Trasnforming Bone and Pose with Attached Weapon

I am trying to find out how to correct the weapon attached to the hand IK when transforming the spine. The gun is attached in the viewport and when I correct the spine the weapon stays where it was before without the spine transform. I was wondering how I can fix that. This is just a sprinting animation where I need the pose not to lean forward too much so I modify the spine a bit.