How to Make a "Ballistic" Pen

This tutorial will show you how to take a gel pen and transform it into a pen launcher, with a similar form to the Ballistic Knife found in Black Ops.  This can launch anything, from an ink cartridge to a wad of paper.

Tools of the Trade:
Scissors
An eGel Avery pen (link found here)
(A Pilot G-2 is a passable substitute, but the spring can't be as strong)
A large spring

Now for the fun part!

Step 1: Disassemble Pen
Unscrew the front part of the pen and remove the ink cartridge inside.

 Next, take the cartridge and poke out the plunger housed in the back of the pen.

You should have these two parts separated now.

Now take the spring out of the front part of the pen by hitting it on the floor. (yeah, seems strange, but it's the only way to take out the spring)

Step 2: Reassemble the pen
Now you have to put the parts back, but in a different order.  But before you do that, you should first get your large spring.

The spring should be powerful, but not so strong as to not stay in the "armed" position.
Now rearrange the parts.

Put the parts back together in this order: plunger, spring, lock.

Step 3: Modifying the tip
Before anything can be launched out of the pen, we first need to either chop off the tip of the pen (Pros: Launches larger objects. Cons: Takes a while to cut) or simply make it larger (Pros: Much faster, easier. Cons: Limited to ONLY disposable pen ink cartridges)
So I will split this step up into 2 sections.

Step 3a: Cutting off the tip
This is much harder to do, but it is worth the larger variety of ammo you can use.
First take off the grip.

This pen is complete!  To arm it, just push the ink cartridge down the barrel until you hear a click.  Press the plunger at the end to launch the cartridge.  Or you can remove the cartridge and drop something down the barrel, such as a wad of paper, a toothpick, or a different ink cartridge.

Step 3b: This is the simpler version which only requires you to grind down the sides of the pen tip.
Insert scissors and turn until you can fit a disposable pen ink cartridge inside it.

This pen is also complete!  The only difference is that you are limited to firing the ink cartridge of a disposable pen.