Do special types mundane ammunition, such as Alchemist fire crossbow bolts , multiply on vital strike as part of the increase to damage?
I believe I would treat it like a Flaming enchant on a weapon. Which doesn't get multiplied on a Vital Strike or a Critical Hit.
Benefit: On a successful hit, fire bolts deal normal damage plus 1d4 points of fire damage.
Note: Alchemical fire bolts do not cause any splash damage, and the fire burst isn’t enough to ignite targets (unless they are particularly flammable).
It's non-magical, which I think means it works with abundant ammunition.
But the damage comes from the arrow, and is not additional damage like that from feats such as burnburnburn or effects such as flaming/fireforged steel.
It would be peculiar if it did get multiplied by Vital Strike. As I mentioned the Flaming Enchant on a bow/arrows deffinitely doesn't get multiplied by Vital Strike. If the alchemist fire arrow did it would mean with just Vital Strike you would do 2d4 (avg 5) fire damage versus the 1d6 (avg 3.5) damage from Flaming. And that just doesn't seem right to me. Furhter, once you got to Greater Vital Strike you would deal 4d4 (avg 10) damage....yeah....no.
It would be peculiar if it did get multiplied by Vital Strike. As I mentioned the Flaming Enchant on a bow/arrows deffinitely doesn't get multiplied by Vital Strike. If the alchemist fire arrow did it would mean with just Vital Strike you would do 2d4 (avg 5) fire damage versus the 1d6 (avg 3.5) damage from Flaming. And that just doesn't seem right to me. Furhter, once you got to Greater Vital Strike you would deal 4d4 (avg 10) damage....yeah....no.
4d4 is really laughable though, but I get your stance, I just don't know if the 1d4 damage would count as it comes from the weapon itself and not a magical effect.
now another question
Endless Ammunition
Can this be used to make any sort of ammunition on a whim?
I'm not saying the damage is overwhelming, it just doesn't make sense that flaming (which is a more expensive and magical enchant) is incapable of being combined with vital strike, but that the less expensive alchemical fire bolt is. And when combined does more damage than flaming.
As ar as endless ammunition is concerned, you create only normal ammunition. It is a free normal arrow, nothing more.
Now, abundant ammunition on the other hand would create duplicate non-magical ammunition for as long as the spell lasts. This includes your alchemical arrows/bolts as well as adamantine, silver, mithral, etc.
Relevant rule:
Multiplying Damage: Sometimes you multiply damage by some factor, such as on a critical hit. Roll the damage (with all modifiers) multiple times and total the results.
Note: When you multiply damage more than once, each multiplier works off the original, unmultiplied damage. So if you are asked to double the damage twice, the end result is three times the normal damage.
Exception: Extra damage dice over and above a weapon's normal damage are never multiplied.