Make projectile wobble on impact

I have a scene where javelins are landing on the ground. I’m using projectile movement for the motion and I’d like to trigger a rotational wobble using the ‘On Projectile Stop’ event so that they spring a bit in one axis on impact.

I’ve been trying to achieve this with the ‘Vector Spring Interp’ node, but really I’m not very sure what I’m doing or how this node functions! It seems like an easy thing to do but I’m a bit out of my depth. Perhaps this is the wrong way to go about it?