Cannon

A cannon uses gunpowder to propel heavy balls of cast iron through the air at destructive speeds. In a campaign without gunpowder, a cannon might be an arcane device built by clever gnomes or wizardly engineers.

A cannon is usually supported in a wooden frame with wheels. Before it can be fired, the cannon must be loaded and aimed. It takes one action to load the weapon, one action to aim it, and one action to fire it. Multiple creatures can work together to handle a Siege Weapon

Ammunition & Gunpowder: The Cannon uses a 24 lb Cannon Ball and 1/2 lb Gunpowder per shot.

Cannon Maneuvers:  Proficiency with Firearms in combination with 24h of studying of the cannon unlocks special maneuvers which enhance attacks made with this weapon. Each use of a maneuver must be declared before the attack roll is made. You can use only one maneuver per attack.

Loading. It takes one action to load the weapon 

Aiming. It takes one action to aim the weapon

Cannon Ball. 
Ranged Weapon Attack: +6 to hit, range 600/2400 ft., one target. Hit: 52 (8d10) bludgeoning damage.

Firearm Proficient Maneuvers:  

Cannon Attacks (Recharge 3-6). Instead of loading and aiming you can use the Recharge Die as Bonus Action at the beginning of your turn to ready the Cannon.

Grapeshot Blast.  
The cannoneer fires a shot loaded with 2lb of grapeshot pellets (e.g. Ball Bearings, small metall pieces,...) in a 20-foot cone in front of him. Every creature in that area must make a DC 15 Dexterity saving throw, taking 28 (8d6) piercing damage on a failed save, or half as much on a successful one.

Exploding Shot. 
The cannoneer fires a shot that is a fragile, red hot ball of metal. The cannoneer fires it up to 70 feet away. Each creature within 20 feet of the detonation must make a DC 16 Dexterity saving throw, taking 18 (5d6) piercing damage and 18 (5d6) fire damage on a failed save, and half as much on a successful one.

Chain Shot. 
Ranged Weapon Attack: +6 to hit, ranged 300/1200 ft., one target. Hit: 61 (8d12) bludgeoning damage. The target is Grappled (escape DC 15) if it is a Huge or smaller creature. Small or smaller creatures have advantage on Dexterity (Acrobatics) checks to escape the grapple.

Precise Chain Shot. 
Ranged Weapon Attack: +1 to hit, ranged 300/1200 ft., one target. Hit: 71 (8d12 + 10) bludgeoning damage. You take a -5 Penalty to aim for the mast of a ship or something flying in the air. If you hit the target is destroyed (mast) or knocked Prone (flying).