Hi David,
I know this is a very old question, but I couldn’t find an easy answer to this on any other questions, so I thought I should answer for posterity’s sake.
The API page for the IgnoreActorWhenMoving call says
“Components on the other Actor may also need to be told to do the same when they move.”
I just coded up an example of an actor spawning a projectile, and I called IgnoreActorWhenMoving on the projectile’s static mesh, but I also used MoveIgnoreActorAdd on the Actor responsible for spawning the projectile to make sure they don’t collide with each other.
ARadianceProjectile* proj = GetWorld()->SpawnActor<ARadianceProjectile>(Location, Rotation, SpawnInfo);
this->GetControlledPawn()->MoveIgnoreActorAdd(proj);
I have that code in the Controller for the actor responsible for spawning the projectile, and it seems to work great.
Hope this is helpful.