7.5cm PaK 40 L/46

[TreadHead]

In the German spob016, the 7.5cm PaK40 (Weapon 052) should be L/46 instead of L/48. On the surface, the 2 calibers length difference doesn’t seem like much, but the devil is in the details. Below the reasons outlined next, I have some recommended changes.

The PaK40 L/46 shares the same barrel as the KwK40 L/43 (and StuK40 L/43). This was a progressive twist barrel. The difference in the measurement of the length is because it includes the chamber to the face of the breech block. The projectiles were the same, but the case was a third longer and without shoulders on the PaK40, and with more powder to pack more of a punch. The turret mounted KwK40/StuK40 needed a shorter case to facilitate being handled within a turret, and have a shorter recoil stroke.

The L/48 barrel had a uniform twist, and was only marginally better in performance than the L/43. The lower pressure of the uniform twist barrel would be offset by the extra length. Its practical advantage was that it was simpler & cheaper to produce. There are a number of ballistics table resources, but after wading through the ones that appear to carry forward inaccuracies, WWII Ballistics Armor and Gunnery by L. R. Bird and R. D. Livingston seems to be the most reliable. They show the L/48 being just 10m/sec faster than the L/43, whereas the PaK40 L/46 was 50 m/sec faster.

There is a good discussion on the three guns here: http://forum.axishistory.com/viewtop...uzzle+velocity

Note also that the KwK40 and StuK40 differ in the mounting and breech configurations, but in ballistics terms are the same. Likewise, the Pak39 L/48 used with the StuG IV and Hetzer fired the same round with similar performance (and these vehicles are in the game with Weapon 050 : 7.5cm StK40 L48).

Now, with all that said, here is what I’d recommend as changes in WinSPWW2 (see the attached spreadsheet for tables supporting the following points):

-- Weapon 052 should read “7.5cm PaK40 L46”, and the Accuracy value should be increased from 12 to 13.

-- Weapons 047 (7.5cm KwK40 L48) & 050 (7.5cm StK40 L48) should have the AP Penetration reduced from 13 to 12 and the Sabot Penetration reduced from 17 to 16. to bring it on par with Weapons 046 (7.5cm KwK40 L43) & 049 (7.5cm StK40 L43). The net difference between the L/48 and the L/43 would then just be the Accuracy value (12 vs 11).

-- There are 23 Units that mounted a 7.5cm PaK40 instead of the StuK40 or KwK40 currently shown in spob16. These are Marders, halftracks, armored cars, etc. Weapon slot 1 should have Weapon 052 for the following Units: 044, 045, 046, 047, 075, 170, 385, 386, 956, 957, 960, 961, 962, 964, 965, 967, 970, 971, 972, 973, 974, 975, and 980.

-- Note that matching changes are needed for the following other OOBs in WinSPWW2:
spob01 - Slovak Republic for Weapon 047
spob02 - Poland needs for Weapon 047
spob04 - Italian Socialist Republic for Weapons 046, 047 & 050
spob06 - France needs for Weapon 047
spob09 - Polish LWP for Weapons 047 & 050
spob11 - Soviet Union for Weapons 231 & 237
spob19 - Bulgaria needs for Weapons 047, 049 & 050
spob20 - Yugoslavia for Weapons 035 & 039
spob33 - Spain for Weapons 045 & 047
spob34 - Italy for Weapons 046 & 047
spob35 - Finland for Weapon 047
spob37 - Czechoslovakia for Weapon 047
spob38 - Hungary for Weapons 047 & 049
spob39 - Romania for Weapons 045 & 047
spob42 - Blue for Weapon 044
spob43 - Red for Weapons 045 & 047

-- Also note that matching changes are needed for the following OOBs in WinMBT:
obat01 - Syria for Weapons 248 & 249
obat37 - Czechoslovakia for Weapon 237
obat38 - Hungary for Weapon 226
obat39 - Romania for Weapon 233
obat53 - Switzerland for Weapon 085
obat65 - Finland for Weapon 088
obat87 - Bulgaria for Weapon 231


Ross