I’m not confident that I completely understand how penetration works in the new system, so I did some testing with various projectile weapons. I haven’t crunched the numbers yet, so I’m not sure what it all means yet. Feel free to analyze the data! And if you want me to test other aspects and/or weapons with this setup, let me know.
Little boy:
Judge:
Elephant:
Executioner:
Fatman:
Avalanche:
Note that the avalanche removed the leg it was aiming for, so the number reflect that. At this point I went back and tested the previous cannons with dual weapons. Most of them took off a leg on the second volley.
Kaiju:
(Kaiju also removes a leg with one volley)
Yongwang:
Astraeus:
Astraeus is the only weapon I tested that can fit between the invisible hit box between two legs. I assume that scorpions and medians can too:
Stillwind:
And if you shoot a Stillwind between the legs, the explosive radius will hit the cabin:
I think most of the cabin damage we see with the cannons is explosive damage. The legs have enough durability to detonate the shell, and the pass through allows the explosive radius to hit the cabin.
This means that for a weapon like judge, the explosive radius is too small to reach the cabin when shooting through the length of a leg, but if you shoot between the legs, it will damage the cabin:
I like the efforts, but I’m not sure what I’m looking at, the experimental protocol, or what we’re testing. If you wanna see what goes through a Gerrida, I suggest placing an Ampere gen behind it, and keeping the whole target far away from the cab or structural parts. You see yellow/it pops, it went through.
Are you saying the cabin is too close to the legs to be able to see if any of the bullet damage is making its way through?
If so, maybe you’ll find this more interesting:
Judge firing at lots of pass through parts, with big gap before the cabin.
At ten blocks, looks like cabin takes most of the damage:
Extend the distance though, and the pass through absorbs it all:
But, if you remove most of the pass through parts, the shell seems to be able to hit the cabin, even with the huge gap:
This is with an eight block gap between the cabin and where the legs attach. Not sure if the total distance once you add in the length of the leg:
I posted three examples, because of the variety. One of them made it between the legs, and I think the white damage in that shot is probably the gun getting hit with splash damage. And in the two examples where the legs absorb everything, the smaller damage one was aimed through one leg, while the larger one was aiming between the legs, hitting both.
Odd that in the example you have, the Fatman (169-56), which is supposed to be the upgrade, performs worse on cabin damage than the Little Boy (140-89).
I have little hope of actually understanding all this. 
Well, that might not be such a bad thing for fatman. It does more bullet damage, which means it will go deeper into a build before exploding. Makes it more likely to pop a buried generator.
But little boy’s explosive radius makes it pretty effective in the range you’d play it in.
