Is there already an event for when a projectile hits something (hits the ground)?
Yes, CollideEntityEvent for when something collides with an entity and CollideBlockEvent for when something collides with a block.
You can check the cause (event.getCause()) to see if the collision was caused by a projectile
The CollideBlockEvent doesn’t seem to get triggered currently. Maybe it hasn’t been implemented yet?
Isn’t implemented yet. See this tracker:
Alright, thanks.