7,62cm PzGr. 40

[Nabob]

The driving band dimensions depend on the need to withstand the forces of engraving and projectile rotation without failiure due to wear, shear, erosion or bending.
The force on the projectile is function of the pressure behind the projectile and changes with time / length traveled. So the equation (didn't say it is simple) is basicaly a strength calculation of complex shape and multiple forces. The empirical rule is that, if the result is larger than 30mm, two (or more) driving bands are used.

To answer Richards question, yes, the pressure is (but not only) dependant on the ammount, type and shape of powder grains.

@ Radmeer - the smaller powder charge does not make sense with AP projectile, even less with this expensive one. (The manuals say that the crew was allowed to shoot the Pzgr. 40 only after the Pzgr. 39 hit was not effective. (Wonder if this rule was followed.)

I will have to ask my alma mater for the formula

Bob

 

[Redmeer]

I know the formula, but using this round in shorter case makes no sense after all

 

[Nabob]

It makes the same sense as in the Pak case. The muzzle velocity is substentialy higher than Pzgr 39, the penetration on short distances is higher too.
The reason is to increase the probability of killing enemy tanks with the gun You are stuck with.

Bob

 

[Redmeer]

Yes, but remachning projectile to less-effective gun?

 

[M8owner]

This thread has been very helpful. I now know why this Russian 76.2mm high explosive UOF-350M round is marked with "284" on the case and projectile; it was captured and reissued by the Germans.

 

[marek_wawa]

Yes, but remachning projectile to less-effective gun?

Cheaper than making them all over again. Economics.

 

[Redmeer]

Ok. Keep believing.

 

[marek_wawa]

I will, unless you'll use some convincing aguments. Till now there are only doughts and speculations. You've seen some drawings and charts but still you refuse to believe they are real and correct -I totally get it, this is possoble. But still you don't have any hard evidence that our concepts are wrong. Be open minded, it's the best way to figure some things out.

 

[RichardB]

I have to say, I tend to agree with Nabob and Marek, in that it makes sense to send ammunition to the battlefield (or potentially machine, locally) than to send a captured guns in 10's / 100's back to a manufacturing plant for re-boring with specialist and dedicated tooling. It also makes sense to provide extra performance if possible.

Clearly we wont know until there is documented proof, but thats my 2c

Rich

 

[marek_wawa]

Guys, what would happen if the Soviets captured lots of german ammunition made for captured and remade F-22 Guns? Hmm? Could they use it in their own guns? I mean... well... you know, simple thinking of mine

 

[Nabob]

Interesting thought.
They used the bombs. However the only change there would be the fuze and special ring holding it.
Turning down a rotating band is more complicated. Then You would need new range tables.

There is not much info on captured german equipment used by the soviets. Or is it?

Bob

 

[RichardB]

Im not aware of the Russians struggling for materials, labour and equipment in the same way the Germans were from 1942 onward, so perhaps they simply didnt need to.
As I said before my theories are guesswork, but fit the senario.

 

[Redmeer]

https://en.wikipedia.org/wiki/Occam's_razor - interesting info for some members.

Data in this thread (Geschossringbuch, as well russian wartime sources about german ammo) clearly points at standard 7,62 Pzgr. 40 projectile. If you want to force strange theories without any data proof, keep going.

 

[RichardB]

Redmeer, this is an interest group not a dis-interest group.
Respectfully, would you mind dropping out of the conversation as you're adding nothing of value to it

I would like to understand if anyone has seen something similar, where a driving band on a standard projectile has been altered so a projectile could be used in a different weapon.. or is the concensus that these projectiles are perhaps experimental.

https://en.wikipedia.org/wiki/Open-mindedness - interesting for some, but not all, apparently.

 

[Burney Davis]

Gentlemen, lets not allow this thread to deteriorate into a bun fight. Speculation in the absence of proven facts is welcomed and everyone's point of view should be respected. The tone of comments made on this forum should be kept civil and as friendly as possible. Your understanding and compliance is appreciated.

 

[RichardB]

Apologies Burney,
I was hoping someone could shed further light by way of photos, drawings or other interpretations of why this was, or might have been done.. There are plenty of people in this group with vast knowledge.

Dave, sorry the conversation is dull, I suspect it'll remain a mystery

 

[greif]

I would like to understand if anyone has seen something similar, where a driving band on a standard projectile has been altered so a projectile could be used in a different weapon.. or is the concensus that these projectiles are perhaps experimental.

In the German manual D 435/3 which describes the marking of German ordnance you will find under Lfd Nr. 80 an example of machining of driving bands.
A free translation of the text given: German projectiles of which the driving band was machined to be fired from captured Polish guns, were marked with a white P above the driving band on 2 opposite sides of the shell body. This concerned the following shells: 7,5 cm K.Gr.Pz. (p) ; 7,5 cmK.Gr. (p) ; 10,5 cm F.H. Gr. rot (p) and 10 cm Pzgr (p).
The 7,5 cmK.Gr.Pz. (p) was also fired from the 7,5 cm Pak 97/38. So the driving band of the K.Gr. rot Pz was machined to be fired from the French barreled 7,5 cm Pak 97/38.

 

[greif]

The alteration was not always done by machining a driving band. Sometimes a narrower driving band was put on an existing shell. For instance the standard 7,5 cm Gr.38 Hl/B (width driving band 17,4 mm) was adapted to be fired from the 7,5 cmPak 97/38. This shell became the 7,5 cm Gr. 38/97 Hl/B (f) (width driving band ca.11 mm).

 

[Alpini]

@Marek_wawa: can you weight your shell? (complete weight Shell with tungsten core and cap)

 

[marek_wawa]

Alpini I will do so and post this tomorrow.