You are the Weapons Officer. That's right, you're entrusted with the big guns – a MAC Cannon that fires devastating torpedoes, a phase cannon bank that can be upgraded to rival any warship, and the dreaded Power Beam, which depending on how Engineering is being run may be middling or may cut through suns. Assuming the other Bridge Officers aren't absent and needed, you should be able to enjoy the most thrilling tactical ship-to-ship warfare available!
Bare minimum requirements: Know how ship targeting works, know how to fire the weapons. Communicate with the Munitions Officer about what rounds to load into the MAC.
As a Weapons Officer, your duty is to defend your ship from enemy ships. This is done with the Tactical Console and the NARV's onboard anti-ship battery of weapons of mass destruction. The gunnery console is a little more straightforward than the helm console, but it pays to have munitions tech experience. Knowing the rough ammo capacity of different weapons can be useful, but the names themselves are fairly informative. Hit the Space key to switch between weapons. Being on this console will also give you a readout on the remaining ammo (in percentages) of the ship's weapons, including those you can't fire from this console, as well as the ship's armor and structural integrity.
Your weapons include:
Torpedoes: Click in a direction after locking onto a target to fire a Torpedo. Torpedoes deal a significant amount of damage with a short travel time that may require a small amount of leading. Additionally, nuclear warheads can be loaded to deal a massive amount of damage but are difficult to acquire. Torpedo tubes also do not possess much ammo capacity, being limited to only a few torpedo tubes with a long loading time. Torpedoes do however have a homing effect, making for very good long-ranged weapons.
Naval Artillery Cannons: To shoot the Artillery Cannons simply click where you want it to hit. While this seems easy to do at the first glance, the artillery cannon requires more than just a single click to work. Before you can fire it needs to be loaded with gunpowder, as the amount of powder used affects the speed of the bullet. This means that you'll have to communicate with the munitions staff (radio hotkey: .w) to ensure the optimal bullet trajectory. This means that if the gun doesn't have much powder loaded the bullet will move very slowly, and you must aim your shot in where you expect the enemy to be instead of where they currently are.
Automated Missile System (AMS): The missiles are an easy to use automatic defense and offense weapon. Their targeting systems are controlled by the Munitions Technicians and can choose between multiple firing modes. If they are set to Countermeasure mode they will automatically aim at incoming torpedoes and missiles, while Anti-Ship mode gives you (and the fighter pilots) direct control over where the missiles are heading. To set a target for the missile system simply hold CTRL and click with the left mouse button or press “Target” on the Tac console's UI. Fighter pilots can also do this for ships that are outside your view range to make it targets further away.
Point Defense Cannon (PDC): Point Defense Cannons are as the name implies: defensive utilities. They fire a large volume of bullets in a short amount of time. This makes it great for taking out incoming torpedoes or fighters, but ineffective against larger opponents. The Helm console can also fire the PDC, but unlike the helmsman, your PDC is fully automatic. This makes you, the gunner, better suited to laying down defensive fire.
Phase Cannons: Your ship also has two banks of phase cannons that you can use to fire at close to medium range targets; while your starting allotment of two phase cannons is unimpressive, a full bank of sixteen cannons will shred ship armor and quickly neutralize shields. Phase Cannons use energy to fire and as such their 'ammo' count is based on the current charge in their banks.
You will also have a readout of the Gauss and the Superliminal BSA, however these are not under your control. Gauss cannons are controlled directly by Munitions Technicians (or other crew, if applicable) while the BSA is controlled by the helm officer (see above).
If this still isn't enough firepower for you, your R&D department can help build more and stronger weapons, and you can salvage parts to upgrade your weapons as well.
The onboard anti-ship battery has a maximum effective range of about that of a planet; beyond this point, most ships will be able to evade incoming fire, although stations, satellites, and other stationary debris can still be hit. If you're at a nav beacon and you target a ship that's not at the nav beacon, you're wasting ammunition. Wasting ammunition's a surefire way to piss off both the Captain and the Munitions Officer.
Also note that targeting different areas of the enemy ship will yield different results if you go to salvage: For example, targeting the hull will destroy the cargo holds and thus reduce the available loot you can scrap from the wreckage, while targeting the weapons will reduce the chance of salvaging a new phase cannon.
At the top of the screen, you can observe a vaguely hexagonal elongated shape with three layers; this represents your ship's hull, armor, and shields (if activated). The hull and armor begin green and slowly turn red as the ship takes damage. The shields start bright blue and fade with damage. While the shields are up, they act as a physical barrier, easily blocking small objects from entering or exiting the ship, meaning you'll want to turn off the shields if the Supermatter Shard is delaminating. This also obstructs teleportation and transportation - shuttlecraft, fightercraft, and salvage teams will not be able to bring scrap in or head out to salvage while the shields are up.
Important: Whenever a ship is destroyed and its position navigated to, it will spawn its wreckage in front of the ship, which can be a risk if there is other wreckage not yet attended to.
When looking at enemy vessels, be sure to note their location. If they are not at the same planet/nav beacon you are, then you are out of range and your shots will do nothing. Also, when firing at enemy ships, you can select various subsystems to target. Damaging and destroying these hinder the enemy ships. Destroying the shields allows more of your shots to do damage, destroying the engines reduces their evasion, shooting the bridge will also reduce their evasion, and shooting at the hull will destroy the enemies' cargo holds. Where you target determines the state of the salvageable wreck. Use this strategically to salvage certain items for your ship!
Although the Head of Personnel is technically your immediate supervisor, 99% of the time you'll be answering directly to Command. It's important to keep the Captain informed and up-to-date on threat assessments, and to prioritize ship defense over other activities when actively under attack. If no member of Command is on the Bridge, the Comm Officer should be calling them out of their happy relaxation time should you be shooting.
While the Weapons Officer generally orders the Munitions Officer around in terms of ammo-loading, you should remember that they are both on the same level in the chain of command - neither one outranks the other. For example, a Munitions Officer is not obliged to allow a Weapons Officer into the Munitions Bay if asked to do so by the Weapons Officer.
When a boarding party is on site, and/or the Marines are actively working on taking a position, you get the added responsibility of providing ship-to-target fire support. In this, you will be listening to the Overwatch Officer, who will call out coordinates for bombardment. Be advised that your shots will target these coordinates, which may be danger close if the caller isn't careful…
You will note that you have access to the Supply Requisition Terminal on the bridge; in the event that your ship's Munitions budget is bulging, you can place orders for additional ship weaponry, weapon reloads, shield reinforcement units, etc. If you choose to use this for personal orders, however, the Quartermaster, the Head of Personnel, and Command are all in their rights to tell you where to stick your requests.
Traitor time! Finally, you have an excuse to use that big cannon of yours to blast away at passing spaceships! Unfortunately, you're bound to get caught very quickly, making Traitor Weapon Officers incredibly unlikely picks (as their activities generally quickly end the round, unless they're patient or smart.)