I saw one of these pens several years ago and thought then I could make it, I just didn't know what to do with the pen mechanism. Then I came across a pen kit at Rockler Woodworking and then it was a little tinkering to make it happen.
Step 1: Materials
Rockler Pen Kit (www.rockler.com)
30-30 Shell Casing
5/16 inch brass tubing (from craft/hardware store)
Step 2: Pen Tip
Cut the back side off the bullet approximately 1/16 inch behind the line. I did this with a jewelers saw.
When the end is cut off, heat the bullet up and the lead will easily drain out.
Step 3: Assemble the Lower End
Because the brass tip is very soft, I turned down an insert out of brass, that would fit inside the bullet tip. When it fit, I put the three parts together (second photo) and soldered them.
With the lower half of the pen connected, now it is time to work on the top.
Step 4: Pen Top/Pocket Clip
I made the pen top out of a 30-30 shell casing and a 1/8 inch piece of brazing rod. Bend it free hand so that it fits on the lip of the casing, and then touches at the bottom. This will create a pinch point to keep the pen in your pocket.
I brazed this on, but you could also use solder or silver solder and it will be fairly solid.
I had to clean this on a wire wheel and then shine it on the buffer.
Step 5: Assemble
Once the lower and upper halves are together, it is time to assemble the rest of the pen.
The two brass tubes that come with the kit provide a friction fit so that the pen will extend. To get it all together, I superglued the brass tubes into the open ends of the halves.
Once this has set, then you can press fit the mechanism into the lower half. Adjust it so that the pen tip extends out the end when turned.
Now just slide the top half onto the pen, and you are done.