Two things you need to grasp in a firefight.
It's gonna be LOUD, REAL LOUD!!! We wear ear plugs and ear muffs at the range, but you're never gonna have any ear protection in a real life situation. Are you ready for that? Disorentation will need to be overcome quickly. Practice without ear protection a few times to see how it feels.
Learn to reload during the firefight. It's easy at the range. I bet not in a stressfull envoirnment. My Glock only holds 6 rounds, but 2 extra clips might be needed if you miss with a few attempts. Remember, conditions will be less than ideal.