To make it:
Use an expended cartridge. That means a bullet that has already been shot. Do not under any circumstances use live ammo.
Mount an empty shell in to a drill press. Make sure it is on it’s lowest RPM. Use a pipe cutter to cut off the primer end. File the back side flat.
For the pin part I got a pack of “pins and clutches” from the craft store; 10 for $3.00. Cut the pin out of the backing. Mount it into a drill press and file it down until it fits into the hole in the back of the shell.
Place a piece of solder into the shell. Heat it from the bottom so the solder seeps into the hole. While the solder is molten, place the pin in the hole. File away any excess solder.
To polish the completed pin use 1000 grit sand paper followed by polishing compound and a polishing wheel.