Howitizer was the best name i could fit to this instructable, its simple, not very accurate, but it may be good for bombardment, with a lot of them.
Step 1: Parts
These are what you will need
Add more orange/whites if your ram(last step) wiggles, and comes loose
Step 2: Supports
Make 2 of the deign shown.Step 3 will show both of these
Step 3: Supports 2
This is pretty much the main step , almost everything connects to these parts!
Step 4: Connecting-Connection
Add the Yellow rod to the current model.
Step 5: Ram
This is the most important step, do it very carefully.
Connect the Blue to the Orange, and add it to the Support, as shown,
Add the rubberband to the end of the ram, to the front support
Add a orange connector to the the yellow rod, next to the front support
Step 6: Launching
Pull back the ram, add a white rod to the front support(make sure its in far enough)
and let go of the ram!