Maybe physics works differently on bullets and airsoft BBs, but it's also one thing to understand the other when shooting behind a vehicle. Tactical Rifleman shows the best shooting positions in doing so... "In this video Rob, from T1G, takes us through a demonstration of how bullets skip off of cars at different angles.

I'm talking especially about the hood and trunk, but it applies to all surfaces of sheet metal.

When a bullet hits the sheet metal at a low angle (say 10 degrees), it does not bounce and exit at the same angle (10 degrees) like when you are shooting a game of pool. Rather, the bullet pushes into the metal, creating a wave up front (like water in front of a ski). Now, once it gets built up, either the metal gives way (creating a hole where the bullet then enters the car), or the bullet deflects up and departs at a greater angle."

Read more here.