Digital Vernier

I say digital, because they are ubiquitous and cheap. If you don't already have any, buy two and keep one spare. You must have this to

  • ensure that your case is within the allowable trim length
  • ensure your loaded rounds are to within the maximum permissable AOL for the cartridge and bullet you are reloading
  • A manual vernier is just as accurate, if you already have one use it.