All you have to do is load up the bottle cartridge which can be any plastic bottle with your liquid of choice. Then screw it onto the Shot Gun and tug the slider to make all liquid break loose. It will shoot out liquid even further if you pull this as hard as you can.
Every pump will squirt out about 17 milliliters of liquid so it does measure out a drink perfectly. To make things even more interesting, wear the cut-out sunglasses that come with the gun. You, your glasses, your drinks and your Shot Gun will make a lasting impression. As you recover from the party, give younger ones a shot at it. They can choose whether its drinks they splash out with it or whether they will have one big, water shot-to-kill party.