[Crni vuk]

well what was used many times as well was the APHE shell ~ but it was not orking on the principle of shaped charges or in other words HEAT they came later. At least in the begining when the velocity of anti tank guns was not that high. Expecialy the Germans made here quite good shells. It was basicaly a armor pearcing shell filed with explosives designed in a way that it should penetrate the enemy armor and explode inside not sure if they had a fuse for that but I think it started with originaly with naval guns as they needed both penetration and explosives to get a ship penetrating it alone would not always sink it. Precise methods of differentially hardening the projectile were developed in particular by the Germans for example so it could deal better with the shock of the penetration achieving much more success with their shells that way so premature explosions on impact have been less. Later they had to move toward shells with a hard core cause of increasing armor on the enemy side which required guns with high velocity and thus different materials and shapes of shells as the APHE shells did not worked so effectively with high velocity anti tank guns. So for example the APCR is a shell with some aloy on the outside and a very dense material as core or "second shell" inside increasing the penetration quality a lot (tungsten usualy) I think 3 times the size of the caliber even on long ranges compared to the usualy 2 or 1.5 times with APCBC

I wish I could get the books about it as there are many details behind it. And I am not a pro when it comes to that. So some details by me might be eventualy misleading.