Dual Shot TNT Cannon

Materials Needed:

 * 21 Blocks (any kind)
 * 8 Repeaters
 * 7 Redstone Dust
 * 5 Dispensers
 * 1 Fence (any kind)
 * 1 Wooden Pressure Plate
 * 1 Sticky Piston
 * 1 Button
 * 1 Water Bucket
 * Lots of TNT!

Step 1
Place 5 blocks in 2 pillars, 1 3 blocks tall, the other 2 blocks tall; place a dispenser pointed toward the other pillar on the 2 block high pillar; place a fence in between the pillars; put a wooden pressure plate on top of the fence post.

Step 2
Put 4 blocks going out of the fence post to form the bed of the cannon; make sure this is pointed the opposite way that you want the cannon to shoot.

Step 3
Put 4 dispensers pointed toward the bed, opposite the first dispenser (make sure to hold shift when you place them, PC edition only); put 4 blocks opposite the dispensers.

Step 4
Place 7 blocks in a ring, leaving 1 block open, the one by the 4 dispensers.

Step 5
Place a sticky piston pointed upward in the gap of the ring; place a block on top of the piston.

Step 6
Place redstone dust on top of the dispensers (hold shift while doing this to put the restone on top of the dispensers, PC edition only)

Step 7
Make a clock circuit, with the repeaters set to 4 ticks, make sure they point out of the piston block.

Step 8
Put 4 repeaters heading toward the original dispenser, make sure they are set to 4 ticks

Step 9
Put a button on one of the 4 side dispensers; put water in the bed of the cannon; fill the dispensers with TNT!

You are ready to fire!