Left hand ik not move with pump action shotgun animation

Hi All,

I am figuring out a way to move my left hand along with pump action shotgun during fire but days passed still no luck.

The animaiton system I am using is ALSV4,
The solution I am thinking is:
Under the weapon skeletal mesh, create a Socket where the character want to hold the weapon, in this case, under the clip bone of shot gun, so when shotgun fires and plays the montage, this socket can move with it. Trasnform this socket trasnformation into bone space. Lastly, use the two bone ik node to move my hand to the effector location.

Create a socket under Clip bone of shotgun skeletal mesh.

In the animation blueprint, event blueprint update animation, get the socket trasnformation from the weapon mesh, trasnfer it to the bone space called shotgun socket (this is the socket I created under character mesh), store it as a variable and called it effector location 0

At the Hand IK module, hook up the effector location with this variable effector location 0

End result,

When holding a gun and not fire, it is ok as left hand is not required to move.

But when fire, the fire animation does play, but only arms part are moving, the left hand still stays at same locaiton relative to the weapon.

Spend days to solve this issue still no luck, any sugestion or another solution is highly recommended, thank you.