WW II Ballistics Tank Gun Penetration - France

I haven't found a French penetration criteria   I also haven't seen any proper firing tables or ballistic graphs.   There are often only single points of penetration at range.  Most firing tables must use the ballistics to compute penetration at ranges.  Since none of this exists I will use the ballistics of similar shell of other known guns.  Together with known data like weight and muzzle velocity I use the NaaB2 program to generate firing tables for guns of 37mm and greater.  So the following data is calculated using Nathan Okun's HCWCALC formula.and Robert McCoy's ballistics.   This checked against the few data points available.

Gun ballistic models come from US 37mm AP, APC and APCBC shell models.  US 57mm AP and APCBC shell models.   US 75mm AP and APCBC-HE shell models.

There is a very large difference between the French data on the performance of the 47mm/L53 and the German data.  The penetration according to France is more than 40% higher than the German evaluation.  For example according to the French Ministry of Defense the shot should penetrate 89mm @ 0° @ 500m.   But the German data gives it only 50mm @ 30° @ 500m.  This is a solid shot with a thin AP cap.  So would not be a weak shell unless it shattered on thick armor.  The penetration data here is the average of both German and generated data.

There's a question of the muzzle velocity of the 75mm/L17.1 APHE.  A couple of sites have it as 475 m/s.   Which seems exceedingly high given it's shortness.  This may have come from some German records.   But, a French site has it as 220 m/s.  Second French site.    If anyone should know it is the French.   If you don't believe those check out the  7:42 on Chieftains video.

(*)   If APHE was used in this howitzer this is the calculated penetration.
(**)   If APHE was used in this howitzer this is the calculated penetration for a MV 385 m/s.
(***)   If APHE was used in this howitzer this is the calculated penetration for a MV 475 m/s.

WW II Ballistics Tank Gun Penetration - Italy

The above is a calculated firing table using NaaB2.  In it I am assuming that the projectiles have soft AP caps.  37mm and greater generated by formula in HCWCALC STS Armor Penetration Calculation Program.  A reminder is that this program uses a M79APCLC as a basis.  It is calibrated from the US M79 solid steel projectile.  It assumed it is perfect and indestructible. Thus would have a shell quality of 1.0.   From there HCWCALC introduces energy loss due to AP cap and windscreen destruction. This would reduce the Ballistic Limit.  When calibrated against a weaker walled shell with a cavity for HE the shell quality would have to be lower.  Thus the ballistic limit is again lowered. The formula does not include nose break or shell shatter.  That would have to be determined on a case by case basis.

The effetto-pronto (E.P.) weren't considered HEAT shells by the Italians though they had similar construction.  They seemed to produce a slug that affected the armor like a HESH war-head rather than HEAT shell.  This may be considered an explosive formed penetrator.  Though this 'penetrator' acted more like the bullet of the Polish wz. 35 AT rifle than a modern EFP.  The penetration number is not necessarily a complete penetration but a thickness where behind armor effects are obtained.  In fact it was a broken HEAT shell which had good results.   Once the slow acting base fuse was replaced with a German style fast acting nose fuse the E.P.S. worked as a proper HEAT shell.

WW II Ballistics Tank Gun Penetration - Poland

Early war AP caps seem to be of poor design.  Some like the French were quite thin and may not have worked very well.  Others were rather large and elongated to help ballistics.  They may have broken off when encountering highly sloped armor plate though most tanks of the time had vertical armor.  Still others like the US 37mm M59 and German 50mm Pzgr. 39 while aiding penetration may have hindered ballistics.