German logistics, purchase programs and war booty, reality and alternatives 1935-43 (1 Viewer)

[tomo pauk]

That's not to say that using compressed syngas as a vehicle fuel behind the lines wouldn't have been possible. The price would be very short range, but OTOH you wouldn't need the hassle of carrying and operating a wood or coal gasifier on the back of the vehicle.

The big facilities to make these gasses would've been probably easier, faster and cheaper to make than the tens of thousands of the gas generators that Germans made back in ww2, due to the economy of scales.

 

[z42]

The big facilities to make these gasses would've been probably easier, faster and cheaper to make than the tens of thousands of the gas generators that Germans made back in ww2, due to the economy of scales.

Maybe? There's an economy of scale in mass producing smaller trinkets on a production line as well. See the multitude of massively over budget and schedule megaprojects, such as any Western nuclear power plant in the past 30 years.

Moreover, there's also the issue that with a strategy centered around centralized gas generators and storing the gas for use in vehicles, you need compressors and high-pressure gas containers. Which sounds more expensive than a vehicle mounted gasifier which is a basically atmospheric pressure thing made from thin sheet metal. But I don't know, maybe the added convenience makes it worth the effort?

Also, with centralized gas generators maybe you can have more extensive gas filtering things and professionals running the show, so maybe it would be possible to run on the plentiful and cheap lignite rather than wood chips or bituminous coal that the vehicle mounted gasifiers needed?

 

[tomo pauk]

Moreover, there's also the issue that with a strategy centered around centralized gas generators and storing the gas for use in vehicles, you need compressors and high-pressure gas containers. Which sounds more expensive than a vehicle mounted gasifier which is a basically atmospheric pressure thing made from thin sheet metal. But I don't know, maybe the added convenience makes it worth the effort?

Perhaps he best bet for them would've been to press on with both systems - IOW both the big facilities and on-vehicle installations?

 

[tomo pauk]

Back to the things going 'boom'.

Come 1941, there were thousands upon thousands of 37mm barreled non-Flak weapons in German possession, be these 3.7cm pak (14+ thousands of 3.7cm pak in Heer possession at June 1st 1941), or the different weapon of same nominal caliber captured in CZ, Poland, France etc. Germans were aware of the deficiencies of the 37mm caliber in it's primary role even before ww2 started, so the 5cm weapons were in pipeline back then, and were being introduced by late 1940. So we have, by same date (July 1s 1941) 1206 of pak 38 at Heer, as well as hundreds of the Pz-III armed with 5cm gun.
In the same time, the production of the automatic 3.7cm Flak is pathetic, and rate of fire of the naval 3.7cm Flak is pathetic, too.

Several cunning ideas:

- A higher-power 3.7cm automatic gun design for all of the German surface-based anti-aicraft needs; if not as powerful as the 4cm Bofors, to be at least as powerful as the Soviet 37mm, that was propelling the 732g shell at 880 m/s (210g of propellant, vs. the 3.7cm Flak 18/36/43 with 185g of propellant*, and the M42 with 175g; the Navy's 3.7cm pre-war flak used mind-boggling 365g of propellant). Round this out to 750g shell at 900 m/s (230-250g of propellant?) and they can have themselves a fine AA gun. A pre-war design should have the RoF similar to what the Flak 18 had, while later models should up it somewhat. Ideally, the light Pak should've been also made around this cartridge, but don't over-produce the Pak.
(granted, all of this was suggested earlier by your's truly)

- A baby 37mm gun, tailored at 1st to be an airborne gun, possibly something made instead of the MK 101. Main emphasis towards being suitable for motor-cannon installation, ie. no protrusions to mess with the required blast tube diameter - scaling-up of the working principle of the Flak 30 will do. At about 150 kg for the 'naked' gun. Half of the propellant weight of it's big brother (~120g?), aiming to produce the 'N-37 minus' or a 'MK-101/37' in the 1st go (200-250 rd/min, 750g shell at 600++ m/s, and/or a 620-630g shell at 680-700 m/s?). N-37 used 127 g of propellant, the MK 101 used 110g. Rimless ammo, vs. rimmed for the big brother. Same as with the 3cm guns, make the Mine shell; historically, once the M-shell was made for the 37mm, it weighted 550g. A 550g shell should have the higher MV, probably close to 750 m/s? It will take perhaps 1 such shell to bring down most of the 2-engined A/C of the day, and max of 3 for a 4-engined bomber? Making the baby 37mm gun with the higher RoF by 1943-ish should not be a problem.

- Here is the most cunning part: have the foresight to use the 37mm non-Flak barrels as a source of barrels for the baby automatic 3.7cm gun, moreso since 37mm barrels are in production basically everywhere. Yes, some ammo types will not suit some barrels perfectly, so experiment a bit with the loadings. Use the 'land' carriages to mount the more substantial guns.

*for the 'normal' ammo; the cored ammo, usually for the BK 3.7cm, used 260g

 

[Zmauky]

As much as I like the idea of a small aircraft 37mm gun, it's probably a better idea to skip the 37mm AT gun altogether (or at least limit production).
Mass production of the Pak 36 started in 1936 of course, but at that time (since 1934) the 7.5cm Selbstfahrlafette L/40.8 was also being developed.

Pz.Sfl. II - Wikipedia

en.wikipedia.org

Or

7,5 cm Selbstfahrlafette L/41 Modell 2

poll I would like to suggest the 7,5 cm Selbstfahrlafette L/41 Modell 2 It would be a unique playstile for the german tree as it combines firepower with mobility at the lower ranks in for of a Mobile Light Tank Rank 3 Br 3.3. It carries a 7,5 cm Kanone L/41 which is a more powerful gun than the...

forum.warthunder.com

So if it had been adopted (as a panzerjager component of armored units) I somehow don't think the infantry would have received the (in that case much weaker) Pak 36 - or at least not in those quantities. I know, the requirement was that the AT gun could be moved by the crew, but I think it would have been adopted at least as a heavy AT component. In that case, the Pazer III probably wouldn't even start with a 37 mm gun (and since the L40.8 is a relatively small gun, it's possible that it would fit in a tank turret instead 50 mm.
Likewise, why would a Panzer IV have a short 75 when it can get an L40.8?

Speaking of which (not to provoke a debate and/or Pz III / Pz IV) why couldn't the PZ III be a couple of centimeters wider so that the III and IV have exactly the same turret? (and not that III has the same one, only a little squeezed in the wash)

 

[Elan Vital]

Back to the things going 'boom'.

Come 1941, there were thousands upon thousands of 37mm barreled non-Flak weapons in German possession, be these 3.7cm pak (14+ thousands of 3.7cm pak in Heer possession at June 1st 1941), or the different weapon of same nominal caliber captured in CZ, Poland, France etc. Germans were aware of the deficiencies of the 37mm caliber in it's primary role even before ww2 started, so the 5cm weapons were in pipeline back then, and were being introduced by late 1940. So we have, by same date (July 1s 1941) 1206 of pak 38 at Heer, as well as hundreds of the Pz-III armed with 5cm gun.
In the same time, the production of the automatic 3.7cm Flak is pathetic, and rate of fire of the naval 3.7cm Flak is pathetic, too.

Several cunning ideas:

- A higher-power 3.7cm automatic gun design for all of the German surface-based anti-aicraft needs; if not as powerful as the 4cm Bofors, to be at least as powerful as the Soviet 37mm, that was propelling the 732g shell at 880 m/s (210g of propellant, vs. the 3.7cm Flak 18/36/43 with 185g of propellant*, and the M42 with 175g; the Navy's 3.7cm pre-war flak used mind-boggling 365g of propellant). Round this out to 750g shell at 900 m/s (230-250g of propellant?) and they can have themselves a fine AA gun. A pre-war design should have the RoF similar to what the Flak 18 had, while later models should up it somewhat. Ideally, the light Pak should've been also made around this cartridge, but don't over-produce the Pak.
(granted, all of this was suggested earlier by your's truly)

- Here is the most cunning part: have the foresight to use the 37mm non-Flak barrels as a source of barrels for the baby automatic 3.7cm gun, moreso since 37mm barrels are in production basically everywhere. Yes, some ammo types will not suit some barrels perfectly, so experiment a bit with the loadings. Use the 'land' carriages to mount the more substantial guns.

*for the 'normal' ammo; the cored ammo, usually for the BK 3.7cm, used 260g

As much as I like the idea of a small aircraft 37mm gun, it's probably a better idea to skip the 37mm AT gun altogether (or at least limit production).
Mass production of the Pak 36 started in 1936 of course, but at that time (since 1934) the 7.5cm Selbstfahrlafette L/40.8 was also being developed.

Pz.Sfl. II - Wikipedia

en.wikipedia.org

Or

7,5 cm Selbstfahrlafette L/41 Modell 2

poll I would like to suggest the 7,5 cm Selbstfahrlafette L/41 Modell 2 It would be a unique playstile for the german tree as it combines firepower with mobility at the lower ranks in for of a Mobile Light Tank Rank 3 Br 3.3. It carries a 7,5 cm Kanone L/41 which is a more powerful gun than the...

forum.warthunder.com

So if it had been adopted (as a panzerjager component of armored units) I somehow don't think the infantry would have received the (in that case much weaker) Pak 36 - or at least not in those quantities. I know, the requirement was that the AT gun could be moved by the crew, but I think it would have been adopted at least as a heavy AT component. In that case, the Pazer III probably wouldn't even start with a 37 mm gun (and since the L40.8 is a relatively small gun, it's possible that it would fit in a tank turret instead 50 mm.
Likewise, why would a Panzer IV have a short 75 when it can get an L40.8?

Speaking of which (not to provoke a debate and/or Pz III / Pz IV) why couldn't the PZ III be a couple of centimeters wider so that the III and IV have exactly the same turret? (and not that III has the same one, only a little squeezed in the wash)

The origins of the 37mm PaK and its ballistics go at least as far back as 1927, with low rate production starting in 1930. It is unlikely that the barrel would be suitable for AA guns.

The Germans dabbled with longer-barreled PaK 36 (L60 and L65) as well as new 37mm guns (L64 and L70) during the 30s and 75/77mm guns in the 1920s and 30s, but remained too cautious to order a mix of different guns and ammunition. In hindsight it was probably a worthwhile risk to go with these options anyway, with either a hi-lo mix of converted 75/77mm guns at the high end and PaK 36 at the low end to be followed by the 50mm ASAP, just like the French mix of 25 and 75mm and then 47mm guns.

The question of new or longer barrel 37s would be analogous to the British/American approach of high velocity low caliber guns only (initially) or the Soviet move of developping a long barrel 45mm to replace the 32-K.
The matter of a long barrel 75 in the Pz IV from the start would require a different weight limitation beyond the 18 tonnes initially allowed.

 

[tomo pauk]

The origins of the 37mm PaK and its ballistics go at least as far back as 1927, with low rate production starting in 1930. It is unlikely that the barrel would be suitable for AA guns.

Note that I've not suggested that the historical 37mm ATG barrel is repurposed in an AA weapon, but in an airborne gun of moderate ballistics.

 

[z42]

- A higher-power 3.7cm automatic gun design for all of the German surface-based anti-aicraft needs; if not as powerful as the 4cm Bofors, to be at least as powerful as the Soviet 37mm, that was propelling the 732g shell at 880 m/s (210g of propellant, vs. the 3.7cm Flak 18/36/43 with 185g of propellant*, and the M42 with 175g; the Navy's 3.7cm pre-war flak used mind-boggling 365g of propellant). Round this out to 750g shell at 900 m/s (230-250g of propellant?) and they can have themselves a fine AA gun. A pre-war design should have the RoF similar to what the Flak 18 had, while later models should up it somewhat.

The Flak 18/36/43 might not be the 'gold standard' that the 40mm Bofors turned out to be, but is it really bad enough that a new design is warranted? Or just build more of them (instead of, say, the quad 20mm?), and maybe add better fire control (gun-laying radar might be bordering on possible in WWII, Allies used them at least for shooting down V1's..)?

- A baby 37mm gun, tailored at 1st to be an airborne gun, possibly something made instead of the MK 101. Main emphasis towards being suitable for motor-cannon installation, ie. no protrusions to mess with the required blast tube diameter - scaling-up of the working principle of the Flak 30 will do. At about 150 kg for the 'naked' gun. Half of the propellant weight of it's big brother (~120g?), aiming to produce the 'N-37 minus' or a 'MK-101/37' in the 1st go (200-250 rd/min, 750g shell at 600++ m/s, and/or a 620-630g shell at 680-700 m/s?). N-37 used 127 g of propellant, the MK 101 used 110g. Rimless ammo, vs. rimmed for the big brother. Same as with the 3cm guns, make the Mine shell; historically, once the M-shell was made for the 37mm, it weighted 550g. A 550g shell should have the higher MV, probably close to 750 m/s? It will take perhaps 1 such shell to bring down most of the 2-engined A/C of the day, and max of 3 for a 4-engined bomber? Making the baby 37mm gun with the higher RoF by 1943-ish should not be a problem.

Not sure this makes sense? Aircraft were the 'rocket science' of the time; airframes were expensive, and so were engines and pilots. Does it make sense to use a sub-optimal gun just in order to be able to reuse some old 37mm barrels?

- Here is the most cunning part: have the foresight to use the 37mm non-Flak barrels as a source of barrels for the baby automatic 3.7cm gun, moreso since 37mm barrels are in production basically everywhere. Yes, some ammo types will not suit some barrels perfectly, so experiment a bit with the loadings. Use the 'land' carriages to mount the more substantial guns.

Another suggestion for a 'baby 37mm' to reuse old 37mm barrels: Make a lightweight cheap relatively low-velocity (200-500 m/s?) 37mm auto-cannon, mount it on half-tracks, or on otherwise obsolete tank chassis, or even truck roofs, to be used for spraying HE on soft targets? A bit like the post war Mk 19 grenade launcher - Wikipedia

 

[tomo pauk]

The Flak 18/36/43 might not be the 'gold standard' that the 40mm Bofors turned out to be, but is it really bad enough that a new design is warranted? Or just build more of them (instead of, say, the quad 20mm?), and maybe add better fire control (gun-laying radar might be bordering on possible in WWII, Allies used them at least for shooting down V1's..)?

The main problem the German automatic 37mm AA guns had was probably that of low availability vs. the 20mm. So I'd agree on making more of them, even if the trade-off is making less of the 20mm stuff.

Not sure this makes sense? Aircraft were the 'rocket science' of the time; airframes were expensive, and so were engines and pilots. Does it make sense to use a sub-optimal gun just in order to be able to reuse some old 37mm barrels?

Germans reckoned that a 4-mot required 20 hits of the 20mm M-shell to bring it down, 5 hits of 30mm M-shell, and just one 55mm M-shell (guarantee?; the 50mm mine shells were judged as not able to 1-shot the B-17, baring a lucky shot in the pilot cabin?). A 37mm cannon might require just 3?

Another suggestion for a 'baby 37mm' to reuse old 37mm barrels: Make a lightweight cheap relatively low-velocity (200-500 m/s?) 37mm auto-cannon, mount it on half-tracks, or on otherwise obsolete tank chassis, or even truck roofs, to be used for spraying HE on soft targets? A bit like the post war Mk 19 grenade launcher - Wikipedia

One Pak barrel for making two grenade launchers' barrels?

 

[z42]

but at that time (since 1934) the 7.5cm Selbstfahrlafette L/40.8 was also being developed.

Thanks; I wasn't aware of this gun. But yes, as I've mentioned before (maybe in this thread even?) I think Germany would have needed something similar to the ubiquitous Russian and American medium velocity 75/76mm guns; big enough to have a decent HE load, high enough velocity to make hitting a moving vehicle or a point target at uncertain range at least somewhat feasible.

Likewise, why would a Panzer IV have a short 75 when it can get an L40.8?

Speaking of which (not to provoke a debate and/or Pz III / Pz IV) why couldn't the PZ III be a couple of centimeters wider so that the III and IV have exactly the same turret? (and not that III has the same one, only a little squeezed in the wash)

The matter of a long barrel 75 in the Pz IV from the start would require a different weight limitation beyond the 18 tonnes initially allowed.

The Germans might have had a better idea of a good tank doctrine early in the war than pretty much anyone else, but given the small size of those early tanks there were some hard choices to make, resulting in needing separate AT tanks with the high-velocity 37mm guns and separate support tanks with the low velocity 75mm guns.

It's sort-of bordering-on-the-possible to design the Pz III just a little bit larger, in order to comfortably fit a medium-velocity (say, 600-700 m/s MV) 75mm gun like the above mentioned L/40.8, and then not need a separate Pz IV support tank at all (instead design a true next-generation general purpose tank with, say, the 88L56).

 

[z42]

Germans reckoned that a 4-mot required 20 hits of the 20mm M-shell to bring it down, 5 hits of 30mm M-shell, and just one 55mm M-shell (guarantee?; the 50mm mine shells were judged as not able to 1-shot the B-17, baring a lucky shot in the pilot cabin?). A 37mm cannon might require just 3?

I'm definitely in the 'MOAR oomph' school of fighter gun size, but even that has limits. You pay a price in weight of the gun and ammo, RoF, recoil, and most likely low MV. Given that it's likely you have to deal with fighters as well, I suspect a 37mm is overkill, in the sense a smaller shell is likely to one-hit kill a single engined fighter just as well, but you still have to pay the weight and RoF and low MV penalty of carrying such a big gun.

(Without going too far off-topic, I believe the WWII sweet spot would have been somewhere around a 200-250g shell with a MV of 700-800 m/s. RoF as high as you can feasibly make it, of course.)

One Pak barrel for making two grenade launchers' barrels?

Yes, or just going by the length maybe even three? Though the bottom part of a 37mm PAK barrel is certainly needlessly thick for such a low-velocity gun? Machine it down, or just live with barrels of different weight?

 

[tomo pauk]

The Germans might have had a better idea of a good tank doctrine early in the war than pretty much anyone else, but given the small size of those early tanks there were some hard choices to make, resulting in needing separate AT tanks with the high-velocity 37mm guns and separate support tanks with the low velocity 75mm guns.

It's sort-of bordering-on-the-possible to design the Pz III just a little bit larger, in order to comfortably fit a medium-velocity (say, 600-700 m/s MV) 75mm gun like the above mentioned L/40.8, and then not need a separate Pz IV support tank at all (instead design a true next-generation general purpose tank with, say, the 88L56).

The APHE shell was part of the normal combat load of the Pz-IV, and the short 75mm was the best hole-puncher among what the German tanks had before July 1940.
If a tank a bit larger than the Pz-III is wanted, the Pz-IV was already that, and was available earlier than the -III, despite the nomenclature.
I'm all for a 600-700 m/s 75mm gun on the Pz-IV ASAP.
The Pz-IV shared the shortcoming of the 37mm Flak, namely that of a single source until well into ww2, meaning that numbers' produced was modest until well into 1941.

Me, I'd have the Pz-I to be armed with a 20mm gun, and the Pz-II with a 37mm gun. Some re-hash of the internals will be needed, though.

I'm definitely in the 'MOAR oomph' school of fighter gun size, but even that has limits. You pay a price in weight of the gun and ammo, RoF, recoil, and most likely low MV. Given that it's likely you have to deal with fighters as well, I suspect a 37mm is overkill, in the sense a smaller shell is likely to one-hit kill a single engined fighter just as well, but you still have to pay the weight and RoF and low MV penalty of carrying such a big gun.

Germans tried to have a 140 kg MK 101 and 103 as an airborne gun for air fighting. It was not a succes due to the under-wing installation being too heavy and too draggy on the Fw 190, and could not fit in the Bf 109 as a motor gun. The 103M (reworked to fit as a motor gun) was to be installed in the latest Bf 109s, Ta 152s and Do 335s. LW was willing to pay the price.

My idea is that the light 37mm gun is made instead of these 30 mm guns, trading MV for shell weight, and that from get-go is tailored as a motor cannon. As in case with the MK 103M, the cowl guns will have to go on the Bf 109.

(Without going too far off-topic, I believe the WWII sweet spot would have been somewhere around a 200-250g shell with a MV of 700-800 m/s. RoF as high as you can feasibly make it, of course.)

A 25mm gun probably provides for that, while still being compact enough to fit not just as a motor cannon, but also as a wing gun on the Fw 190.

Yes, or just going by the length maybe even three? Though the bottom part of a 37mm PAK barrel is certainly needlessly thick for such a low-velocity gun? Machine it down, or just live with barrels of different weight?

Germans being Germans, they would've probably machined off the extra barrel thickness.

 

[Shortround6]

The 37mm aircraft guns were sort of a dead end in WW II. Things see-sawed back and forth during the 30s and WW II.
There are a lot of things to consider and they often are in conflict with each other.
as far a a single shot goes the 37mm does have a huge advantage. Japanese were using 475g shells were were among the lightest 37mm shells built. French got up to an 875g shell in a surface AA gun but that gun was very, very heavy.
Heaviest shell WW II airborne automatic 37mm seems to have been the Soviet NS-37 gun. 735g(?)
Roughly 6 times the weight of a 20mm shell, but now we hit the conflicts. The NS-37 weighs 160-170kg which is 4-5 times heavier than the smaller 20mm guns and almost 3 times heavier than a 20mm Hispano.
The other conflict is the rate of fire. The NS-37 fired at about 240-260rpm which is around 1/2 or less than most WW II 20mm guns.
The weight of fire in lbs/kilos per second for the weight of the installed gun does not look good.
Granted a single hit is devastating.
BUT
What is the chance of getting that hit?
The Soviet NS-27 was a pretty good WW II aircraft gun for a 37mm.
The American M4 was 96kg, fired at 140-150rpm and it's shell was only 610g and had a 610m/s velocity, about 20% faster than the MK 108.
The Japanese Ho-204 was 130kg and fired at an impressive 400 rpm but shell was only 475g and had a 710m/s velocity.

German 37mm aircraft gun is going to fall into that area.
Getting a high rate of fire requires a heavy gun of low shell weight and low velocity.
Keeping the gun weight low requires low power and/or low rate of fire.
Recoil effect on the aircraft is going to large. Burst fire is going to throw the aim off.
Low velocity has a similar (but not as bad) problem as the MK 108.

The airborne 37mm gun for the Germans might be effective against the allied 4 engine bombers, it will be less effective against faster, more maneuverable targets.
If you build a gun that is significantly less powerful than the 3.7cm gun under the Stuka or Hs 129 you are much less effective against tanks.
The existing 20mm guns work well against early Soviet light tanks, armored cars and trucks. They will also work well against lend lease 1/2 tracks.

Now as far a a ball park on the 37mm projectile goes, you need a 410g projectile to equal the sectional density of a 120 gram 20mm projectile, that means your 37mm projectile is just about as long as the 20mm projectile which leaves you with a short stumpy projectile. Lousy aerodynamics/streamlining. You can tweak that a bit with a sharper nose.

 

[tomo pauk]

BUT
What is the chance of getting that hit?
The Soviet NS-27 was a pretty good WW II aircraft gun for a 37mm.
The American M4 was 96kg, fired at 140-150rpm and it's shell was only 610g and had a 610m/s velocity, about 20% faster than the MK 108.
The Japanese Ho-204 was 130kg and fired at an impressive 400 rpm but shell was only 475g and had a 710m/s velocity.

Seems like all of these guns stood a much better chance to hit than the MK 108, especially if the target is at beyond white-of-their-eyes distance.
If something like the Ho 204 gun can be made as a motor cannon (and it should, looks a lot like what the MK 103 asked for), it would've been excellent on a Bf 109.

The other conflict is the rate of fire. The NS-37 fired at about 240-260rpm which is around 1/2 or less than most WW II 20mm guns.
The weight of fire in lbs/kilos per second for the weight of the installed gun does not look good.

How good is a single 20mm gun (pick the best one there was in ww2) in killing the 4-engined bombers?

If you build a gun that is significantly less powerful than the 3.7cm gun under the Stuka or Hs 129 you are much less effective against tanks.

Use the 'normal' 37mm guns for tank busting.

 

[tomo pauk]

A not-so-baby 37mm as a Flak might've been useful to the Germans, again with thousands of 37mm AT guns being all but obsolete by 1941.
Soviet post-war (1946) N-37 fired a ~735g shell at 670 m/s, using 127 g of propellant (ie. about 65% of what the 37mm pak or flak usually used, or about 60% of what the Soviet 37mm AA used), with RoF similar to that of the MK 103, and was very light, barely above 100 kg. Shorter barrel than the 37mm pak.

Germans might've opted for the cartridge that shoots the Mine shell, 550g (weight of the historical M-shell), up to perhaps 600g? RoF need to be toned down vs. the N-37 (under 200 rd/min?), since there is no high speed cooling air to help out. Using just ~130g of propellant, so that barrels that were not designed to fire at such high RoF can have a reasonably long life. Same outer dimensions of the ammo, so there is less work to do with barrel, and can also use the cored AP shot from the Pak in case of emergency.
Probably above 750 m/s might've been achieved, if not close to 800 m/s with the 550g M-shell?

As a Flak, there is no need to go very light, 120-130 kg is not too heavy, even 150 kg is passable. One Flak could be installed on vehicles that the big 37mm brother cannot and single 20mm is too weak (Pz-38(t) base, Pz-III), while twinned guns are still an option for the towed mounts and Pz-IV.

The 37mm aircraft guns were sort of a dead end in WW II. Things see-sawed back and forth during the 30s and WW II.

A bit about this.
37mm guns, at least the more powerful types, were still useful well past ww2 if paired with then-modern fire control systems. Aircraft hit with a 700-800g shell will be in big problems, it will not matter that it is fired form a boring gun.
That the 37mm AA gun was not popular in the West post ww2 had a lot to do with the 40mm Bofors being ubiquitous, and that Germany and Italy - the main users of 37mm AA there - were now in shambles. Soviets dropped the ball with not adopting the Yenisei system in the 1960s, opting for the SP 57mm gun (no radar) and Shilka (high RoF, but short range).

 

[Shortround6]

Seems like all of these guns stood a much better chance to hit than the MK 108, especially if the target is at beyond white-of-their-eyes distance.
If something like the Ho 204 gun can be made as a motor cannon (and it should, looks a lot like what the MK 103 asked for), it would've been excellent on a Bf 109.

Problem is you have to get into "white-of-their-eyes distance" with the 37mm gun in order to have decent chance of getting a hit.

How good is a single 20mm gun (pick the best one there was in ww2) in killing the 4-engined bombers?

It should not be a single 20mm gun vs ???
from a weight stand point you can get 2-4 20mm guns for each 37mm cannon and since each 20mm cannon is firing 3-4 times faster than all but the Ho 204 gun you have a much better/higher number of hits per second of firing time.

Bringing in post war guns (better metallurgy and better propellants) also opens up the discussion to better construction of airframes. I have no idea WHY Messerschmitt could not have mounted 20mm guns in the wings of the Bf 109F and Gs. They were doing it on the Es and Hispano managed to put 20mm Hispano guns in the wings of the postwar Spanish 109s. Perhaps the Germans could have put MG 151s in each wing instead of under the wings. Helps with drag but not so much with weight and roll.

For an aircraft gun system we have to look at the weight of the system (number of guns and amount of ammo installed in the aircraft) and the rates of fire and the chances of getting hits. The last is quite variable and lot can depend on the sights/fire control systems and the training. Germans estimated that their pilots could get 2% hits. Now give them American 37mm M4 guns. Using a very crude estimate of the US 37mm shell being 6 times as effective as a German 20mm we need 3-4 hits to bring down a B-17. With 30 rounds in each plane for it's 37mm gun we seem to need 5 planes to get 3 hits and 6.6 planes to get 4 hits.

This seems to a lot less effective than using 3 109s using 3 20mm guns each to get over 1000 round into the air.
Granted I used less than best example 37mm.
But I was using a 608g projectile. Using a 475g projectile means you may need 4-5 hits which means you need a faster firing 37mm gun.

A real problem with the slow firing guns is that you only get a few rounds fired in each attack run. The 30 rounds on the US M4 needs 12.5 seconds to be fired.
The interceptor is not firing from a fixed position/range. In 3 seconds a 600kph fighter covers 400 meters, now fast is the target moving (distance) and it what direction relative to the interceptor. The point of aim used at the beginning of the burst is not the same as is needed 3 seconds later. Many pilots aimed a little bit off to start and swept/walked their fire across the target. Pease forget about watching the tracers, at longer ranges that tells the pilot where he should have been aiming 0.5-1.0 seconds ago. Throw in reaction time (0.25 seconds?) and time of flight for the rounds fired after the correction (fired at a closer distance) and chances don't get much better.
Accounts of the Soviet fighters using their powerful 37mm guns some times claim they were used as single shot repeaters. Recoil from the first shot disturbed the aim too much for a fast 2nd shot or burst. Now a tail chase might suit a Yak vs He 111 or Ju-88 very well, no tail guns on the German bombers and only a weak 13mm or 2-3 7.9mm guns pointing at pursuers (and some needing some tail waggles?) instead of the 2-4 .50 guns of the American planes. German were trying to get away from tail chases. They could shoot down B-17s that way but they lost a lot of 109s doing that. The head on attacks give a high closure rate (less time to aim/fire) but a better survival rate. But using a single, slow firing gun?
The MK 108 at least fired quickly.

The German mine shell was not a panacea. It gave a high MV but it also slowed down quicker than normal projectiles. Good if you are shooting a "white-of-their-eyes distance" but not so good if you try the "stand off out side the range of the defensive guns" plan. That was rarely a good plan in practice anyway. Distance shooting accuracy against a stationary target decreases with the square of the distance, against moving targets it decreases with the cube of distance. You need really, really good fire control, really good.

One wonders what the results of increasing the German pilot's hit rate would have been. 30 hits per 1000 round fired instead of 20? And what the needed training would have been?

 

[tomo pauk]

Problem is you have to get into "white-of-their-eyes distance" with the 37mm gun in order to have decent chance of getting a hit.

Not if you have some kind of decent MV. Eg. 700 m/s is far better than Mk 108's 500 m/s.
Germans reckoned that MK 103 have had double the chance to hit vs. the MK 108; granted that is 860 m/s (M-shell) vs. 500.

It should not be a single 20mm gun vs ???
from a weight stand point you can get 2-4 20mm guns for each 37mm cannon and since each 20mm cannon is firing 3-4 times faster than all but the Ho 204 gun you have a much better/higher number of hits per second of firing time.

From the Bf 109 standpoint, it is mostly about how much a power has the motor cannon, since going to gondola 20mm guns have had a bad impact on speed, RoC and maneuverability. The more powerful the motor cannon, the better.
For fighting the 4-engined bombers, one 30mm shell hit was worth 4 20mm, we can safely assume that one 37mm hit is worth even more. pointing out even more towards the 109 affinity to wards a more punchy single cannon. One bigger cannon might also be cheaper to make that 3 smaller cannons, and same for the respective ammo load.
Yes, multiple 20mm guns will be better against smaller and more maneuverable targets, like fighters.

Bringing in post war guns (better metallurgy and better propellants) also opens up the discussion to better construction of airframes. I have no idea WHY Messerschmitt could not have mounted 20mm guns in the wings of the Bf 109F and Gs. They were doing it on the Es and Hispano managed to put 20mm Hispano guns in the wings of the postwar Spanish 109s. Perhaps the Germans could have put MG 151s in each wing instead of under the wings. Helps with drag but not so much with weight and roll.

It is not like the N-37 was from the 1960s or so. Development begun during the ww2.
Yes, not going with internal wing cannons on the 109 past the Emil was a mistake.

For an aircraft gun system we have to look at the weight of the system (number of guns and amount of ammo installed in the aircraft) and the rates of fire and the chances of getting hits. The last is quite variable and lot can depend on the sights/fire control systems and the training. Germans estimated that their pilots could get 2% hits. Now give them American 37mm M4 guns. Using a very crude estimate of the US 37mm shell being 6 times as effective as a German 20mm we need 3-4 hits to bring down a B-17. With 30 rounds in each plane for it's 37mm gun we seem to need 5 planes to get 3 hits and 6.6 planes to get 4 hits.

This seems to a lot less effective than using 3 109s using 3 20mm guns each to get over 1000 round into the air.
Granted I used less than best example 37mm.
But I was using a 608g projectile. Using a 475g projectile means you may need 4-5 hits which means you need a faster firing 37mm gun.

The M4 was among the least powerful, not the 'best example'.
Germans making the MK 101 and then 103 as motor cannons and around a less powerful 37mm instead of the high power 30mm ammo would've gotten themselves a high-RoF gun one after another, with greater production numbers than the 30 mm pieces, and still with more than decent ballistics.
A 37mm take on the MG FFM / API idea should've also worked, as it worked for the MK 108. With a 550-600g Mine shell, it will take perhaps 3 (2 if you're (un)lucky?) to kill a bomber.

IIRC Germans reckoned that their pilots were capable for landing 5% of hits on a 4-engined bomber, not just 2%. Granted, going too low with the MV will skew that %-age down.

Accounts of the Soviet fighters using their powerful 37mm guns some times claim they were used as single shot repeaters. Recoil from the first shot disturbed the aim too much for a fast 2nd shot or burst. Now a tail chase might suit a Yak vs He 111 or Ju-88 very well, no tail guns on the German bombers and only a weak 13mm or 2-3 7.9mm guns pointing at pursuers (and some needing some tail waggles?) instead of the 2-4 .50 guns of the American planes. German were trying to get away from tail chases. They could shoot down B-17s that way but they lost a lot of 109s doing that. The head on attacks give a high closure rate (less time to aim/fire) but a better survival rate. But using a single, slow firing gun?

With 200+ rd min on the "MK 101/37", and 400 on the "MK 103/37", the RoF seems good enough.
Also less powerful than the wartime NS-37 (that was one of things the Soviets changed with the N-37).

The German mine shell was not a panacea. It gave a high MV but it also slowed down quicker than normal projectiles. Good if you are shooting a "white-of-their-eyes distance" but not so good if you try the "stand off out side the range of the defensive guns" plan. That was rarely a good plan in practice anyway. Distance shooting accuracy against a stationary target decreases with the square of the distance, against moving targets it decreases with the cube of distance. You need really, really good fire control, really good.

At sea level, the 117g HE shell from a MG FFM needed 1.080 seconds to travel to the 1st 500m, the 92g M-shell needed 1.093. That is about 1% difference, or, in the words of late Paul Harrell, not enough of a difference to make a difference.

One wonders what the results of increasing the German pilot's hit rate would have been. 30 hits per 1000 round fired instead of 20? And what the needed training would have been?

A 50% improvement of the chance to hit improvement probably will not happen without the introduction of the computing gunsight.

 

[Shortround6]

Not if you have some kind of decent MV. Eg. 700 m/s is far better than Mk 108's 500 m/s.
Germans reckoned that MK 103 have had double the chance to hit vs. the MK 108; granted that is 860 m/s (M-shell) vs. 500.

For WW II 37mm guns and the German 30mm at the end.
Gun........................................shell weight....................MV m/s...........................Joules....................gun weight/KG....................rate of fire
Japanese Ho-203.................475.....................................570................................77,200..............................89.......................................120
US M4......................................608.....................................610..............................113,000..............................96.................................140-150
US M10...................................608.....................................610..............................113,000........................... .109................................150-170 (belt feed)
Japanese Ho-204................475.....................................710...............................120,000............................130.....................................400
Soviet NS-37.........................735....................................810................................285,000.......................160-170............................240-260
Soviet N-37............................735....................................690................................175,000.............................103...............................400-430
MK 108.....................................330...................................505...................................42,100..............................60.................................600-650
MK 103....................................440.....................................800...............................141,000............................141.................................360-420

Yes some of the guns used different loads. There were an absolute crap load of 37mm guns from WW I and the 1930s, either take-offs of the early Maxim gun pom-poms for the early ones or experiential during the the 1930s. Many countries/companies were trying to stay in 1lb(454g) restriction for exploding shells used against people from the international treaties which faded away rather rapidly in the 1930s because 20mm and larger guns were intended to shoot at people but at airplanes and tanks. Just about all of them were either lower powered than the Japanese Ho-203 and weighed just about the same if not more, or for the higher powered weapons were getting into the US 37mm AA gun/German Flak 18 category. 160-300kg gun weight and rates of fire around 120-160. Things improved somewhat during WW II. Things changed a lot after the war.

There is an interesting chart in Anthony Williams book "Flying Guns of WW II" on the efficiency of aircraft guns where he figures out the "power" of a gun (shell weight, velocity, chemical content) times rate of fire and divides by gun weight. Does not include ammo weight. .303 Browning is 2.1 on scale. Only 3 guns are above 5 but not all are listed.
The Mk 108 is 9.7, the MK 103 is 4.9 as is MG 151. The other high scores are the Soviet B-20 at 6.8 and the Hispano MK V at 5.7. The US 37mm M4 is rated at 1.7.

The Soviet NS-37 is 2.5. The gun has the a rate of fire of 4rps, a power factor of 106 (most powerful on the chart for a gun power rating of 424 but the gun weight of 170kg kill it.
Now in this 'system' velocity plays an important part so it does not compare just explosive load so there is some room for interpretation. Both German 30mm guns have more "power" and their higher rates of fire and lower weights push them well over the top of the NS-37 (which many have been figured with too high an MV). At any rate MY figuring of the later N-37 is about 5.5.

From the Bf 109 standpoint, it is mostly about how much a power has the motor cannon, since going to gondola 20mm guns have had a bad impact on speed, RoC and maneuverability. The more powerful the motor cannon, the better.

The problem is hitting with a single gun, especially a slow firing one. Even a 420rpm gun is only going to fire 21 round in a 3 second burst.
One N-37 is 103 kg not including feeds, mount.
Two MG 151s is 82 kg
Three 151s is 126kg.
The 37mm gun has to equal the firepower of 2.5 to 3 MG 151s.
Replacing even a 60kg MK 108 with a 103-120kg 37mm is going to have a impact on speed (slight) climb (proportional to weight) and slight on maneuverability (weight distribution stays the same, increase in wing loading slight, depends on ammo supply).
Soviet 37 X 155 ammo is about 1.5kg per round. Granted a German 37mm can use lighter projectiles but the ammo is going to be heavier than MK 108 ammo.

At sea level, the 117g HE shell from a MG FFM needed 1.080 seconds to travel to the 1st 500m, the 92g M-shell needed 1.093. That is about 1% difference, or, in the words of late Paul Harrell, not enough of a difference to make a difference.

Those figures may be correct, the problem for long range shooting is that 500 meters seems to be the cross over point (or slightly shorter). Since the 117g shell started out at 585m/s and the 92g shell started at 700m/s the Mine shell has lost considerably more speed than the 117g shell and things are going to get worse, quickly.
There is chart in the Anthony Williams book "Flying Guns of WW II" for max combat ranges at 3000 meters and 6000 meters for assorted guns against bombers.

gun........................max R 3000m..................max R 6000m..............max effective.
Mg 131.....................700.....................................1000..............................400
MG 151.....................800.....................................1100..............................600
MG 151 117g.........750......................................1050......................................
MG 151 92G...........600.........................................800............................400
MK 108.....................900......................................1100............................400
MK 103...................1300.....................................1650............................800

The authors compiled this from several different sources. Without know how they judged things it is a bit iffy but it gives some ideas, Germans apparently did not consider the MK 108 quite as short ranged as some modern writers believe. On the other hand the standard 30mm MK 108 shell lost 47% of it's velocity at sea level and took 1.66 seconds to travel 600 meters. It was getting into the ping-pong ball part of it's trajectory even if longer than may believe. We can also refer back to RAF pilots opening fire in training at 3 times the ordered distance (900yds instead of 300yds) which plays hell with all sorts of things (convergence zones being a big one). I emphasis training as there was nobody shooting back at them and the target sleeves were not going to bomb anything. Performance in combat was NOT going to be better.
At least one German pilots BoB memoir claims he didn't fire a gun from a 109 until his leader had him fire his guns at waves in the English channel on the way to/from England. Standard of training increased/decreased in 1943?

 

[tomo pauk]

For WW II 37mm guns and the German 30mm at the end.
Gun........................................shell weight....................MV m/s...........................Joules....................gun weight/KG....................rate of fire
Japanese Ho-203.................475.....................................570................................77,200..............................89.......................................120
US M4......................................608.....................................610..............................113,000..............................96.................................140-150
US M10...................................608.....................................610..............................113,000........................... .109................................150-170 (belt feed)
Japanese Ho-204................475.....................................710...............................120,000............................130.....................................400
Soviet NS-37.........................735....................................810................................285,000.......................160-170............................240-260
Soviet N-37............................735....................................690................................175,000.............................103...............................400-430
MK 108.....................................330...................................505...................................42,100..............................60.................................600-650
MK 103....................................440.....................................800...............................141,000............................141.................................360-420

Thank you for the effort to type out and format stuff.
Ideally, IMO, the 'MK 103/37' should've been at about 150-160 kJ, ie. in-between the historical 103 and the N-37, and about 400 rd/min. Weight of ~140 kg is a bit of a problem, but not an excessive one (remove the cowl guns and the respective ammo to cancel the weight gain a bit, as it was planned for the MK 103-armed 109K version, that was also to be armed with a pair of MK 108s).

There is an interesting chart in Anthony Williams book "Flying Guns of WW II" on the efficiency of aircraft guns where he figures out the "power" of a gun (shell weight, velocity, chemical content) times rate of fire and divides by gun weight. Does not include ammo weight. .303 Browning is 2.1 on scale. Only 3 guns are above 5 but not all are listed.
The Mk 108 is 9.7, the MK 103 is 4.9 as is MG 151. The other high scores are the Soviet B-20 at 6.8 and the Hispano MK V at 5.7. The US 37mm M4 is rated at 1.7.

The Soviet NS-37 is 2.5. The gun has the a rate of fire of 4rps, a power factor of 106 (most powerful on the chart for a gun power rating of 424 but the gun weight of 170kg kill it.

Thank you again.
I think that we can agree that, despite the same score of 4.9, the MK 151(/20?) is/was a far worse bomber killer than the MK 103, let alone than a 37mm. Necessitating that aircraft must carry at least 3 of these (for the 109; 4 for the Fw 190), so any weight and drag saving is not there anymore.

The problem is hitting with a single gun, especially a slow firing one. Even a 420rpm gun is only going to fire 21 round in a 3 second burst.
One N-37 is 103 kg not including feeds, mount.
Two MG 151s is 82 kg
Three 151s is 126kg.
The 37mm gun has to equal the firepower of 2.5 to 3 MG 151s.
Replacing even a 60kg MK 108 with a 103-120kg 37mm is going to have a impact on speed (slight) climb (proportional to weight) and slight on maneuverability (weight distribution stays the same, increase in wing loading slight, depends on ammo supply).
Soviet 37 X 155 ammo is about 1.5kg per round. Granted a German 37mm can use lighter projectiles but the ammo is going to be heavier than MK 108 ammo.

I've already noted that the cowl MGs + ammo will need to go on the 109.
Germans were serious with introducing a 400+- rd/min MK 103 on their fighters for 1945, probably figuring out that the greater MV is a good trade-off for the lower RoF. A high RoF gun will not make a badly aimed shot to hit (it will land more hits if the aim was true, though), pilot still needs to do his job well.
The 37mm gun I was suggesting might've been a good ballistic match with the MG FFM, the cannon that was easy to install within the wings of the Bf 109. So there is one 37mm and two 20mm on a Bf 109.

Those figures may be correct, the problem for long range shooting is that 500 meters seems to be the cross over point (or slightly shorter). Since the 117g shell started out at 585m/s and the 92g shell started at 700m/s the Mine shell has lost considerably more speed than the 117g shell and things are going to get worse, quickly.

The shell is not trying to win a bar bet, but to reach the target and make damage. That it lost the airspeed on a greater rate, IMO, does not matter, what mattered is that it hit the target while using the same time as the heavier shell.

The authors compiled this from several different sources. Without know how they judged things it is a bit iffy but it gives some ideas, Germans apparently did not consider the MK 108 quite as short ranged as some modern writers believe. On the other hand the standard 30mm MK 108 shell lost 47% of it's velocity at sea level and took 1.66 seconds to travel 600 meters. It was getting into the ping-pong ball part of it's trajectory even if longer than may believe.

Author Fritz Hahn in his book "Deutsche Geheimwaffen 1939 - 1945. Flugzeugbewaffnungen" says that in theory, for the MK 103, it will require 40 shells fired from 500m to kill a 4-engined bomber with 50% 'guarantee', and with 76 shells fired to do it at 95% 'guarantee'. For the MK 108, it was 48 and 88.
At 1000m, it was 104 (50%) or 203 (95%) for the 103, and 120 (50%) for the 108.
Obviously, the 103 has no edge over the 108 wrt. the lethality of a single shell, unlike what the 37mm should have. Author notes that just 4 30mm shells are required, vs. many sources saying 5 shells for a 4-mot - one just loves when the sources do not agree with each other.

He says that, at 500m, no altitude listed, the MK 103 shell will drop by 1.6m, vs. the 108 shell drop of 6m.

One of the problems Germans had with the MK 108 seems to be it's susceptibility for the off-angle vs. the target to spoil the chance to hit. For the MK 103, the 30 deg angle reduced the chance to kit by a factor of 5 vs. a 0 deg attack, while for the MK 108 the chance to hit was reduced by the factor of 12 (twelve). Even the 15 deg shot redcued the hit % by factor of ~5(!) on the 108, vs. the factor of 2 for the 103. That is both for 400 and 800m shooting distances.

Granted, a 700+- m/s 37mm shell will not have the ballistics of the 860 m/s 30mm shell, but it will still outpace handily the MK 108, and will make it's hits count for more.

We can also refer back to RAF pilots opening fire in training at 3 times the ordered distance (900yds instead of 300yds) which plays hell with all sorts of things (convergence zones being a big one). I emphasis training as there was nobody shooting back at them and the target sleeves were not going to bomb anything. Performance in combat was NOT going to be better.
At least one German pilots BoB memoir claims he didn't fire a gun from a 109 until his leader had him fire his guns at waves in the English channel on the way to/from England. Standard of training increased/decreased in 1943?

German pilot training was going ever lower IIRC.
Ideally, what LW needed is a weapon of good/great ballistics and punch, a well-trained pilot, and a computing sight. What the LW had in 1943-45 were the guns with shortcomings (30 mm types either not able to fit well on 109 & 190, or with low MV; 20mm cannons felt as lacking against the 4-mots), pilot training standard going ever lower, and the run-on-the-mill gunsight (EZ-42 notwithstanding, coming in in penny packets).

 

[tomo pauk]

There is a book, in German language, that deals with the German synthetic fuel program. named "Der sythetische Treibstoff" by W.Birkenfeld. At a steep price tag, better than 350 US$!
Several tables from the book are posted in this forum. One of them shows that Leuna facility was not just making the avgas, but also the 'normal' gas (under 80 oct), propane/butane as well as diesel. Jump in production of diesel is to be noted - from about 13% of total production in 1940, to 40% in 1941-43 (in absolute, about 4 times as much). In the same time, total production of gasoline (avgas + 'normal') went from ~350K tons in 1937 & 38 down to 250-270K tons in 1942-44 (with ever-increasing % of avgas).

Some questions:
- any takers on how easy/hard was to get the diesel fuel in a syn fuel plant?
- why such a dip in the total gasoline production of the Leuna facility between 1938 and 1941 - the 'extra step' to get to 87+oct cost?