Watch the Digital Ammo Counters on your weapons and the bottom right corner of your HUD and make sure that the ammo in your weapon is not running out
When it gets low, or when you have a moment to breath, you should reload your weapon. Reloading is an action that takes a few moments in which you are not shooting, so don't do it if you are under attack and still have ammo left. Wait for better opportunity or for when you have really run out of ammo.
Reloading a weapon will fill the magazine up to its maximum Magazine Size
