Excalibur: the Dual-Shot, Four Ranged Cannon

Hello everyone! This is my first instructable and today I am going to teach you how to build my favorite cannon: Excalibur. You can shoot 2 blocks of TNT 4 different ranges in just the push of a button! So let's get started!

Step 1: Getting Started

First make a U-shape of light-green wool 6 blocks long and 3 wide, leaving a 1-block space at the back. Place redstone dust on top of each block to create a wire.

Step 2: The Elevation

Starting at the front, place 4 light-green wool blocks in the center of the U-shape but raised one block higher. This will eventually be the water bed. Now add 1 red and 1 light-green block to the back of the cannon as shown. Place a redstone torch on top of the red wool and redstone dust on top of the light-green wool.

Step 3: The Frame

Build an L-shape of red, white, light-gray, gray, and black wool, positioned a block higher than the red wool with the redstone torch attached to it. Place a ladder on the inside of the red wool at the top of the L-shape. Since ladders occupy an entire block, this will act as a rest point for the TNT projectiles and will stop the water from spilling out.

Step 4: The First Dispensers

Add a single stone slab to the end of the L-shape as shown. Aim for the top half of the red wool when placing the slab. Now add 4 dispensers opposite the longest side of the L-shape, facing in toward the water bed. These will dispense TNT into the cannon.

Step 5: The Redstone

Lay redstone dust along the stone slab and the dispensers (PC/Mac users use shift, or when flying space+shift. Console players, crouch while placing.) Place a red wool block above the redstone torch. Place 5 repeaters along the L-shape as shown, all facing toward the front of the cannon and set to 4 ticks. Using a water bucket, add a single water source block to the back of the water bed, so the water will flow forward.

Step 6: The Dual Shot Addon

Add 2 dispensers to the top of the wool block with the ladder attached, both facing in toward the water bed. Now add 2 stone slabs as shown, and place 2 red wool blocks on top of these slabs. This will leave you with a single block of air in front of the 2 projectile dispensers.

Step 7: Fill 'er Up!

Fill all 6 dispensers with TNT and add 4 range selector buttons along the side of the cannon. Pressing the button on the black will allow you to fire TNT the farthest, and the button on the white block will fire it the shortest distance. Have fun experimenting with range!