Hello, its ObscureClockwork
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This is a very small TnT Cannon, but uses up to 5 TnT to send a block pretty far away for its size.
it works on the new TnT dispensing, as well as up and down dispensers
It is rather powerful because all 5 charges are right behind the projectile.

Please diamond if you like the variations/cannon design

The basic design takes

• 3 blocks
  
• 6 dispensers
  
• 1 bucket of water
  
• one fence
  
• one trapdoor
  
• one button
  
• one lever
  

Pros

• Cheap
  
• Adjustable power (through filling dispensers)
  
• fast(ish) reloading (due to dispensers)
  
• accurate
  
• powerful
  
• adjustable mounting (fence, or upright trapdoor, or replace fence with block)
  
  

Cons

• Basic design is not automated
  
• low tune-ability (all charges in one place)
  
• high vertical velocity (you may want to bury this a bit lower)
  

Whats included:

• Basic design
  
• Rapid fire (with adjustable clock [1/2/3/4 ticks]
  
• automated
  
• 2nd rapid fire (10 shots per second)