Minecraft wiki entry for Getting_to_the_worldborder, associated text: When he was ready to go to the world border, he constructed the machine near a chunk border, set his difficulty to peaceful and put his render distance to the lowest, threw an ender pearl and started the machine. The reason for this is because the machine is constructed near a chunk border and the machine started producing multiple copies of TNT, the TNT gets pushed outside the chunk border and is considered by the game as "frozen". Due to this, the TNT isn't exploding, the same with the ender pearl, as it was outside the chunk border and hit a cobweb which was one of the materials of the machine.