To keep relevant info handy I've copied this from the Beginner's Guide:
-Action1 gives no stat bonuses.
-Action2 gives a slight boost to the fire rate and increases recoil.
-Action3 increases the fire rate, reduces recoil and adds tech.
-Action4 reduces the fire rate, greatly increases recoil and increases damage.
-Action5 (preferred) greatly increases the fire rate and increases damage. __________________