If you're shooting sabots that are tough enough to hold together out to forty yards and make a hole in the hide, they'll make holes in paper. Sabots normally fall off and hit the ground at 20 to 50 feet.
The bullet turned and came back out. Weird things can happen with lead core bullets. This was one of them.
I had the same thing happen to me in an open field with a ballistic tip bullet.. nothing there I thought.. but it grazed some broom sage and caused the bullet to come apart.
That wouldn't happen with a patched roundball or conical.