The bullet does not automatically start to rotate when it exits a human body. A bullet tumbles in response to interacting with a solid object such as bone that deflects its trajectory. It does not deflect appreciably when it transitions from one medium to another such as flesh to air or water to air, etc. It certainly doesn't rotate appreciably within a couple of feet of exiting the body.
Otherwise, a bullet follows a parabolic path like anything else under gravity. The mussel velocity defines the parabolic arc of a projectile, which is insignificant over a hundred feet and has nothing to do with a tumbling bullet.
Where did I address bullet tumble in my post? I'm questioning your use of a laser beam which of course is not affected by wind, air temperature, air density or gravity as is a bullet in flight. At that distance it might only be a barely noticeable drop (as I understand it, nevertheless one is talking fractions here. My research is talking 200-300 yards downrange and beyond.
I might be getting the wrong idea about what you say you are proving.
Re tumble, I understand Carcano rifling grabs that ammo near the front rather than the back, thereby providing a very stable bullet in flight.
