EPIC MACHINE GUN CANNON!
Step 1: Materials
2 powered rail, 1 detector rail, 1 minecart, 1 despenser, 2 redstone torches, and a LOT of arrows.
Step 2: How to Make It
If you are dumb and can't figure out how to make it by the pictures, then TOO BAD!
Step 3: Bigger One
This one was a bit bigger, but I wanted the other one.
You can make the track longer for a bigger delay.