17/08/2019 at 2:04 am #9902GamecksParticipant
Just a statistical comparison regarding the max penetration values of the British 17 lbr of all types vs the German KwK/PaK 42 on all related vehicles. In the current build the maximum penetration values for the 17 lbr is listed as 162mm and the KwK 42 as 151mm. Both are firing APCBC by default, granted the 17 lbr shot is solid while the PzGr39 shot has explosives.
The penetration values for these weapons from 100m at a 90 degree angle with 50% success criteria – In this case we don’t care about APCR or other ammunition types. Steel types if changed will be recorded
PzGr39/42 (APCBC) 100m @935m/s: 185mm penetration
Shot. Mk 8 (APCBC) 100m @884m/s: 174mm penetration
vs. case hardened this increases to 187mm however seeing as steel types are not taken into account the first figure is more universal.
So all in all it seems the values, while accurate are taken from different ranges with different ammunition types in mind.
(Bird, Lorrin Rexford; Livingston, Robert D. (2001). WWII Ballistics: Armor and Gunnery. Overmatch Press.)
<cite id=”CITEREFBirdLivingston2001″ class=”citation book”>
17/08/2019 at 10:20 pm #9926MeatShieldNZKeymaster
I have quite different data for the 7.5cm StuK42 Pzgr 39/42:
Peter Chamberlain, Hilary L Doyle and Thomas Jentz all have it at 138mm versus 30 degree plate (100m)
Bird seems to be out on his own on this one, so we decided to go with the majority rather than showing possible bias.
I have taken this approach with all of my research to avoid bias. As you can appreciate we are dealing with very old documentation that sometimes gives quite different values. Not to mention the multiple different testing methods and definitions of a successful penetration.
Bird seems to calculate things differently to most of the other notable authors on the subject.
From my raw data on the 17 pdr APCBC I have 5.5 inches at 500 yards. To my knowledge this is the only actual close range post war testing figure that exists, we have simply extrapolated the data slightly differently than Bird resulting in the 10mm variance at 100 meters.
Thanks for taking the time to post but based on the above I am comfortable leaving the values as they are in game.
I hope that my explanation is enough to explain our reasoning.
23/08/2019 at 3:19 am #9953GamecksParticipant
Well this argument isn’t worth all that much but it seems that they are the values that are also used in War Thunder which seems to be the basis for most of the armor values in this mod. (specifically a pretty early version of WT) I’m not sure if this is true it’s just the conclusion I’ve drawn from word of mouth and the fact some of the values that are used (like 82mm accounting for slope max armor on the Panzer IV) are unique to said early version.
Regardless this is supposedly the reasoning behind the change in value: (Note this is speaking about the KwK 40 L/43 – 48 guns specifically but the table which I can’t figure out how to attach has the L/46 and L/70 listed so I assume this applies to all of them. So its very possible, seeing as WWII Ballistics is a more recent document, 2001, that it has calculated for these various errors. And I know its a logical fallacy to point this out, but I assume it’s been background checked to buggery seeing as plenty of games and other sources use it such as WT and RobZ mod for MOWAS. Anyhow please ask if you want to see any of the associated charts or any more background information. Thanks for putting up with my rambling.)
“I once thought this data originated at Aberdeen from US tests, but it appears not. The data closely matches British Ordnance Board graphs of German 75mm guns. The first appeared May 25, 1943 and were revised several times. (See British Criteria page 33) But, they apparently evolved to the present numbers. The ballistics of the gun were changed as well as the armor values. For example in 1943 the penetration at 2400 f/s was 121mm but in 1945 2400 f/s penetrates 132mm. I don’t know if this was all a result of normalizing the MQ target armor to US standards or changing the penetration criteria to be exactly like US NBL standards.”
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