For Minecraft on the PC, a GameFAQs message board topic titled "I present: The fully automated, self-reloading TNT cannon array.". Ahh my first Redstone device An Auto Reloading TNT cannon Press the button and get ready for explosion Or maybe launch yourself Download map now! The Minecraft Project, Auto-Reloading TNT Cannon, was posted by dom54g. Jan 10, · Quick Summary. To make a cannon in Minecraft, start by equipping 16 blocks, 11 redstone, 5 TNT blocks, 2 levers, 1 slab, and 1 bucket of water. Then, make 2 parallel rows of blocks that are 7 blocks long and separated by 1 space. Next, connect the ends of the rows with a block and place your last block on the top-left block%().