So there and then i've read that the germans had to face tanks that were pretty much imune to their dedicated AT 37mm and later 50mm guns early in the war ( B1 french tanks, KV-1 tanks, and the like ).
Then they would have to use artillery gun with direct fire, and the 88 flak gun.
Hence my question : Since the 88 flak gun was a AA gun, I assume the standard ammo used HE with shrapnels and a fuze, but this sounds quite inadequate to deal with armored targets. So Did the german expect to use the 88 as an AT weapon and had AP ammunition provided or were they using standard AA shells ?
Yes, the Germans had special armour piercing shells for their AA guns. The 8,8 cm Pzgr.Patr. armour piercing tracer round weighed 15.27 kg (slightly heavier than the 14.87 kg HE round), but was slightly shorter at 875 mm. It was equipped with a Bd. Z. f. 8,8 cm Pzgr. fuse.
Drawing of the shell in a Soviet encyclopedia of German ammunition
That is not to say that an HE shell of that caliber is not useful against armoured targets. Soviet trials of HE ammunition revealed very promising results with the 85 mm caliber. An 85 mm HE shell set to fragmentation action can penetrate 45 mm of armour at 30 degrees, and even non-penetrating impact from an 85 mm shell could cause hearing damage, damage the tank's suspension, optics, and other softer components.
Sources:
A.I. Kluyev et al, Nemetskiye Boyepripasy 1943
P. Samsonov, 76 mm HE
P. Samsonov, Under Pressure, Part 2
