You seem to be entirely correct.

I'm using this to extrapolate some values of weapons that only exist in normal damage varieties and the results are very interesting. Add 61 for weak damage, then multply by 16% to find resisted damage. Adding 61 creates a very consistent increase in damage value, too, which definitely increases linearly.

Sorry, Bopp. I have to call shenanigans on your exponential increase theory.

Done some more work on the sheets. They are now split into
-Sword chart
-Gun chart
-Bomb chart

So you don't have to scroll past all those bombs and swords to find the damage values of your alchemer, say.

We've done lots of science on the numbers gathered, and we have found some more interesting points of note.
-Resisted damage seems to have base damage reduced to 16% (50% for split-damage weapons), but then damage increase works linearly with a lowered value. Each step of damage increase appears to be lowered by this same amount, so resisted damage behaves the same way as undefended damage, but with smaller numbers.
There are A LOT of weapons with identical damage values:
--Everyone knows that BTB = Final Flourish. But did you know both of those are also identical to Leviathan? Right down to the charge damage.
--Cold Iron has a bit more damage than Flamberge and Rigadoon, but their charges are identical again.
--Sudaruska, Triglav and Warmaster Rocket Hammer all share damage values. So stop comparing WMH to Divine Avenger, already.
--Valiance shots have the same damage as Wild Hunting Blade and Dread Venom Striker's non-ghost hits.

And that's just swords. There are basically only four distinct guns, in terms of damage values.
--Iron Slug and Callahan's charge share damage with Biohazard. Neutralizer is stronger, and unique.
--Expanded Polaris share damage with Nova and Umbra Driver. We already knew this. Expandid Supernova, however, shares damage with Iron Slug.
--Unexpanded Polaris/Supernova share damage with status alchemers. We already knew that too, but did you know Catalyzer falls into that category, too? Poor Catalyzer.
--Polaris charge shares damage with Nova and Umbra.
--Blitz Needle, Sentetza and Argent Peacemaker share all damage. Regular shots are alike, and each shot from the Blitz charge is as strong as one hit from the Antigua birdies. The shots preceding the bird is just regular shot damage. Don't Antiguas root you in place longer than Blitz?
--Volcanic Pepperbox and Plague Needle share damage with Dark Retribution.

--Electron Vortex share damage with Haze Bombs.

For the heck of it, I also calculated what each gun and bomb would've done before the universal buff. I'm not sure I did it the correct way.

Go science!

Ah, yes. They were swapped.

Thanks for notifying me, it's been fixed.

It's Nitro and Dark Briar Barrage. They have identical damage values for neutral.

But yes, actually! For any weapon that only comes in normal damage type, you can simply add 61 to get damage value you'd theoretically get if that weapons was specialised.

You're bit off. Your problem is you assume neutral damage to be base damage, but I think the truth is in damage against weak targets being base damage. Let's examine DBB again:

Effective: 275, 289, 302, 316, 329, 342, 356

Check the jump between each damage bonus:

356 - 342 = 24
289 - 275 = 24

See that? Damage scales linearly, but not at a neutral level. At neutral damage, the damage scaling seems more logarithmic due to the the defense working linearly. This means that damage bonus makes a bigger difference for neutral damage than weak damage. Here's how I figure the algorithm goes.

(A) An attack has a certain amount of "base damage". I believe this number to be somewhere in the low end. If this was my game, I'd put it somewhere between 0-32. The reason I believe this is because of all the attacks that share damage values. This point is merely speculation though.

(B) Some magic space formula is applied to increase damage with each depth. This scaling is completely linear within each stratum, and even within tiers. The only exception is that the increase is considerably lower for stratum 6 than stratum 5. For proof of this, see the bottom of the google spreadsheet for bombs, where I recorded damage for BAB at every floor.

(C) For each level of damage bonus, add about 5%. Again, this is completely linear. However, for some weapons the proportional bonus is higher. The bonus seems to be relatively higher for weapons with less damage, and this works in favour of split-damage weapons as well as multihit weapons.

(D) If the targets is "neutral" towards the attack, subtract the set amount of defence the monster has towards the damage's type. At level 23, this is 61. Of note against is that this is a bit sketchy at low amounts of damage again. There is variance amongst weapons with low base damage such as Brandish (where each damage segment is low individually), shard bombs and handguns. Sometimes the defence is less but other times, curiously, it's higher. I have yet to make sense of it. Since this defence is mostly linear, however, it works in favour of weapons that hit heavily per attack, as they will suffer much less of a penalty against neutral targets. Split damage weapons, curiously, suffer no ill from it and will only get their defence subtracted once. Hopefully this is not how it works in Lockdown.

If the target is resistant towards the attack, multiply the base damage and the damage bonus by about 16%. The base damage and the damage bonus seems to be rounded up individually. That's more of a gut-feeling than a very close study of it. Grain of salt and all that.

The result is the final damage you see. To find a normal damage weapons "true" damage, you'll need to add neutral defense to it and can find the proportion for damage increase bonus from there.

Try plotting with weakness damage rather than neutral. I realise this isn't possible for hunting blade, but I guess try adding weakness "bonus" to it.