Well I don't have the means whereof to fire my shotguns while suspended in space, in fact I don't believe this can be accomplished within the confines of gravity. While true this info is of little practical value to me. As I do fire my guns from the shoulder then the ppoint of contact at the butt is below the bore axis, which does indeed cause the end of the bbls to rise upon firing as they are pivoting off that contact point. The flip we are speaking of comes about by the muzzle not rising quite as fast (In proportion to its length) as the breech, or it "Bends" a bit.
This could all be seen clearly if one could simply shoulder a gun, mark the bore axis point on a target & then without moving fire the gun. You could then compare the center of the pattern with the where the bore was actually pointing. Marking directly above this center point by the amount of drop of the charge over that range would show where the bore was pointing at the tim the shot left the muzzle. "IF" you could then without changing anything else liminate the "Flip" & fired another shot you would get a point of impact slight above the first firing.
Remember that "Flip" does not necessarily mean the gun is going to shoot Below where its bore was pointing, it just won't hit as high as if it didn't exist.
