Natural Attack Size Track

[Momar]

There seems to be two slightly different tracks for natural attack size progression. One is found in the text of the improved natural attack feat, while the other is under the strong jaw spell. Is one more correct than the other? The INA progression is the same one used in 3.5, and it's the same progression that weapons use. The summoner's eidolon seems to follow the strongjaw progression, judging from the eidolon's slam. Both the eidolon and strongjaw are from the APG, meaning that they are more recent if it matters.

[Are]

Apparently the strong jaw spell uses the same progression as Dragon attacks, where 2d6 becomes 2d8 rather than 3d6.

IMO, they should both use the Improved Natural Attack progression, as that is equal to weapon size progression. It doesn't make much sense to have two different size progressions.

[Bobson]

There are two progressions, and this is actually a case where d20pfsrd is slightly misleading, and the official PRD or the physical books are more accurate (sortof). Strong Jaw - you'll see that there's no actual tables, just the "two sizes larger" language. Based on that language, you go to the bestiary rules for Natural Attacks, which has that table. Anything that changes the size of you or your natural attacks uses that table unless specified otherwise. This is why dragons (and all other monsters) progress the same way.

The Improved Natural Attack feat specifically has its own progression, which is only used for calculating the new size after applying INA (unless you have another feat/ability/spell which specifically refers to the INA progression). The wording of INA is misleading in this case, because of the differences (which is mostly the question of what 2d6 sizes up to), and they really should be reconciled, but the table is the primary source.

That being said, in my games we use a hodge-podge of sources for sizing (monster size, INA, and weapon sizing) whenever there's any question about which to apply, since they're all pretty close, and they all cover things the others don't.

[Are]

The strange thing is, in 3.5 the INA progression was as it is in Pathfinder, but it also exactly matched the "Increased Damage by Size" table. The odd man out was the Dragon progression (it was the only progression in 3.5 that had 2d6 -> 2d8).

Pathfinder's "Natural Attacks by Size" table matches the Dragon progression rather than the other way around, leaving the INA progression the odd man out instead.

I couldn't say why this particular change was made (I think 2d6 -> 3d6 -> 4d6 makes more sense than 2d6 -> 2d8 -> 4d6), but it seems to be deliberate.