Minecraft wiki entry for TNT_cannons, associated text: It will launch several blocks of TNT at your target, however it is expensive and does not have a very long range, but with a big cannon, you can shred a large amount of land with each shot. Occasionally the redstone will be blasted off if you have a large cannon, so it is good to keep some redstone on hand. Good for the defense of a village (blast mobs with a row of cannons when they come too close!). Best for creative mode due to the large amount of TNT needed for each shot.