Spinning bullet, why?
no, no shatter. Perhaps if I describe how they are made it would become clearer. Take ordinary concentric projectile, it has center of mass in geometric center of rotation. Drill out core slightly off the center and replace it with either heavier of lighter metal. Result will be that projectile will have new center of mass around which it will be rotating. Geometric shape will 'wobble' around it while in flight. Thats basically excentric (eccentric?) bullet. Nothing else. Normally, its considered bad bullet, but in this case its intentional and controlled eccentricity. New center of mass is supposed to be well aligned with flight path.
If I understand it right, then whenever such bullet brushes anything, it touches it with either front or rear edge and due to force from rotation goes precessing. After that its center of mass stops being aligned with flight path, its tip follows spiral around the flight path while gyro effects try to stabilize it again. Because of wobbling, force acted on it during brush is heavily sideways with little longitudal forces. Due to very high rpm, the sideways force can be pretty high, causing trajectory change. I don't know, maybe air drag is major factor here, thinking of why tree leaves might have such impact on it. Anyway, its not an ordinary ricochet.
When entering tissue, every density change is causing trajectory change, due to higher drag sharper changes, and bullet is messing around in body like mincer quite alot before it stops, causing very nasty damage beyond any hope of survival. Thats what I've heard.
I really don't know, but I'd be interested if someone could explain what behaviour is expected from heavily eccentric bullet.