It's best to lay them out on a piece of colored hard board, or heavy cardboard. Find a large picture frame first, that will hold the number of cartridges you want to display. When you lay them all out, take a Sharpie, or fine tip pen, and put a dot on either side of each case. This will give you a mark to drill a small hole for a retaining wire. After drilling a hole for each cartridge, get some small copper wire, and push it through the holes, securing the cartridge to the board by twisting the wire together on the back.
Rainbow or circular patterns look better than straight rows. If you need more room, a small half circle inside of a larger half circle will get them all in. Try to type up labels to glue on beside each cartridge, to identify the caliber. This is similar to what the ammo makers did with their bullet boards in the past. If you want to get really creative, you could get a picture of a big game anaimal, and have it blown up as a background for your display board.
Good luck!
