Just took a course at Sig Academy over the weekend, Bullets and Vehicles, very informative (and a lot of fun). Highly recommend if you have the opportunity to take it.
The 1st half of the course was all about shooting from inside a car, either from the driver seat or passenger seat. Biggest concern is accessing your firearm due to seat belts and other "impingement's". Other concerns are the cramped surroundings and being able to position yourself and maneuver your firearm. Major thing to avoid is bringing the gun to a "low ready" position or aim/pass the gun in a barrel down direction because you will be aiming right at your legs, really bad things there that you don't want to accidentally hit, ie. femoral artery, femur, etc.
When shooting thru side windows or the rear window the glass is "safety glass" which shatters after the 1st shot and that 1st shot may be deflected when penetrating the glass.
To the front (thru the windshield), the concern is that the glass is laminated so it does not shatter and will affect the trajectory of each bullet (unless you put them all in the same hole), the bullet will rise after penetrating the glass the amount of rise is dependent on the angle of the glass, the more angled the glass the more the rise. Also, a FMJ bullet will start to separate after penetration of the glass so not only the bullet but also the fragments may hit your target.
(Part 2 will relate to 2nd half of the course - ballistics on and thru a vehicle)
A bullet will actually "skip" across the surface of the trunk or hood, take home point, if using a car for cover DON'T lean on the hood or trunk the bad guy doesn't need to even aim properly to hit you (Pics 1 and 2)
Penetration of doors: most rounds penetrated 1 door and a lot will penetrate 2 doors a good percentage of the time (9mm, 40, 44mag, 5.7, 357, 308, 223, 12ga slug, 338) (Pics 3 and 4 show door penetration)
Nothing penetrated the engine compartment and most did not penetrate the "B" pillar (Pic 5)
It was!!! Nice facility and great instructor, will be planning a trip up there again.
Also, got to shoot a "bean bag" shotgun round thru one of the side windows and a 40mm "nerf ball" on a side panel after one of the other guys shot one thru one of the other side windows.
Besides being serious fun (come on any day at the range is fun but getting to shoot up a car, that doesn't happen everyday) it really was very informative.......of the 8 students only 2 of us were civilians, I guess up and till a couple years ago Sig only taught LE and Mil and not civilian, happy they changed that