Why wasn't the German 75mm KwK 40 simply copied and manufactured for Allied armor?

[On the way]

Arguably the best tank gun of WW2, and far superior in performance to the M4 Sherman 75mm short barrel and the Russian T-34 76mm and 85mm tank guns. And able to penetrate the frontal armor of their own Tigers and Panthers and Panzer IVs with AP. They must have captured examples of these guns in North Africa, and know how much better this gun is to anything in their inventory. How hard would it be to reverse engineer it? The M4 Sherman turret has shown ability to be upgunned. The French CN75 75mm gun from the AMX-13 was installed into the M4 by the IDF, so it should take the KwK40. I am sure the same thing could be done with the T-34. If they can go from a 76mm to an 85mm, they should be able to fit the KwK40. From what I understand, even the M4E8 76mm M1 having similar AP abilities to the KwK40, but inferior HE ability to the German gun, still making the German gun superior. And the part about logistics is a non starter. The supply chain set up for 75mm ammo is still the same chain you use for 75mm ammo for the German guns. And you give all Shermans in the field the ability to fight enemy tanks effectively versus having to wait for a tank destroyer to show up to kill a Panther, Tiger, or something else.  

[sunday]

1 hour ago, On the way said:

From what I understand, even the M4E8 76mm M1 having similar AP abilities to the KwK40, but inferior HE ability to the German gun, still making the German gun superior. And the part about logistics is a non starter. The supply chain set up for 75mm ammo is still the same chain you use for 75mm ammo for the German guns. And you give all Shermans in the field the ability to fight enemy tanks effectively versus having to wait for a tank destroyer to show up to kill a Panther, Tiger, or something else.  

It looks like the 76mm was good enough to do that job, without waiting for 90mm-gunned tank destroyers.

[RichTO90]

Because the American 76mm Gun M1, the British Ordnance QF 17-pounder, and the Soviet 85mm were just as good guns, all developed and ready for production by the time the first 7,5cm Pak 40 was captured. The Pak 40 cannon tube, breech, and recoil mechanism were lighter because the Germans accepted somewhat more risk in gun designs, but otherwise they were not much different and the 76mm was probably the most accurate of all.

It was not the guns that made the difference in penetration, it was the projectiles. There, at least with the Americans, you have a legitimate question.

The problem with the HE in the British 17-pounder was the design of the cartridge case and the amount of propellant used, which resulted in a slightly higher muzzle velocity and a flatter trajectory than was desired for a high-explosive round. The complaint with the American HE round is that it was not as effective as the 75mm M48 High Explosive round as used in the 75mm Gun M2 and M3, not that it was not as effective as the German round.

Edited September 28 by RichTO90

[RichTO90]

BTW, the bursting charge of the German 75mm HE was 1.41 pounds of Amatol, while that of the 75mm M48 was 1.47 pounds of TNT and the 76mm M42 was 0.86 pounds of TNT (U.S. Army Ordnance was concerned with the stability of Amatol, so preferred TNT as an explosive filler). So the German round was roughly equivalent to 1.55 pounds of TNT, making it about the same as the M48, but superior to the M42, not that American tankers complained that it was not as effective as the German 75mm HE round, they complained that it was not as effective as the American 75mm HE round. 😁 A slight, but important difference.

[old_goat]

2 hours ago, RichTO90 said:

It was not the guns that made the difference in penetration, it was the projectiles.

Exactly. Soviet 85mm gun was quite good, but fired shitty projectiles, thats why it couldnt achieve higher penetration than german 75 L/48. Soviets were always behind in terms of ammo development. Post war, with new ammo, the same 85mm gun had actually better penetration than the Panther's long 75! (obviously, it was waaaay too late)

[urbanoid]

2 hours ago, old_goat said:

Exactly. Soviet 85mm gun was quite good, but fired shitty projectiles, thats why it couldnt achieve higher penetration than german 75 L/48. Soviets were always behind in terms of ammo development. Post war, with new ammo, the same 85mm gun had actually better penetration than the Panther's long 75! (obviously, it was waaaay too late)

Well, not necessarily, in theory they could be fighting against the French Panthers.  

[PaulFormerlyinSaudi]

Why weren't German machine guns copied by the Allies? Why wasn't the very simple bazooka copied by the Germans and Soviets? Copying a gun is a rather big deal. Every Ordnance department in the world looked at foreign designs but in (almost?) every case thought that it was easier to continue with patterns already in the pipeline that to scrap it all and start again. 

 

(Are there examples of someone back engineering a major weapon system? Perhaps the American development of their version of the butterfly bomb.)  

[RichTO90]

1 hour ago, PaulFormerlyinSaudi said:

Why weren't German machine guns copied by the Allies?

U.S. Army Ordnance did attempt to copy the MG 42. It failed, for numerous reasons, not least of which they had a limited time frame to do so that would have resulted in any such copies getting into the hands of troops trained to use them. It also highlighted how problematic copying from metric to imperial and vice versa was. Notably, when the U.S. Army did finally develop "its" similar gun, the M60, it replaced the "heavy" M1917 and "light" M1919 machine guns in the Rifle Battalion, it was not deployed as a "squad automatic weapon" in the same manner as the MG 42. Instead, they first tried to make the M14 the SAW, replacing the BAR, then tried to give every rifleman and automatic weapon in the M16, then finally adopted another foreign weapon, the M249 (FN Minimi) as a SAW...in 1984 (who said Orwell wasn't prescient?) Now they are looking for a new one, which will probably be in service in another twenty years or so.

Quote

Why wasn't the very simple bazooka copied by the Germans and Soviets? Copying a gun is a rather big deal. Every Ordnance department in the world looked at foreign designs but in (almost?) every case thought that it was easier to continue with patterns already in the pipeline that to scrap it all and start again.

Copying stiff like this is not like copying with a Xerox. 😁 The Bazooka was not copied by the Germans because they already were experimenting with various light man-portable antitank weapons. The Bazooka simply showed they did not need wheels on it. The Soviets developed their version too late and relied on hand-thrown types because their industry was already at capacity.

 

Quote

(Are there examples of someone back engineering a major weapon system? Perhaps the American development of their version of the butterfly bomb.)

I would have to look into it more.

Edited September 29 by RichTO90

[Rick]

On 9/28/2024 at 11:38 AM, RichTO90 said:

Because the American 76mm Gun M1, the British Ordnance QF 17-pounder, and the Soviet 85mm were just as good guns, all developed and ready for production by the time the first 7,5cm Pak 40 was captured. The Pak 40 cannon tube, breech, and recoil mechanism were lighter because the Germans accepted somewhat more risk in gun designs, but otherwise they were not much different and the 76mm was probably the most accurate of all.

It was not the guns that made the difference in penetration, it was the projectiles. There, at least with the Americans, you have a legitimate question.

The problem with the HE in the British 17-pounder was the design of the cartridge case and the amount of propellant used, which resulted in a slightly higher muzzle velocity and a flatter trajectory than was desired for a high-explosive round. The complaint with the American HE round is that it was not as effective as the 75mm M48 High Explosive round as used in the 75mm Gun M2 and M3, not that it was not as effective as the German round.

Could the U.S. Navy 3" ammunition be fired from the U.S. Army 76mm gun? Wondering if so, would the U.S.N. a.p. round be better than the Army one?

http://www.navweaps.com/Weapons/WNUS_3-50_mk10-22.php

[bojan]

4 hours ago, RichTO90 said:

U.S. Army Ordnance did attempt to copy the MG 42. It failed, for numerous reasons...

Yugoslavia acquired production documentation for MG42 (and few other things) from Czechoslovakia in 1947. It took until 1954 to put gun into service. Part of that time was due the need to practically fully rebuild Zastava factory (due the Germans looting it in 1945 it had less than 5% of the machines it had in 1941). But there were other major issues:

Documentation was incomplete. In particular hardness requirements for some parts (firing pins in particular) and some tolerances were missing. To solve this 500 existing MG42s were withdrawn from troops and disassembled, and then hardness tested and dimensions painstakingly taken from parts in order to know at least what is an average tolerance on some parts. This took quite a bit, since hardness of parts was not uniform in all guns (IOW, German own QC was sloppy). In the end it was found out that, contrary to usual practice, firing pins have to be either relatively soft of hard - medium hardness ones just did not work. Soft ones ofc deformed after some time, but at least worked. Hard ones worked best, but they broke, damaged timing adjustment rings and in some cases rollers (if rollers were not super hard as they were supposed to be, but other, due the Germany slipping QC were not). All this took a lot of trials and error.

Then there was a problem of stamping receivers. There was no original presses, but new presses, acquired in the US were set up in 1952. This did not work, because presses controls were in the imperial system, and while there was in theory no problem with using those to make metric parts it turned out that MG42 receiver required very, very exact pressures, press travel length and press time to form properly. This was ofc all in metric, so doing it on imperial presses was quite a PITA, and receivers started cracking. This was reduced by reducing hardness of receivers, but then they started bending. This was never fully solved, until it was discovered, by extensive testing of German made MG42s that this was issue with good deal of those guns also, again due the German WW2 QC being not best.

Another year later this was finally solved and guns started rolling off the production line. But in practice they had problems with bolts breaking. Why? Because  part of the documentation acquired from Czechoslovakia was actually not original, but from their own (aborted) attempt to produce MG42 sometimes in 1945-46. So they decided that forged and then painstakingly ground bolts were too slow to produce, so they switched process to casting, machining and then case hardening bolts. This ofc did not really work, so again things had to be adjusted.

Looking at all this, while knowing that US had next to zero production documentation when they attempted to do a copy - there is absolutely no surprise that endeavor failed.

 

*But wait, what did Germans do, how it came their guns worked better and they did not have issues? 

Well, that was not exactly true - just as with "3000 rounds and into junkpile" StG-44s, they just accepted that guns will be burned out faster and decided to concentrate on producing more guns, not even bothering with majority of spare parts, since guns were lost so quickly that whole replacement firing pins and bolts or receivers cracking** and bending did not show as a problem in practice. It took a peacetime production and peacetime army to actually notice those problems. For the same reason, when MG-3 was introduced  in the Bundeswehr - Germans also had to go through same painful process of fixing "errors" that were totally acceptable during WW2 but were totally unacceptable for any peacetime army.

**Swiss, for their M51 MG went with machined receiver to solve cracking and bending. They also changed locking from rollers to flappers (in order to solve bolt bounce another nasty problem with original MG42, solved on MG3 by reducing cadence and angles of locking surfaces), which made their M51 practically new gun.

 

[bojan]

6 hours ago, PaulFormerlyinSaudi said:

...Why wasn't the very simple bazooka copied by the Germans and Soviets? ...

Soviets studied Bazooka and decided that it was not worth a copy for a multitude of reasons. They decided to concentrate on recoiless weapons (vs rocket propelled), as that was seen as a better way to get infantry AT weapons. First prototypes were ready for production (more-less) by mid 1944, but since Red Army was generally moving forward, production of such defensive weapons was not considered a priority, so it was postponed until after the war when some issues plaguing existing weapons could could be solved. SPG-82 recoilless gun (which was ready for production in 1944...) and RPG-2 handheld recoilless launchers were introduced in the second half of the '40s as a result of that.

[txtree99]

The Germans did copy the bazooka 

 

In late 1942, numbers of early-production American M1 Bazookas were captured by German troops from Red Army forces who had been given quantities of the Bazooka under lend-lease. There were also examples captured during the Operation Torch invasions in the North African Campaign.[9] The Germans promptly developed their own version of the weapon called the Panzerschreck, increasing the diameter of the warhead from 60 mm to 88 mm (2.4 to 3.5 in), which as a result, gave it significantly greater armor penetration. During U.S. trials of the M1, calls for a larger-diameter warhead had also been raised by some ordnance officers but were rejected. Later in the war, after participating in an armor penetration test involving a German Panther tank using both the Raketenpanzerbüchse, or RPzB 54 Panzerschreck and the U.S. M9 Bazooka, Corporal Donald E. Lewis of the U.S. Army informed his superiors that the Panzerschreck was "far superior to the American Bazooka": 'I was so favorably impressed [by the Panzerschreck] I was ready to take after the Krauts with their own weapon.'[45]

 

https://en.wikipedia.org/wiki/Bazooka

 

[Interlinked]

On the Soviet side of things, the 85mm borrowed the cartridge and internal ballistics from an existing 85mm anti-aircraft gun, so designing the gun was easy and supplying it was economical. The gun itself was made very compact and narrow. That was a critical factor in Soviet tanks being able to fit larger caliber guns in smaller turret rings. 

The Yugo trials that Bojan (?) shared many years ago showed that the 85mm's AP could defeat the upper glacis and turret front of an M4A3E4 Sherman at the same range as 75mm 40's AP. So 85mm isn't worse in terms of pure capability on flat to well-sloped targets, and it would conceivably outperform 75mm AP on thinner, more heavily sloped plates, like maybe the side armour of a Pz. IV or a Panther at an angle. That's before counting other factors like an 85mm shell delivering much more momentum into the target, probably increasing the odds of jamming a turret ring on a non-penetrating hit on the turret. And of course, complete penetration by a larger shell like the 85mm wouldn't produce the same behind-armour effect as a complete penetration by a 75mm shell. 

Edited September 30 by Interlinked

[RichTO90]

5 hours ago, Rick said:

Could the U.S. Navy 3" ammunition be fired from the U.S. Army 76mm gun? Wondering if so, would the U.S.N. a.p. round be better than the Army one?

http://www.navweaps.com/Weapons/WNUS_3-50_mk10-22.php

The projectiles could, but I doubt the cartridges were interchangeable? The Army "3-inch" actually used three different cartridge cases. The 3-inch M1917, M1925M1, M2, and M4 AA guns and the M1903 Coast Artillery gun all used a larger cartridge, while the 3-inch M1918, M1, and M3 AA guns, the M1902 Coast Artillery gun, the M5 and M7 Antitank, and the M6 Tank guns all used a smaller cartridge case. There were also two sizes of Navy cartridges for their various 3-inch guns.

And yes, the Navy 3-inch AP Mark 29 projectile performed markedly better than the Army M62 and M79 AP projectiles in comparative tests done just postwar at Dahlgren, as I mention in American Thunder. The Army designs consisted suffered from shatter and deforming at similar velocities and angles of impact that left the Navy projectiles intact. Perforation both by Army and Navy standards was also much better for the Navy round. The results were damning both for the Army Ordnance designs and manufacturing specifications, but also for the simple failure to cooperate by the two Ordnance establishments.

On top of that, the Army Ordnance knew by hearsay as well as from test results at Aberdeen as early as late 1942/early 1943 that the German AP projectile designs and specifications, as well as the German fuze designs, were far superior still, but took no action to improve the American designs.

[RichTO90]

3 hours ago, txtree99 said:

The Germans did copy the bazooka 

In late 1942, numbers of early-production American M1 Bazookas were captured by German troops from Red Army forces who had been given quantities of the Bazooka under lend-lease. There were also examples captured during the Operation Torch invasions in the North African Campaign.[9] The Germans promptly developed their own version of the weapon called the Panzerschreck, increasing the diameter of the warhead from 60 mm to 88 mm (2.4 to 3.5 in), which as a result, gave it significantly greater armor penetration. During U.S. trials of the M1, calls for a larger-diameter warhead had also been raised by some ordnance officers but were rejected. Later in the war, after participating in an armor penetration test involving a German Panther tank using both the Raketenpanzerbüchse, or RPzB 54 Panzerschreck and the U.S. M9 Bazooka, Corporal Donald E. Lewis of the U.S. Army informed his superiors that the Panzerschreck was "far superior to the American Bazooka": 'I was so favorably impressed [by the Panzerschreck] I was ready to take after the Krauts with their own weapon.'[45]

 

Sorry, but no, that is an urban myth. Production of the 2.36" Rocket Launcher only began in June 1942 and first issue was to units in Operation Torch , which sailed in October 1942. Only 3,000 launchers and 8,500 rockets were shipped under Lend-Lease to the Soviet Union. AFAICT they were probably shipped to the Soviets under the III or IV Protocol, so after 1 July 1943. The Soviets never issued the Bazooka that I can find but retained them for testing and technical evaluation, which was overall negative.

The Germans began development of the Faustpatrone/Panzerfaust in the summer of 1942, the 8.8cm  Ofenrohr/Panzerbüchse 43 in January 1943, and the Puppchen AKA 8.8cm Raketenwerfer 43 in the summer 1943. How much captured examples of the Bazooka led to the Ofenrohr is hard to say, given the Faustpatrone was already in development. 

[Stuart Galbraith]

I found an amusing item the other day, where was supplied the PIAT in 1942, and the Soviets very firmly told us they didnt want anymore!

 Although they were still using PTRD rifles at least as late as Kursk, and a PIAT at the very least, was considerably better than an antitank grenade.

[JWB]

 

I always liked this system because of simplicity.

[Markus Becker]

16 hours ago, bojan said:

Yugoslavia acquired production documentation for MG42 (and few other things) from Czechoslovakia in 1947. It took until 1954 to put gun into service. Part of that time was due the need to practically fully rebuild Zastava factory (due the Germans looting it in 1945 it had less than 5% of the machines it had in 1941). But there were other major issues:

Documentation was incomplete. In particular hardness requirements for some parts (firing pins in particular) and some tolerances were missing. To solve this 500 existing MG42s were withdrawn from troops and disassembled, and then hardness tested and dimensions painstakingly taken from parts in order to know at least what is an average tolerance on some parts. This took quite a bit, since hardness of parts was not uniform in all guns (IOW, German own QC was sloppy). In the end it was found out that, contrary to usual practice, firing pins have to be either relatively soft of hard - medium hardness ones just did not work. Soft ones ofc deformed after some time, but at least worked. Hard ones worked best, but they broke, damaged timing adjustment rings and in some cases rollers (if rollers were not super hard as they were supposed to be, but other, due the Germany slipping QC were not). All this took a lot of trials and error.

Then there was a problem of stamping receivers. There was no original presses, but new presses, acquired in the US were set up in 1952. This did not work, because presses controls were in the imperial system, and while there was in theory no problem with using those to make metric parts it turned out that MG42 receiver required very, very exact pressures, press travel length and press time to form properly. This was ofc all in metric, so doing it on imperial presses was quite a PITA, and receivers started cracking. This was reduced by reducing hardness of receivers, but then they started bending. This was never fully solved, until it was discovered, by extensive testing of German made MG42s that this was issue with good deal of those guns also, again due the German WW2 QC being not best.

Another year later this was finally solved and guns started rolling off the production line. But in practice they had problems with bolts breaking. Why? Because  part of the documentation acquired from Czechoslovakia was actually not original, but from their own (aborted) attempt to produce MG42 sometimes in 1945-46. So they decided that forged and then painstakingly ground bolts were too slow to produce, so they switched process to casting, machining and then case hardening bolts. This ofc did not really work, so again things had to be adjusted.

Looking at all this, while knowing that US had next to zero production documentation when they attempted to do a copy - there is absolutely no surprise that endeavor failed.

 

*But wait, what did Germans do, how it came their guns worked better and they did not have issues? 

Well, that was not exactly true - just as with "3000 rounds and into junkpile" StG-44s, they just accepted that guns will be burned out faster and decided to concentrate on producing more guns, not even bothering with majority of spare parts, since guns were lost so quickly that whole replacement firing pins and bolts or receivers cracking** and bending did not show as a problem in practice. It took a peacetime production and peacetime army to actually notice those problems. For the same reason, when MG-3 was introduced  in the Bundeswehr - Germans also had to go through same painful process of fixing "errors" that were totally acceptable during WW2 but were totally unacceptable for any peacetime army.

**Swiss, for their M51 MG went with machined receiver to solve cracking and bending. They also changed locking from rollers to flappers (in order to solve bolt bounce another nasty problem with original MG42, solved on MG3 by reducing cadence and angles of locking surfaces), which made their M51 practically new gun.

 

👏🏻👏🏻

[Yama]

After the war, Finnish Army considered replacing 85mm guns from T-34's with 75mm KwK 40, due to latters better armour penetration.

Also IIRC, when Charioteer was acquired, there was a proposal to use 20pdr gun in either T-34 or StuG.