I named this the "1.3 Cannon" because of the lack of name that i could come up with and because Minecraft 1.3 is coming out soon.

This cannon uses some of the feathers that was added with the new minecraft its pretty useful because and taking full advantage of it. But what this cannon uses the most is the bukket in the dispenser giving the cannon a longer range and the water source problem solve. so in case you forget to put that water source will putting some TNT in it, it will blow up your cannon and lose all your hard work (Especially when its really complicated and you need to focus really carefully) and this solve it. But this cannon can only be use in the newest snapshot. Link will be provided if needed. Snapshot

Firing Distance- 32 1/2 blocks
TNT Rounds- 2 shot in one and 9 blocks distance
Firing Range Option- None
Lag Chance- 5%
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If there is any problem with this design please inform me for I could fix it and change it in anyway possible or have an idea for a future model. Enjoy ^_^