Due to limitations with vanilla Minetest Game, TNT cannons cannot be constructed.
This mod addresses this by adding a new node called a cannonball, which can be launched by cannons.
To launch a cannonball, place it near TNT and ignite the TNT.
I have found that the setup shown in the screenshot is ideal for launching the cannonball in a certain direction.
When the cannonball hits something with enough force, it will cause an explosion.
Create 8 cannonballs by using the crafting recipe which is eight steel blocks surrounding gunpowder.
Ideally this mod should be used in competitive multiplayer or pvp, but it can also be used in singleplayer.