835 m/s, MG151/20 - 780 m/s.
So we have FLAK38 mussel energy 33% more then MG151/20.
But RATE OF FIRE: MG151/20 - 800 rpm, FLAK38 - 480 rpm ONLY!!!

So we have 20% disadvantage of FLAK38 in sens of energy per min!
Comparing Q-factors we have FLAK38 TWICE allmost worse then MG151/20!!!

By the way Germans really tried to realize this idea and tried to get aviation cannon from FLAK30, it was MG C/30L. It's rate of fire was only 300-350 rpm.
 
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Better velocity incrementally reduces lead on deflection shot. You have a chance if in front of the target but no chance if behind it.. I think I want the faster round over rpm.
 
Belt feed 3cm Mk103 cannon was scaled up to produce belt feed 3.7cm Flak43. Why not scale it down to produce a high velocity 2cm weapon for use against ground targets?
 
davebender said:
Belt feed 3cm Mk103 cannon was scaled up to produce belt feed 3.7cm Flak43. Why not scale it down to produce a high velocity 2cm weapon for use against ground targets?
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Belt feed 3.7cm Flak43????

Where do you get this stuff from???

Unless you do something totally nuts, like necking down a 30-37mm round to 20mm, no 20mm round is going to be a good armor piercing round against real tank armor.

Unless you are trying to shoot armor vehicles, really high velocity isn't needed, because ground targets don't move much (need lead) compared to aircraft targets. trying to "out range" ground mounted AA guns is a useless exercise because the ground guns can always be heavier and have a more stable base ( the earth) to fire from.
 
DerAdlerIstGelandet said:
It is not necessary to call people or their ideas stupid.
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OK, sorry

Shortround6 said:
Unless you are trying to shoot armor vehicles, really high velocity isn't needed, because ground targets don't move much (need lead) compared to aircraft targets.
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And in this case it can make sense! Really for such crafts as Henshel Hs-129 for ex. I would prefer to have couple MG C/30L instead of MG 151-s that it in reality was armed by. MG C/30L with the same munitions as KwK30/38 had rather more explosive power had better armor-piercing capabilities then MG151.

So I think that Henshel Hs-129 with 2 MG C/30L would have better assault capabilities. Its the same situation that with Il-2 happened when it was armed with VYa-23-mm autocannon that was twice powerful then ShVAK.

The other case that from the end of 1942, even MG C/30L/KwK30/38 were ineffective against T-34-s so 30-mm cannons were to be needed.
 

We have the classic trade offs here. MG 151 weighs about 42kg, the MG C/30L went about 64kg and fired about 1/2 as fast. The 20 X 128 round was not enough more powerful to make up that kind of difference. In terms of muzzle energy the most 20 x 128 ammo was about as powerful as Hispano ammunition. Roughly 45-50,000 joules, The MG 151 ammo was mostly in the under 30,000 joules area and the ShVAK around 36,000 joules although it used the lightest projectiles (except for the MG 151 mine shells) so it lost striking energy the quickest over distance. The 23 x 152 fired by the VYa-23 had about 77,000 joules and with a 200 gram projectile lost the least amount of striking energy over distance. This casing was over 30mm in diameter in back of the neck and it needed a 68 kg gun to fire it. The 30 x 184B APCR round fired by the MK 103 was about 163,000 joules and the normal AP shot was 131,000 joules. And the MK 103 went about 141 KG.

As a comparison the British 2pd AT gun fired a 1,077gm shot at 853m/s for 392,000 joules. Granted it is trying to make a hole 4 times the area of a 20mm round but you get the idea. NO normal aircraft cannon was going to be much good against anything but the lightest tanks and assorted armored cars and APCs. British 2pdr Vickers aircraft cannon had 214-221,000 joules.

You are not going to get powerful (high muzzle energy) guns at light weight and high rates of fire. After a certain point high velocity guns get well into the diminishing returns category, like needed 20% or more powder for a 10% or less increase in velocity. It is not really the velocity that kills barrels but the amount of hot gases funneled through them in a given amount of time in relation to the surface area. Higher velocity 20mm guns than the Hispano or 20 X 128 need new propellants or larger, heavier cartridge cases and lots of spare barrels.
 
Unless you are trying to shoot armor vehicles, really high velocity isn't needed, because ground targets don't move much
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How do you engage soft targets @ 1,000 meters with 20mm HE rounds unless they are relatively heavy and have high muzzle velocity?
 
One need to be a hell of a marksman to hit a truck (let alone somenting smaller) with an aircraft mounted gun from 1000m.


No 20mm stuff was not going to cut vs. T-34 (even in 1941), so ditch all the guns install 2 x 30mm ASAP?
 
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One need to be a hell of a marksman to hit a truck (let alone somenting smaller) with an aircraft mounted gun from 1000m.
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I agree.

However the same weapon routinely engaged enemy infantry and vehicles from ground mounts such as this @ 1,000 meters.
 
Dave, surely you know shooting at a slow moving target, 1000 meters away, from a stationary gun platform, has little relation to the aiming problem encountered when you try to hit the same target, at the same range, and your gun platform is moving 200+ mph ?
 
And that is why an aircraft gun is not going to "out range" a ground mounted gun. The Ground mounted gun using the same ammo has got a lot better stability and will be more accurate. Trying to design and build aircraft guns to out range AA guns is a fools game.

As far as trying to "bust" tanks with 20mm guns goes, unless you are in a steep dive even relatively thin armor will stop or turn 20mm ammo. If our tank is sitting perfectly level and it's top is perfectly flat and 10mm thick a plane diving at it at a 30 degrees will find the armor acting like it was 2 1/2 to 3 times thicker than 10mm or 25-30mm thick. The shallower the dive the worse it gets. The side/rear armor was actually an easier target on many tanks. Step dives means you are firing from quite a distance away as you need room to pull out.
 
Up to September 1942.
Causes of Soviet Tank Losses, by Caliber
2.9% 105mm.
3.4% 88mm
4.7% 20mm.
10% 37mm.
10.1% 75mm.
62% 50mm. 7.5% 5cm/42. 54.3% 5cm/60.

During 1941 the Soviet Union lost about 20,500 tanks. About 960 were lost to 20mm fire.

By the end of 1941 the German Army had about 2,000 20mm weapons in service. Not all were on the Russian front. Many (probably most) 20mm weapons on the Russian front probably never encountered an enemy tank.

Flak 38 wouldn't be my first choice for an anti tank weapon. However it's readily apparent the Flak 38 could kill tanks during the first half of WWII before 30+ ton tanks became common. It could easily kill the multitude of horse drawn wagons, trucks, half tracks, Bren Carriers, artillery tractors etc. that were common during WWII. Not to mention enemy infantry.

Anyway....
Whether we like the weapon or not is beside the point. The German Army like 20mm weapons right up to the present day. So why didn't they make a belt feed version of the Flak 38 just as they made a belt feed version of the 3cm Mk101 cannon?
 
davebender said:
Up to September 1942.

2.9% 105mm.
3.4% 88mm
4.7% 20mm.
10% 37mm.
10.1% 75mm.
62% 50mm. 7.5% 5cm/42. 54.3% 5cm/60.

During 1941 the Soviet Union lost about 20,500 tanks. About 960 were lost to 20mm fire.
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True but most of those were crap tanks weren't they? T-37s, T-40s, T-60s, old T-26s and old BT series tanks. The First 3 weren't causing the Germans a lot of trouble in any case and hardly needed specialized anti-tank aircraft to take them out. The last tow were out of production and aside from mounting an effective cannon had little to recommend them (thin armor, bad layouts, few if any radios, unreliable due to age and lack of spare parts. Many of those 20,500 tanks lost were abandoned due to breakdowns not gunfire).




Yes it could but it didn't need any higher velocity to kill any of those targets. It was perfectly adequate for those targets as it was.

davebender said:
Anyway....
Whether we like the weapon or not is beside the point. The German Army like 20mm weapons right up to the present day. So why didn't they make a belt feed version of the Flak 38 just as they made a belt feed version of the 3cm Mk101 cannon?
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It is not a question of liking the weapon or not, it is a matter of trying to turn it into something it was not, or thinking that with just a FEW improvements it could be boosted into a different weapon class.

Good AA guns are not necessarily good aircraft guns. The AA gun can be heavier (much heavier at times) and can use heavier ammo.

20mm guns are good for a certain range of targets and no amount of tinkering with powder charges, case size or trick projectiles is going to turn them into 35-40mm guns.

As far as designing a belt feed for it, maybe it could be done or maybe it required too much effort even if it could be done.

The Hispano seemed to have an excess of recoil energy available. Engine mounted guns did not have muzzle breaks but drum feed non-engine mounted guns did. Muzzle breaks were removed form guns fitted with belt feeds and the recoil energy used to operate the belt feeder. Maybe the Flak 38 had extra energy and maybe it didn't, Maybe with a lighter barrel and lighter bolt it would have, I don't know. But if the engineers are trying to turn the Flak 38 into a belt feed gun what else aren't they doing?
 
if the engineers are trying to turn the Flak 38 into a belt feed gun what else aren't they doing?
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WWII Germany was the world leader in automatic weapons design. German machineguns and automatic cannon up to 55mm size were world class. Making a belt feed cannon chambered for the 20 x 138mmB cartridge shouldn't be much of a chore for a nation with so much automatic weapons expertise. Unless there's something specific about that cartridge type which makes it incompatible with belt feed.
 
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