RE: German 75mmL43, L48 and L46 velocities (Full Version)

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Mobius -> RE: German 75mmL43, L48 and L46 velocities (10/25/2015 2:45:00 PM)

This chart doesn't seem to be used to show what is reported in the datenblatt either. I've been trying to match the actual velocity at a range to the penetration reported and they aren't the same.
So the daten has the 75/L70 penetration as 138mm at 100m. The velocity of a V0=925m/s shell will be about 912m/s at 100m. That is 141mm from the chart.
The daten has the 75/L48 penetration is 82mm at 1000m. Also, German documents say the the impact velocity is 637m/s at 1000m for this shell. Which is 79mm from the chart.
I don't know what is going on with the differences. Maybe the Germans are normalizing the data for a constant armor quality like the US did.

[image]local://upfiles/21308/8EB0B0EFE6754EAB874292F5D8DB8074.jpg[/image]



Mobius -> RE: German 75mmL43, L48 and L46 velocities (10/26/2015 12:10:46 AM)

Here's a great find. Looks like a US chart that combines the ballistics of several 75mm German guns.
In fact it matches the Aberdeen data tables in the Hoffschmidt book. (I think, I only checked a few data points.)


[image]local://upfiles/21308/698C7F8A9BF8455BB31FE921123E7C69.jpg[/image]



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/26/2015 10:01:28 PM)

I suspect they used the wrong KWK 40 velocity. Instead of 2300 Fps, it might be 2500 Fps.

It is interesting that they are using all 3 weapons based on the 7,5 cm PzGr 39. The only real difference is velocity and two driving bands on the Panther projectile.

The German graph is using 2 variables, that is velocity and hardness. The test plates were different hardness depending on thickness. This accounts for the non-linear nature of the curves.



Mobius -> RE: German 75mmL43, L48 and L46 velocities (10/27/2015 1:58:55 AM)

Here's a better one:
The first one I posted (1944) was throwing all my ballistics off. It was correct down to around 2600 f/s then started to lose penetration and velocity too fast. It didn't match my Aberdeen data for the Pak 40 very well.

I found these on either a War Thunder or World of Tanks forum. There's another one from 1943 and has single gun of MV of 2400f/s so isn't much use.
[image]local://upfiles/21308/2284289258544E86922BC0967C14442E.jpg[/image]
This second one was produced in 1945.
Still they got the MV of the 75mm/L70 wrong as well as a the StuG 40.
I hope there is a chart from 1946 out there that corrects this.

Elron, your first post you asked if there are any orginal sources to the data. The answer is that there are a number. Not that many are very good.






Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/27/2015 11:46:38 AM)

I asked what the "Ample Evidence" was. I have not seen much. And, if we look at these last couple of graphs, I really doubt many non-German information at this point.



Mobius -> RE: German 75mmL43, L48 and L46 velocities (10/27/2015 2:35:08 PM)

The last graph may be the source of the PaK 40 2600 f/s Aberdeen table. It matches pretty close, as far as I can read a line width and +/- 1mm. The line at the bottom with the tics at different ranges is pretty close, but not an exact match, to the German ballistics for 790m/s gun.

[Edit] It occured to me why the ballastics are not an exact match. The German velocity data is in m/s and the US is in ft/s. The German data could round off as much a 2 ft/s in either direction.



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/28/2015 3:05:30 PM)

Do you know what document they are from?

Aberdeen tested the Panther tank in 1946. They tested accuracy and I would assume penetration according to US standards. The Soviets 'tested' the initial Panthers captured at Kursk. This includes shooting one with a 8,8 cm L71 weapon and shooting a Elephant with the Panther gun (including using the rare AP 40 round). The Panther AP40 was not the same as a KWK 40 or Pak 40 BTW, it used the larger Pak 41 bolt inside.

I don't think I have seen much in the way of British testing. They must have tested especially after capturing weapons after Normandy. They certainly did reports on Africa battle weapons.

I think you are assuming data and should identify the source beyond "World of Tanks" posts.



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/28/2015 3:21:13 PM)

Here is a T34 that has been subjected to test shots from a Tiger 8,8 cm KWK 36. The range is stated as 1500 meters. There seems to be clear penetrations on the lower hull and joint between the lower and upper hull, but the one 'perforation' next to the removed driver's hatch, I have my doubts. This is possibly a ricochet that had enough energy to crack the impacted area and drive armor inward.



[image]local://upfiles/52248/732746ABE4A74E3BABD7E449B2AEA3DD.jpg[/image]



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/28/2015 3:26:26 PM)

Here is a Panther that has been hit by an 'Elephant' gun. I am not sure of the range. It is stated as being a ricochet. The effects inside are devastating. A cone shaped area of armor is missing through the plate. This is an early (Kursk) Panther D and may have face hardened armor.



[image]local://upfiles/52248/8FCFACCF71B446EBBB93FF2889C5B8A8.jpg[/image]



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/28/2015 3:39:26 PM)

So, my thought is that the Germans are just too rigid in understanding armor defeating weapons. Reports claim the T34 are "hard to burn" from the front aspect. Basically, it is hard to get the Pz Gr to get inside and explode. But, many weapons that have a T/D advantage could make soft kills by killing/maiming the driver, etc. So, a better way of expressing penetration on highly sloped armor is really just a percentage. Having a specification like 50% chance of penetration, and 50% perforation (any) is more realistic of expected effects. Again, it is too expensive to test this with real sloped armor, one must just do an initial investigation on what velocity that is and verify using 60 degree armor.

If a KWK 36 could make that damage at 1500 meters, I would be assured that a Pak 40 could also do that damage in the 1000 type range. I believe the 'Yugo' tests had just a "perforation" type 'spec'.

The Soviet hard armor may have actually made the T34 more vulnerable. Hardness is good to a point, then it leads adiabatic shear problems and failure at higher levels.



Mobius -> RE: German 75mmL43, L48 and L46 velocities (10/28/2015 7:58:13 PM)

quote:

ORIGINAL: Elron Hubbub
If a KWK 36 could make that damage at 1500 meters, I would be assured that a Pak 40 could also do that damage in the 1000 type range. I believe the 'Yugo' tests had just a "perforation" type 'spec'.
They are no different than the US with a 50% penetration level.



Mobius -> RE: German 75mmL43, L48 and L46 velocities (10/28/2015 8:53:00 PM)

I've been trying to find another German source for 75mm/L70 velocity data. I have two sources both are in Spielberger's Panther book. But they don't agree with each other. One is a graph. I overlayed it on what the US ballistic formula outputs.

Also, is an output of the 75mm/L48 using the same US ballistics formula. It matches within +/- 2m/s out to 2500m of the German tabular data of the 75mm/L48. So the US formula works for the KwK40. Just not sure why it isn't matching the 75mm/L70 data that I have.

[image]local://upfiles/21308/AC4EA78DABBE4200B47859293252218B.jpg[/image]



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/29/2015 2:32:34 AM)

The large white circle on the T34 hull is from a 8,8 cm HE round. Supposedly tearing off the driver's hatch. The 8,8 cm HE was actually very high velocity and was used as a antitank weapon under certain conditions. Notably attacking side armor.



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (10/30/2015 12:14:04 PM)


quote:

ORIGINAL: Mobius

I've been trying to find another German source for 75mm/L70 velocity data. I have two sources both are in Spielberger's Panther book. But they don't agree with each other. One is a graph. I overlayed it on what the US ballistic formula outputs.

Also, is an output of the 75mm/L48 using the same US ballistics formula. It matches within +/- 2m/s out to 2500m of the German tabular data of the 75mm/L48. So the US formula works for the KwK40. Just not sure why it isn't matching the 75mm/L70 data that I have.

[image]local://upfiles/21308/AC4EA78DABBE4200B47859293252218B.jpg[/image]


Yes, something is obviously wrong. Or, both curves can't be correct. Since the projectiles are virtually the same, the flight characteristics should closely match. One should be able to just 'slide' the characteristic curve for the L48 over to the 'Panther' curve at 750 M/s and they should be very similar.

The Germans would say so also. They tested by varying velocity.

This brings up the point of how they did test and record velocity. I imagine the method used magnetized projectiles that are shot through coils at a very precise distance from each other. The coils are monitored through a oscilloscope that can capture each voltage produced as the projectile passes through. It can then deduce the time and therefore the velocity. I am not sure how they actually did it in WWII but that is a common scheme. Did anyone do it for multiple points along the firing arc? That would be the only way to really determine a characteristic curve like you are showing.



Mobius -> RE: German 75mmL43, L48 and L46 velocities (10/31/2015 3:23:21 PM)

That's right. They test the guns by firing at a set range of 50 or 100 meters or yards but vary the charges to simulate different ranges. But if they don't have the ballistics of the shells right then they aren't really testing the penetrations at those ranges. Chronographs seem to have been developed during the war so the accuracy should have improved toward the end. Because of dispersion they couldn't place them very far away from the gun.

Shells of a particular type should have about the same ballistics fired from different guns. One thing to note is that when the US 76mm went to a higher twist the ballistics improved a bit. If the shell spun at a higher rate it didn't lose velocity quite as fast.
http://www.panzer-war.com/Images/M9190776.jpg

My ballistics formula is a short version of the US formula but is not as involved as the highly detailed 6 degrees of freedom used by the military.



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (11/1/2015 2:33:19 PM)

So, the Americans tested the velocity of the 76mm weapons out to 7000 yeards?



Mobius -> RE: German 75mmL43, L48 and L46 velocities (11/2/2015 3:39:51 AM)

Or, they worked out the ballistics to that range.



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (11/2/2015 3:12:45 PM)

So they measured to 5000 yards? They list a penetration value for that range?



Mobius -> RE: German 75mmL43, L48 and L46 velocities (11/2/2015 7:14:44 PM)

It's all there.
The way those graphs work is you draw a line up from your range value (along the bottom) until it intersects the velocity curve. Then draw line right angle from that point until it intersects the armor angle curve of your choice. Then draw line straight down from that point until it intersects bottom values and read inches of penetration.

[image]local://upfiles/21308/5B2271AD2C1C4141B79456CD01D5378B.jpg[/image]



Mobius -> RE: German 75mmL43, L48 and L46 velocities (11/4/2015 1:44:21 PM)

This is a clue on how the US came up with their ballistic tables. They fired at 1500yds and measured the time it took to hit it. Then worked out what kind drag number the shell must have to achieve that.


[image]local://upfiles/21308/0D12340A683248409D1733089A5A5FE9.jpg[/image]



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (11/4/2015 2:38:48 PM)


quote:

ORIGINAL: Mobius

It's all there.



The dashed lines meaning some form of interpretation?



Mobius -> RE: German 75mmL43, L48 and L46 velocities (11/5/2015 1:03:30 AM)


quote:

ORIGINAL: Elron Hubbub
The dashed lines meaning some form of interpretation?


Just happen to run across this.
quote:

It will be noted that certain portions of the penetration curve are shown as broken lines. This represents an estimated performance for which actual firing data have not been obtained. The penetration curves are compiled for intact or shattered projectile, with the greater portion of the fragments, completely penetrating the plate.



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (7/16/2016 4:04:57 AM)

Been awhile.... In any case, I have a document that uses actual type-set print for April 1944...

Lots of good info in it. The numbers above the Pak 40 info are for the 7,5 cm L24 weapons from the previous page. The Pak 40 shows just the PzGr 39 as 2.73Kg of propellant. The KWK 40 shows 2.54 Kg of propellant. Many ammo types like HE and HEAT and Nb (smoke) show alternative propellant types to get the same velocity. This does not show for the German armor piercing ammo PzGr 39 or PzGr 40 for these 7,5 cm weapons. The document is concerned with explosives and propellants used in April 1944 in weapons that the German military is still fielding in some form.

It would seem that Hl/C (Heat) was common for most weapons at this time and they are listed separate from hl/B rounds.

I challenge anyone to produce any German document that shows that the Germans reduced the Pak 40 propellant as it must be in the case of a reduced velocity. In fact, if they did, then almost every type of ammunition would be using a cartridge that is too long. That is, there is no point to having a breech and cartridge that does not fulfill its potential in some ammunition used in it.

[image]local://upfiles/52248/7B7270903FC4444BAF3D37EAD0F45747.jpg[/image]



Mobius -> RE: German 75mmL43, L48 and L46 velocities (7/19/2016 10:44:03 PM)

This is worth posting.
Though the 1500m value of the Pak 40 pzgr39 is probably an error.


[image]local://upfiles/21308/F1B248B0EE0C48F5860F4438ECAB7269.jpg[/image]



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (7/19/2016 11:38:05 PM)

I believe its been posted in this thread before? Maybe a review would be worth it since its been awhile.

It looks to be from December 1942? It is very interesting for a number of things. The last column, if I read it correctly, says that Hl/B was the most used ammo in Dez. 42?????? WAY TO GO Hl/B!!!!!

I have been thinking lately about just what exactly is meant by the German use of the specification "lange" (ex: L46). I think they mean the barrel length from the muzzle (discount the muzzle brake) to the actual point in the tube that the rifling begins. Some claim that there are different methods, i.e. that you measure from the muzzle to the very rear of the breech. This would make the Pak 40 a very 'short' gun because it had such a long case. Something to research.

As a quick example, in the case of the Pak 40, in the second column above, there is a length stated as 3700mm. If we divide 3700 mm by 75mm we get 49.33 as a number. So, if we subtract 49.33-46=3.33*75mm=250mm. This is about the length that a projectile protrudes into the barrel and the driving band is. In other words, L46 means 75mm*46=3450 and that is the travel or distance that the projectile is under pressure. If you look at the note for '+' it mentions Bodenstuck. I take that to mean that the rifling and driving band meet.

i am not sure all nationalities did it like this.



Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (7/20/2016 1:06:46 AM)

tatsachliche lang +mm must mean what I describe...indeed length +mm



Mobius -> RE: German 75mmL43, L48 and L46 velocities (7/20/2016 1:55:23 PM)


quote:

ORIGINAL: Elron Hubbub
It looks to be from December 1942? It is very interesting for a number of things. The last column, if I read it correctly, says that Hl/B was the most used ammo in Dez. 42?????? WAY TO GO Hl/B!!!!!
I don't know all the load outs for PaK and KwK 75mm guns so some may not have HEAT for certain time periods. Right now there can only be one type of HEAT shell from each gun. So early war guns have the penetration of the HL/B and later models that of the improved HL/C.




Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (7/20/2016 4:45:36 PM)

Hl/C is listed for most all weapons in April 1944. I would suppose that it was actually available a little earlier than that. It was supposedly liked by the Germans mostly because it could hole a T34 head on. But it still had the range/accuracy issues that most heat rounds had at that time.

In that chart from December 1942, it shows that Pzgr 40 for the Pak 40 are basically gone at that point. 'Bestand' means available currently or Stock. They shot off 5K in December though, so it was really a minority type compared to HE or AP or Heat. The Pak 40 'fleet' is also small at this time.

It is interesting that the Pak 41 'squeezebore' weapon is actually stocked with (W) rounds and using them. I always theorized that they would use these first as ranging rounds that could do some damage and stop a tank. The Tungsten carbide rounds are then used to finish that tank off.



Mobius -> RE: German 75mmL43, L48 and L46 velocities (7/20/2016 5:08:53 PM)

quote:

ORIGINAL: Elron Hubbub
It is interesting that the Pak 41 'squeezebore' weapon is actually stocked with (W) rounds and using them. I always theorized that they would use these first as ranging rounds that could do some damage and stop a tank. The Tungsten carbide rounds are then used to finish that tank off.
Maybe to scare the crew? In Middle East wars some Syrians bailed out of their perfectly good tanks when they were being pinged by Israeli Centurion ranging machine-guns knowing that a 105mm round was soon to follow.

I was hoping if we ever have a new PCO update or expansion HEAT shell evolution could be included. But, we haven't come up with a clean way to format this, which does not involve updating every single gun xml.




Elron Hubbub -> RE: German 75mmL43, L48 and L46 velocities (7/20/2016 5:24:47 PM)

There is a pic that shows a 7,5 cm KWK 40 HL/C that appears to be from january 1944. The powder date code is from the middle of 1943.



[image]local://upfiles/52248/91A9E48601D04674A5A32DD96D656D94.jpg[/image]

The Soviets were big users of light tanks. I suppose post-Kursk they cut back on them and used lend-lease tanks like the British Cromwell (57mm) in that role. So, HEAT and W (iron) rounds could take out light tanks easily and also other light vehicles like armored cars without using the expensive AP39 or AP40 rounds. A HEAT round on a SU76 would have been quite a sight.



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