Strategically moving your cursor from top to bottom while the gun is firing can focus the shots into one mostly tight cluster. The main action needed when doing this is starting at the top of your screen when facing left, then quickly moving downward as the gun fires. Likewise with facing right, you start at the bottom & quickly move upward as the gun fires. This of course is best done with homing arrows but also works with bullets.
0.8: Reduced attack speed.
0.7.2: Now crafted at the Shrine of Legends.
0.7: Added a right click attack which fires arrows instead of bullets.