The Vulcan Cannon is the default weapon in many titles of the Raiden series. It is a standard vulcan cannon, a common element in many shoot 'em ups. First appearing in the original Raiden up to Raiden IV, the cannon has since appeared in a majority of the overall series' titles as well as all of the main series' titles. When the player loses a life in any of the main series' games, their primary weapon will always reset to the Vulcan Cannon.
The Vulcan Cannon takes on the appearance of small, orange, bullet-like rounds that fire from the nose of the player's controlled starfighter. Despite their small size, the Raiden Supersonic Attack Fighter and the Raiden mk-II are capable of unleashing an endless wave of bullets, which can be devastating amongst clustered enemies and very useful for finding hidden secrets.
Initially, the weapon will start as a simple two column line of bullets, one way that travel straightforward and deal minimal damage given against most enemies and bosses, but upon collecting red power-up, the spread and firepower of the bullets will increase, thus increasing the effectiveness of the weapon. Upon being fully upgraded, the Vulcan Cannon will unleash a total of 7 individual columns when fired, 1 straightforward line and two lines of 6 columns angled to fire to the left and right respectfully, allowing for most enemies to receive incoming damage taken from the say weapon.
From Raiden III to Raiden IV, it is upgraded from one way to three ways (as Fighting Thunder ME-02), the marked increased firepower of over one-way Vulcan Cannon from previous Raiden games.
While the wide spread of the bullets is the main strength of this weapon, the Vulcan Cannon, even when fully upgraded, cannot reach enemies within a gap between to either the left or the right of the main stream of cannon fire. As mentioned before, the damage output of the bullets individually is not very impressive, requiring several rounds of bullets to destroy even enemies with moderate durability. This negative feature however can be countered as the player continues to collect red beacons to help upgrade the weapon and increase the overall damage output. Additionally, the weapon deals more damage for every bullet that hits an enemy.
In Raiden III to Raiden IV, if the Vulcan Cannon is collected while using a different primary weapon, it will level out to the exact level of the previous used weapon (for example, if the player has the Ion Laser equipped and has collect only a single beacon upgrade, should they collect the Vulcan Cannon, it will be equipped as though it has been upgraded once as well.