It was thought that some tests of German 75mm guns done at Aberdeen Proving Grounds. This was published in "German Tank and Anti-tank" by E. J. Hoffschmidt and W. H. Tantum IV. 1968. Below top is the Firing table of the 75mm/L46 with a MV of 792 m/s. As can be seen the ranges are in yards typical of US WWII methods where the armor hardness is normalized to 237 BHN. See page 33 for armor penetration criteria.
This table below is taken from a table page 196 of the same book. It only gives the penetration at 30° at 500 yards.
Mark Diehl apparently had the above data when he produced the tables below for AFV-G2 magazine. But, it looks like he mixed the yard ranges for meter ranges. Lorrin Bird has said he used this data to confirm his ballistics calculations on his book "World War II Ballistics: Armor and Gunnery". I don't know if this affected his final product.
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.
Table V has some interesting information like HE armor penetration. Making a comparison of velocities I wouldn't put a lot of credence in these Spgr. Patr. numbers being correct. For example it lists the 75mm/L24 Spgr. Patr. 34 penetrating 30mm when the terminal velocity is 420 m/s. Compare this to the 75mm/L48 30mm penetration at 2500m where the terminal velocity is 355 m/s. (That is using Bird's Ballistic "K" factor 2600.) My estimated "K" factor for the 75mm/L48 HE is 2363 resulting in a terminal velocity of 367 m/s @ 2500m. At best even using the 2176 "K" factor of 88mm HE shell (PDF) the terminal velocity @ 2500m would be 378m/s.
Moving on to actual firing charts (PDF) we do have the ballistics of the 75mm US M48 HE round (producing a "K" = 2188). While this shell nearly matches the aerodynamic shape of the German projectile it is heavier by about a pound and a half. Firing that at 550 m/s gives a terminal velocity @ 2500m of 377m/s.
Note- No result is near 420m/s.
Aberdeen (British Ordnance Board) tests Thanks to a posting on the World of Tanks forum I did find several Aberdeen looking Ordnance Board ballistic graphs of the German 75mm Pzgr 39 shell. The graphs were revised each year starting May 25, 1943 (image at right) to either correct errors or change standards. They are reminiscent of the 1943 German graph on page 43 as Aberdeen uses a graph with one continuos curve representing all 75mm guns.