During the course of the game, you can augment the stats on your Buster Gun with Buster Parts. If you switch Buster Parts just after firing some shots from it (while the shots are still on-screen), you can change the Attack power from the shots. For example, if you fired a volley of shots with a +3 Energy/Rapid stat (thus, six very fast shots), and swap to a Buster configuration with +7 Attack, you will find that, despite the stats changing, the volley of shots is just as numerous and fast as before, but they're actually much stronger now as a result.