Shreq Airsoft talks about fine tuning your airsoft gun and explains why. Fine-tuning an airsoft rifle is less about magic and more about making sure your piston and BB are on the same page. The goal is to ensure the BB exits the barrel exactly when the piston hits the nozzle. If the piston slams home while the BB is still inside, the resulting vibration can cause the barrel to twitch, sending your shot off-target.