I built these cannons originally for my youtube channel: zeNUKEify. They all use redstone. Mods can be attached to increase the power of the cannons dramatically. I made these cannons on a techic mod pack called explosive craft classic. So far, ive completed the Striker Cannon, a small cannon capable of firing explosives all the way up to tntx5. The cannon is however, unstable with larger explosives. Those explosives have a radius so large, the cannon could be damaged.

              Of course, the Striker Cannon is only the "level one" of my cannons, I attempted to make a larger cannon, which I named the "Voltron Cannon". The voltron cannon quickly ignites all the bombs used to launch the explosive. Then it uses pistons to push the bombs all right under the explosive to launch it. The pistons move at a 4tick difference. Sadly, this means that the pistons move so fast that the second ones fires before the first one retracts. This causes the bombs to glitch into the pistons sometimes, blowing up the cannon. I am currentally trying to solve the issue!

STRIKER CANNON VIDEO: https://www.youtube.com/watch?v=qfEB6f-Ul8A
VOLTRON CANNON VIDEO: https://www.youtube.com/watch?v=aIBilgiAMK0
   
MOD PACK: www.technicpack.net/modpack/details/explosives-craft.5723