Easier way to proceed (and you might totally abandon the Hornady tool, as I did):
- Resize a fired case per your usual process.
- Use a hacksaw or Dremel tool to make two vertical cuts on the case neck, from mouth to shoulder.
- Resize the neck. You now have a case which will hold a bullet snugly but allow said bullet to be moved with relatively light pressure.
- Seat a bullet long in the split-neck case (you want the bullet correctly aligned).
- Push the assembled "cartridge" completely into the chamber, which will push the bullet into the lands before the bullet slides back in the split case.
- Taking care to protect the crown, insert a cleaning rod into the muzzle and carefully push the "cartridge" loose.
- Repeat steps 5-6 a few times, until you don't feel resistance to pushing the bullet out of the lands.
- Take your COAL / CBTO measurement.
I found that this procedure gives CBTO measurements to the lands that are much more consistent than the Hornady tool ever did.
My $.02.