Various loaded cartridges
Drill press or hand drill (I used a drill press)
Twine, string or other necklace material (I used hemp)
Start by selecting how you want the bullets to be arranged and mark the points where you have to drill for the string to pass though. One the hole is drilled though, carefully dump out the gunpowder and set aside. I used a larger bit and chamfered the edges of the holes to make them burr-free. Thread the string through and add the clasps.
In the end, I used a square knot and then a half hitch on the clasps to prevent fraying. Add a drop of super glue as you see fit.
No need to make this seem more complicated than it is,... you could easily add beads, charms, pistol rounds or whatever else you want.