Speutogordoz

[Macilrille]

However, these very big spearheads are designed to dish out harm to unarmoured opponents.

Big, broad spearheads = max damage to unarmed, little penetration against armour; Pushing lots of metal surface through much metal surface is hard while against unarmoured you can make huge gashes slashing and stabbing with it). However, against horses it is an excellent option if these are unarmoured (which in that period and area they were).

Slender spearheads = max damage to armoured opponents, not much different to unarmoured (easier to push a small metal area through another metal surface, but you cannot in the same way make huge gashes with slender points).

So perhaps, no AP, but more damage?

Edited to add, Ludens already said that.