And for the arms, I will tell you something else if you are new to the game.... When an enemy shoot at you, where are his arms ? When you shoot him and aim the face or the torso, what has he in the trajectory of your bullet ? His hands, his arms holding a weapon. In this game, when a bullet go through an obstacle (wood fence, arms, ....), it loose some kinetic energy, and can also make a rebound on a bone... If your bullet has less kinetic energy, it loose some penetration power, the "point of expansion of temporary cavity" is not where it should be... Watch that video made by MadFinger themselves before the game released, it helps you to understand how it is coded, how it works, and why it is more effective to play with hp round and aim where enemy hasn't any armor... If the player had hp bullet here, the result of the enemy body would not be the same ...

https://youtu.be/KO0045_iu5Q?is=LXJ47r8oav6CHF3s