Make a projectile spawn a particle exactly where it lands

I've made a custom throwable similar to a snowball but cant see how to spawn a particle that shows it "breaking" exactly where it lands.

I've tried "spawn particle at x y z" in the "when projectile hits block" procedure with some math but that just spawns it in the middle of the block it lands on, not the actual landing position like a snowball does. Already made the custom projectile and particle but it never spawns where I'd like it to be.

Any tips? 

Thanks.