Animation rigging query Help Please

I setup animation rigging on my first person arms and setup two bone ik constraints.My recoil script makes my weapon recoil and shake and i would want my ik arms to follow.I tried setting up a muilti parent constraint for the ik target of my arms to be parented to the weapon when the animation is playing.But the ik target does not move along with the weapon.
I tried setting up a cube with the multi parent constraint and it moves just fine along with the weapon.What am i missing here?

Edit: If i parent the ik targets to the the weapon and attach a rig transform component to it it works as expected.I was hopiong the same behavbioour to be achievable without actuallly parenting the ik target to the weapon and setting up a multi parent constraint to parent the ik targets to the weapon.
Any ideas anyone where i am wrong?