Slitherine

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ORIGINAL: Mobius

page 23

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ORIGINAL: Yoozername
Yes, the Germans did add 5% velocity (and what ever that powder amount works out to...). It is called out in BIOS as n%.

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ORIGINAL: Yoozername
http://www.scribd.com/doc/105592130/1973-afv-g2-volume-4-no-2
Here is the oft-quoted Mark Diel information. Considering his sources, it is not really that informative.

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by M. » 27 Apr 2006, 16:48

That's a wrong approach.

The 7.5 cm Pzgr. Patr. 39 Pak 40 had as propellant 2,75 kg Digl.R.P. –G 1– (625·3,8/1,3) + 20 g Nz.Man.N.P. (1,5·1,5). When fired by the 7.5 cm Pak 40 with a barrel lenght of L/46, a gas pressure of 2840 at was created resulting in a muzzle velocity of 750 m/s.

The 7.5 cm Pzgr. Patr. 39 Kw.K. 40 had as propellant 2,430 kg Digl.R.P. – G 1 – (370/420·3,8/1,5) + 20 g Nz.Man.N.P. (1,5·1,5). When fired by the 7.5 cm Kw.K./Stu.K. 40 with a barrel lenght of L/48, a gas pressure of 2750 at was created resulting in a muzzle velocity of also 750 m/s.

You can easily see that the different propellant type for the 7.5 cm Pak 40 ammunition created a higher gas pressure compensating the shorter barrel. The guns had not the same barrel length, the ammunition got different propellant types and weights to compensate this.

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"A.P.C.B.C. May Become Most-Used German Pak 40 Ammunition" from Tactical and Technical Trends
An intelligence report on German Pak 40 antitank ammunition in WWII, from Tactical and Technical Trends, No. 51, October 1944.
[DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]

A.P.C.B.C. MAY BECOME MOST-USED GERMAN PAK 40 AMMUNITION
German abandonment of the use of hollow-charge projectiles and AP 40 tungsten carbide core ammunition for the 75-mm antitank gun Pak 40 is indicated by reports from United States observers in the field. This, it is expected, will be followed by adoption, as the most common type of ammunition. of the 14.96-pound armor-piercing capped ballistic cap (A.P.C.B.C.) with a muzzle velocity of 2,600 f/s and the 12.5-pound high explosive with a muzzle velocity of 1,800 f/s.

General characteristics of the 75-mm German antitank gun Pak 40 are: Weight in action, 3,040 pounds; barrel length, 126.14 inches without muzzle brake, and 145.75 inches with muzzle brake; ground clearance, 13.8 inches; height of shield, 48.6 inches; diameter of wheels, 35.43 inches; elevation, -5° to +22°; traverse, 65°.

The welded tubular trails of the weapon are frequently found on medium-caliber German guns manufactured or modified within the last 18 months. The gun shield is a new design of two 4-mm spaced plates and is probably proof against small arms up to, but not including, 20-mm armor-piercing ammunition. Hand or semiautomatic operation is provided.

Previous references to this weapon were published in TACTICAL AND TECHNICAL TRENDS. No. 18, page 4 and No. 25, page 9.

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ORIGINAL: Elron Hubbub
Yes, it has second hand information. And, any, is too much. Ample does not make it any better.

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6. When the kannon 40 was introduced in April 1942 there was a shortage of ammunition for it. The new, stronger armor piercing shells Pz. Gr. 39 with a small cavity (17 gram explosive charge) were not available in sufficient numbers. What was available were armor piecing shells, the K. Gr rot Pz., used by the short 75mm cannon. These were fitted onto the large cartridge used in the Kannon 40. Some sources refer to this round as the model 38 with red band AP shell. Or, Pz. Gr. 38 rot, or even 7.5 Gr. Patr. 38 KwK confusing some people into thinking that there is an error and should be the HEAT shell Pz.Gr. 38 HL or Pz.Gr. 38 HL/A.

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ORIGINAL: Elron Hubbub

Archive Awareness: German experience in 1942
This website, which you cite, contradicts your theory. That is, it is from June 1942, it shows that the KWK 40 L43 (and StuK 40) were firing PzGr 39. There are no L48 weapons at this time. The actual number of KWK and StuK 40 weapons that were available in summer 1942 was actually very small. Your theory would then revolve around the inability to make the shorter cartridge cases. That would be incredible.

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Report of the NKV Special Laboratory #101-1 on the topic of STUDY OF CHARACTERISTICS OF STRIKING A T-34 FUEL TANK WITH AP-HE OR CUMULATIVE (HEAT) SHELLS OF THE GERMAN FASCIST ARMY
Responsible: Rozov, Kaminskiy, Shurov
"The first test of the models happened on December 12th, 1943, from a 75 mm model 1940 ballistic cannon, from 30 meters. During these tests, the fuel tank was fully filled with diesel fuel, according to comrade Afonin's letter from December 5th.
8 model 38 shells were fired, as well as 5 model 39/40 shells, and 5 armor-burning (HEAT) shells."

When the fuel tank was hit by fragments of m.39/40 shell they were slowed abruptly. Many fragments did not penetrate.
Conclusions: 100% filled fuel tank of T-34 tank cannot be a source to inner explosion of T-34 tank, but even serves a protection from fragments of armor and cores of m.39/40 shells.

[report continues]

The effect of a detonation of a 75 mm AP shell with the red ring, equipped with 80 g of TNT and a 20 g detonator, is quite different. The explosive force grows several times over. The overtrack hull seams burst, and the roof of the model is deformed.
Conclusions:
The best ratio for detonation of T-34 fuel tank is when it's 10-15% full and AP shell m.38 bursting inside. Burst causes immediate detonation fuel's vapor which adds to shell's explosion, multiplying it by 2-4, which corresponds with effect of 105-122mm AP shell.