AP weaponry

[Aemilius Paulus]

Well, maybe that is the problem of the arrow's low weight and fragility. It is like comparing a dagger and a club. If you stab or slash a guy wearing maille, he will not get hurt at all, despite the fact that in the stabbing motion of a dagger, all of the energy is concentrated in that one millimeter point. There is simply not enough weight and momentum behind the dagger point to 1: pierce the maille and 2: to transfer shock waves significant enough to hurt the wearer. A club or mace on the other hand, can generate enough shockwaves to crush the body of the wearer, even without actually piercing the armour. Same is with the bullets and rocks launched from the sling. They never pierce the armour, but either shatter or severely dent it, at the same time pulverizing the flesh, bones as well as internal organs. It is very hard to pierce maille or plate armor with a kinetic projectile launched by physical means. Bullets can do it, but they are propelled by the force of a violent chemical reaction.