This is a TnT Cannon design I stumbled upon while I was TnT cannon testing for a pvp server. It surprisingly shot 150+ blocks away from the cannon. It uses 10 tnt per shot. I use 2 buttons for more design. You can use 1 lever and repeaters if you want to. 2 buttons just seems easier to control to me. Also, you will need to use a very long delay if you want the TnT to go as far as it is suppose to.

I've been trying to make a different version of this that shoots vertically, but I have no luck. If any of you TnT fanatics can design a cannon that is like this, but shoots vertically, please message me a design for it.

Anyway, enjoy the magnificent and powerful cannon!