Im certain this is getting anoyying but @JeremyECrawford if I Cast the spell Catapult and used a flask of alchemists fire as the amunition would I deal both the spell and the Fire damage, just the spells damage, or just the. Flasks damage?
— Morgran… IRONHEART!!! (@Gentleman_Boe) February 13, 2018
The catapult spell deals only its damage, not the damage of an object you hurl with it. However, if you use the spell to hurl a breakable object, like a flask of alchemist's fire, the DM might rule that the thing does break. If so, follow the rules for the breakable object. #DnD https://t.co/GDOdL5JSTP
— Jeremy Crawford (@JeremyECrawford) February 13, 2018
To be clear, Alchemist's Fire doesn't have rules for it breaking not as part of an an attack roll; how would its breaking function when no attack roll is involved?
— Thomas "You Can Call Me Tom" (@thomasabarry1) February 13, 2018
A DM might decide that a flask of alchemist's fire breaks as a result of something other than the attack in the flask's rule. If so, I recommend dealing the fire damage, but don't treat the delivery of that damage as an attack that hit, since no attack roll occurred. #DnD https://t.co/smmpvGjvPn
— Jeremy Crawford (@JeremyECrawford) February 13, 2018