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Mobius -> RE: German 75mmL43, L48 and L46 velocities (9/1/2016 2:45:09 PM)
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Top graph.
I had a 1943 Aberdeen graph but did not post yet as it has some parts missing. I filled them in and found that this must have been the graph the O.B. used to make their table. This has different ballistics for the KwK 40 than the 1945 Aberdeen table (post #213). The graph of 1943 shows the KwK having a ballistics coefficient of only 1.929. The 1945 graph has different 75mm KwK/PaK 40 guns having better coefficients ranging from 2.241-2.353. This looks like further testing gave the guns less loss of velocity and longer range penetration than originally thought in 1943.
quote:
O.B./43/CV.12 May 25,1943
shows for 2400 f/s muzzle velocity (731.52 m/s) of 14.81 lb. APCBC shell ("MV as tested by trial in KwK 40") at 0 and 30 degrees deflection:
2400 f/s penetration 121/102 mm,
2000 f/s (609.6 m/s) 98/83 mm,
1600 f/s (487.68 m/s) 75/63 mm.
Based on this graph 2000 f/s is at 975 yds and 1600 f/s is at 2087 yds.
[image]local://upfiles/21308/FC4CB8431D4E4028947893BE300B5263.jpg[/image]
Bottom graph.
Using the ballistics per the 1943 Aberdeen table I compared the O.B. 2400 f/s data (blue) to the 75mm/L43 all sources data collection (red) and it falls almost exactly along the average of the data. (The data collection does include the earlier not so good data with later data.)
I've called these graphs 'Aberdeen' graphs because the 1945 graph matches the Aberdeen table data and uses the 50% perforation criteria (US Naval Ballistics standard) but I don't know who actually produced them They have the style of some British graphs and have reference to some O.B number. And the dates are in the European style. Maybe UK and US jointly?
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