Here is a great project for used brass bullet shells!

Step 1: Tools and Materials

Materials:

-Used bullet shell (doesn't really depend on the size)
-Scrap metal (preferable the same type as your shell)
-Small fake diamond

Tools

-Saw
-Hammer
-Drill
-Sand Paper
-Polish
-Solder and flux
-Torch
-Super glue

Step 2: Cutting the Shell

First Drill out or remove the primer, mine had already been done. Then saw off the primer end of the shell and sand it down till you have just the back end.

Step 3: Making the Ring

     I used a 50 cal. shell and cut it at about the middle. You can use sheet metal too, or just a piece of pipe, but I used a shell so the metals would be matching.
     If you are using a pipe cut a section that is a little wider than the primer end of the bullet shell. For me, the shell was to small to fit anyone so I used a vice to clamp down a solid round piece of metal and hammered the ring on it. This will eventually make the ring bigger until it reaches the size you want.
     Now you can start shaping the ring, I used a bench grinder at first, then moved to a file and finished with sand paper. Try to get a nice symmetrical shape and make sure you make it wide enough for the butt of the shell.

Step 4: Fitting the Ring Together

Now, sand or file the bullet shell butt so it fits nicely on the ring. This can be challenging but it will make it look really nice. It is okay if its not perfect just do your best.

Step 5: Soldering

I used a vice to hold the ring in place then soldered the primer end of the shell to the ring. Be sure that you center the primer end onto the ring.
You may have to do some touch up sanding around the joint.

Step 6: Set the Stone

To set the stone put some super glue into the hole and place the stone how you want it. Make sure that the stone is not tipped or weird looking when it sets.