Updated with more info, at the bottom are the question marks I still don't know.
One thing I'd note to any lurking devs, the Artillery tree needs a lot of tweaks for the non crafting portions. I could maybe see someone quickly respec'ing mortar reload time in a pinch but generally you have npcs on cannons, swivels etc. This means that the reload time talents, the improved targeting speed talents, etc are all pretty much useless. It's not like the current base targetting speed is all that bad for any of them in particular either.
Would really like to see either something like an artillery perk that give a bit more (doesn't have to be much!) range, or gives a cooldown similar to that of the other trees at the bottom to make artillery more effective somehow.
Here's what I've figured out so far:
1) Mortar- By far the best weapon in the Artillery tree. Excellent (ridiculous on cliffs or stone towers!) range, does hardcore damage on ships, which they can outrange. Can swivel left and right. It does not have the vision problems other guns have where you can't see the target of the arc well. Only shoots the mortar shot. This is -the- base defense and harbor defense weapon against hostile ships.
This is also one of the more feasible current strategies for besieging someone, if you can find a spot not covered by their mortars, claim it and set up your own mortars to bust a hole in their base.
The only con is you can't put them on ships.
2) Medium/Regular ship's cannon. These are the cannons that go into gunports on a ship like a brigadine, the large cannons -do not- fit. They're effective if not that powerful at base level, but the power can be compensated by having a lot of them or by crafting better ones from blueprints (recommended). You can assign NPCs to each cannon and order them to fire at the podium or wheel. They can swivel left and right, and are going to be the main weapon against ships of the damned or pvp player ships. Don't seem all that effective against stone buildings.
Extra Ammo: Bar shot, it is an ANTI-SAIL shot, aim at the mast or Sails to do more damage... it is designed as a disabling shot. It is also a high end creature bola (!??!).
3) Large Cannons-Very limited but Powerful. To get them on ships you need to build a support structure, easiest technique is on a ceiling supported by 4 walls, with a sloped wall (ramp) going up to the cannon. The important thing here is they can't swivel, they can only shoot near or far, not left or right. The ship's navigator has to line up the enemy ship to be in sight of this. However they do a good deal more damage to enemy ships and have better range as the tradeoff. If you have a skilled navigator who can "Jiggle" the ship to line the shots up this is probably the one to use.
Important notes: First of all, the ceiling/walls/ramp setup and the cannon itself does NOT count as part of the ship and has to be repaired separately and has a longer cooldown before the repairs can be made. Also the actual ship deck under the ceiling/walls will still take damage (IE isn't shielded by the walls/ceiling/cannon 100%).
These can also be used to fair effectiveness against stone buildings if you can get them in range, and if so are the most cost efficient method (mortar shots and tnt barrels are expensive)
4) Swivel Gun- Great defensive tool for your ships and bases. Man them with NPCs, and use windows on ships, and set them up to shoot at your front door in bases (or from the side or into hallways, w/e). Instant death to most intruders with Grapeshot. It's also viable to set up a swivel on a fast ship and run alongside a ship to burn them with liquid fire, which does great amounts of damage. Recommend using a fast schooner for this against bigger boats.
Greek Fire talent=Liquid Fire=Basically the swivel gun becomes a flamethrower. Not instantly lethal but burns enemies with a fire dot. Very effective against ships as well.
Canister Shot=Shoots an explosive charge. Seems to do decent damage to wood, untested on stone or players.
Grapeshot=Shoots a conal aoe (very short range but strong, can one shot). Probably your best defense against boarders.
5) Puckle Gun- Decent elevation and might be the best "NPC Gun" for anti-player defense (aside from short range base/ship traps that use swivels). Does decent damage but not as much as a flintlock in a player's hands. One positive is that if surrounded by 3 walls on a foundation and looking out a doorway "wall", animals cannot attack the NPC manning it, they'll strike at the puckle gun without doing damage. Cannot be set up on ships.
6) Grenades-Does massive damage to mortars and cannons (much more than to regular stone structures). Does decently against players and tames.
7) TNT Barrels-Can be fired from large cannons (Short range but powerful). Can be laid down to explode with a timer. Immense damage to ships if placed correctly in water.
8 ) Oil Jar-Not strictly artillery tree but worth mentioning. Need flame arrows as well to use these, they're low budget but work very well if you want to glide or hook on to assault enemy ships. The best strategy if you can see the ship's captain is to oil jar+fire arrow at the ship's wheel. Otherwise doing the same at cannons is effective in stopping their attacks for a bit, and it does well against ship planks.
9) Ballista - Used for hunting whales. Decent against other things too but so cost inefficient as to be laughable, just hunt Moby Dick.
10) Catapult - Low budget but I struggle to find a use for this, the aiming, range and damage seem inferior to a cannon in every way.
Honorable mention to the ammo storage box that is also craftable from this tree. It functions as a "trough" for ammo that your cannons automatically consume from, IE put one down in the middle of your ship (below deck and in a sealed room!). Then place all your cannonballs, liquid fire, grapeshot, etc etc in it and they'll be consumed from every armament on board.
Still Unknown:
Spike Shot - it seems very weak? It's basically a cannon shot that sticks and does an explosion after a while, but I struggle to find any use for this?
Canister Shot - explosive round from the swivel, again I have a hard time seeing this do more than liquid flame against ships, or do more against players than grapeshot. It does seem to have a bit more range but...???
The problem isn't that the Chinese are good, it's that there's rampant cheating going on and 9/10 times it's the [][][] tribes. You can't fight back against duping, aimbotting and being shot inside of your enclosed base.
