Setup:

* New empty game object under avatar's wrist (make sure the game object is at location 0,0,0 and rotation 0,0,0).

* IKFollower on this empty game object.

* New empty game object under the IKFollower object you just set up.

* Particle system on this second empty game object, set up to fire in a certain direction. (In my case, where the prop on the same wrist is facing.)

Now when you go in game, stand still and fire the particles around, everything seems to be working correctly.

But if you move backwards and forwards while doing it, somehow this ends up applying additional motion to the particle in the Y axis, even though you're not moving on that axis.

This essentially made IKFollower unusable for my use case for projectiles on a weapon, forcing me to revert to the previous workaround.