I think we also have to keep in mind that it really depends on where around the circumference of the twig the bullet impacts. It's a difference of mere millimeters in POI with the brush, but can really change the outcome. If the bullet hits the tree or twig dead center, it will likely expand and carry on in a straight line. If the bullet glances off the side of the twig or tree, it will likely tumble and change direction. That is VERY hard to control, even for testing, because we're talking literally just a millimeter or two off to one side and the entire outcome can change.
