Oh, God. This is a mess. So every time you hit an enemy you increase your fire rate at the trade off of low damage and poor shot accuracy. If a bullet hits a wall it resets the fire rate. You also gain ridiculous recoil as firing speed increases. The firing rate caps at about 0.05s/bullet to keep things a bit balanced. Special places down a bomb that does a small but powerful explosion.
This took some inspiration from two Splatoon weapons: The Dark Tetra Dualies and the H3-Nozzlenose.