I think this will be useful for gun builders. Seeing the whole picture of what's going on will help.

This might not be %100 of what's going on but it is pretty close. Any mistakes seen will be gladly appreciated.

I will put a couple of hand drawings up trying to make sense of everything going on.

I'll add descriptions later on.

Point P is the point around which a gun can pivot. Somewhere in the wrist depending on how you hold the gun. The *W*'s are the weights of the gun and spear and the *By* is the buoyancy force. Bouyancy force is the weight of the water displaced minus the weight of the wood gun.

*b* is the band lenght and *d* is the distance from band hole to notch and *B* is a point on the notch.

Also the mass of the person is much greater than the mass of the gun and spear which I have asssumed makes point *P* stationary. That is, a force exerted by the gun cannot move the person due to their mass and surface area.