I don’t fully understand this either. But after testing I can definitely say that when the Root of the projectile blueprint itself is not what is “handling” the collision, it doesn’t work. (examples below using projectile movement component with default settings except initial speed set to 200 for testing)
Example A)“Not Causing collisions_”
Default Scene Root
-Sphere Mesh
Example B)“Causing Collisions (no settings changed)”
Sphere Mesh
The issue lies with unreal engine not handling “nested collisions” in this case and also with projectile component not moving a scene component. I’m not sure of this but I imagine the scene component is not going anywhere when the example A above is fired, even if the projectile mesh is moving.
On another thread a user named RevOverDrive mentions this…(thanks Rev)
"Projectile movement will not move a scene component. Anything bound to the scene component will not move either. Thus your collision doesn’t move.
Proper projectile hierarchy should be:
Collision (parent component, aka root)
Projectile Movement Component
If you want any visual element (emitter, mesh etc) parent said component to the collision.
e.g.
Collision (parent component, aka root)
→ Static mesh component
→ Particle System
→ Audio Component
Projectile Movement Component"
end quote
Hope this helps someone! Cheers