If you can finish a wave of enemies before moving to the next point, your weapon will reload automatically, saving time. Do not waste time reloading during the fights unless you are actually out of ammo. Upgrades You must upgrade your weapons in order to be successful. Try to have more than the minimum required weapon power to pass the missions. Upgrading requires time. To be efficient, start one or two upgrades while trying two other missions. Play them until you are maximum, then begin to upgrade those weapons. Keep the weapons upgraded evenly for use in the main storyline.