The Vulcan Cannon is basic weaponry of nearly every vessel in the Space Corps and thus present in every mission. The vulcan is an energy weapon with a high rate of fire, capable of shredding through most Bydo fairly quickly. The vulcan can only be fired directly ahead of the craft. R-craft are equipped with Wave Cannons for situations that the built-in vulcan cannot handle (which comes up fairly often). The Vulcan Cannon fires in conjunction with Force weapons, and many Forces will use their own vulcan cannon when disconnected from the warship. Charging a Wave Cannon temporarily disables the Vulcan Cannon until discharged, though Missiles will continue to fire.
Since the vulcan's ammunition is drawn from the warship's power plant (which is built to handle infinite Wave Cannon shots, a far more intensive weapon especially considering the Giga Wave Cannon), ammo for this weapon is infinite. However, commanders in R-Type Command/Tactics will find that Vulcans have an ammo max of 99, which is near enough to infinite for the scope of the game.
Compare the Bydo Shot, the ubiquitous Bydo equivalent. The vulcan has a faster rate of fire, but the Bydo Shot is slightly larger and can be fired from any angle.