This simple but powerful manual dispenser-based cannon only has 1 power source - the lever. Flip it to "powered" state to release the charge. Flip it once more to release the shell.
Pros: Very simple and powerful.
Cons: Expensive dispensers, slightly tricky to efficiently use.
The technical name for it is 216.0MM3 dispenser:
- 2 (overlapping) rows of TNT
- 1 shell
- 6 charge TNT total, 2 rows of 3
- .0 - no condensation.
- M - manual cannon.
- M3 - slab mounting block.
- Special:
- dispenser - dispenser-based cannon.
Also, you can add a comparator and a hopper for manual setup. But you'll want to compensate the extra tick of the comparator by adding a repeater on the other side. The darker blocks are 2 high:
The measure of hopper A is subtracted from 15. The output will be 0-3, depending on the amount of items in hopper A.
Hopper A must contain at most 3 full stacks (or non-stackable items) and 60 items for the adjustable row to work on full strength. Each additional 23rd item will turn off a dispenser sequentially, beginning from the front. See also Redstone_Comparator#Measure_block_state for the exact values.