Hint - Weapon Power-Ups
Weapons can be upgraded in a stage if you find a specific power-up.
Although you cannot carry the upgrade from one stage to another, it
will benefit your weapons within that stage.
Mission 1 - Weapon Upgrade
Parachute onto the western cliff and look for the upgrade adjacent
to the boxes, near the searchlight.
Mission 2 – Weapon Upgrade
Look for this upgrade on the counter of a small building at the
entrance of the courtyard.
Mission 6 – Weapon Upgrade
Parachute into the western tower (the one emitting green gas) and
look for the upgrade on the top floor.
Mission 10 – Weapon Upgrade
Inside the tunnel after the first 88, the upgrade can be found
behind a box at the end of the first corridor.