I own the special edition.

On AR-15 family guns when you reload you can smack the side of the receiver with your hand to jar the bolt loose and chamber the next round, which is what Kilmer did.
For the most part, cars will only give you concealment in a gunfight, especially if you're being shot at with high velocity rifle rounds. The only part that you can really count on to consistantly stop bullets is the engine block. That was shown pretty accurately. You see the bad guys' 5.56mm NATO rounds going right through most cars, and when Al Pacino is reloading while Val Kilmer is shooting at him, he's deliberately crouching behind the
front of a car so the engine block will shield him.