I saw a 75mm shell bounce off a M16 once.
Perfect aim, fire, * kaboom *..
the shell flies, impact, and then.. it goes * boing * and the shell bounces vertically... on a M16.
Determined to prove this absurd behavior, I recoreded almost all of my GV sorties after that incident, and experienced same things quite a few times... however, it was then I found out the shell bouncing isn't recorded in films.
...
Damn!