Yes there is penetration and it is since Hel Cannon is available. Even sniper rifles can do so since first Backers Builds. Until full release it was working like multiple hits even with one projectile and it was best seen on Scylla who is an easy enemy to line up multiple body parts. But with Siren it is not so easy. Let me throw some image.
Before full release:
Trajectory A
It was possible to hit multiple body parts and projectile was doing damage to both body parts (here torso and left arm) and body part which took more damage was affecting unit’s general HP. Also before release shred value was applied before damage value for projectile weapons. In our example from picture (let assume current Siren parameters: 250 HP + 30 armor torso, 180 HP + 20 armor arm, and old Hel parameters: 180 force damage + 10 shred) Hel projectile would damage torso for 160 damage and arm for 170 damage, shreding 10 armor on each body part. General HP would drop by 170 HP.
Trajectory B
It was possible to hit single body part multiple times and projectile was doing damage each time (here tail two times) and sum of that damage was affecting unit’s general HP. In our example from picture (let assume current siren parameters: 300 HP + 30 armor tail) Hel projectile would damage tail for 160+170 damage, shreding 20 armor on this body part. General HP would drop by 330 HP.
In full release:
It looks like in full release two changes were made:
- Shred is applied after damage for projectile weapons (so now for all weapons)
- Projectile piercing through same enemy lose power (damage), so effectively first hit is subtracted from projectile overall damage (the same as with shooting through environment objects).
- lets now use for Hel Cannon 20 shred value from Leviathan patch.
Trajectory A
Projectile hits point 1 and deals 180 - 30 = 150 damage also shreds 20 armor. Now it doesn’t have enough power to go further (full damage was stopped by 30 armor and 150 HP). If torso would have been disabled then projectile would hit arm in point 2).
Trajectory B
Actually it is the same case as with Trajectory A. Projectile should’t move further after point 1. I wonder what would happen if it would punch through… Probably it would apply the rest of the damage. Lets now assume that tail has only 120 HP and still 30 armor. So Hel projectile would deal 150 damage (overpowering HP and disabling body part) + 20 shred. So in this moment tail stopped only 30+120 damage, so projectile still has 30 damage to do. And it hits tail again in point 2, where now it only has 10 armor and 0 HP, so it deals 30-10 damage also shreding last 10 armor. So overall damage would be 180 damage and 30 shred?
Conclusion
We can guess that I have encountered conjunction of trajectory B + A. So for some reason game recognized that projectile would hit torso 2 times (how?) and then hit arm. Algorithm stopped damage of projectile on first obstacle (correct), but forget to stop projectile and applied shredding, so calculated it again for torso and then an arm (which is incorrect).
That is why I put that statement:
Devs really need to check what is going on after hitting with explosives and high damage weapons.