Quick update. Inside the Attach to hand method, even if you use offset and adjust your gun, the ALS has 3 animations, gun ready, gun ready to calm, and calm (not the exact animation names btw). And the ik bone to which, the gun is attached moves in each animation, thus, if your skeleton was not perfectly adjusted to the skeleton, the gun would warp from one point to another and basically fly around the hand or something.
The method I found that works best in all three animations is to attach the gun to “index_01_r” instead of the default “VB RHS_ik_hand_gun”, to which it is default attached. This will ensure that your gun always remains with the index finger of the character regardless of animations. This is done inside the same AttachToHand method
Also, if you’re planning to use the left hand too, then change that ik bone to the respective left hand index finger bone too.
Just wanted to update this in case it helps somebody 