I know that the OP - bemore2156 is trying to make us a BETTER cartridge holder which is great and wish him sucess. He has a lot of good ideas to hold cartridges.
Always good to have someone trying to make shooting/hunting equipment for us.
For many years we have been using "Soft Case Cartridge Wallets" when in the field. You can put in you pack, outside your pack, on your belt, and in your pockets. Has elastic to hold the cartridge, Velcro, snaps, & clips to secure to just about anything.
We carry 204, 223, 243, 260, 270WSM, 325WSM in different size wallets.