hey widewing... i'd read up a bit more... most armor piercing is explosive... alot being designed to explode on a fuse delay when its inside the armor... during WWII the Brits had no APHE except for the 2 pounder
Indeed, you should "read up a bit more", and something beyond wiki. Aside from HEAT rounds, AP rounds were solid shot, some of which had a base-fuzed anti-material/anti-personnel bursting charge that would detonate after penetration. This charge had nothing to do with penetrating the armor, which you have argued....
"uhh...... yeah? they have shaped charges on the tips concentrating to a powerful explosion forwards. some charges have delays creating the explosion inside the armored unit but i believe no delayed AP charges were used in WWII" Note that this statement is contradicted by your follow-up comment at the top.
"they were also meant to force larger rounds to explode before the impact with the actual tank. the 5mm of armor would cause the AP round to explode early causing no harm to the tank."
Again, aside from occasional HEAT (shaped charge) rounds, the vast majority of AP rounds were solid shot (some with, many without a small bursting charge) that relied completely upon kinetic energy to penetrate armor.