Bob Palmer at Hornady, in an e-mailed reply to George's enquiry:
CCI makes the cases for all the .17 HMR ammo and loads it for the different companies. When they make the cases they draw the case out to a .22mag case that has a straight wall. Then the priming compound is put in the rim of the case. The case is spun to put the primer evenly in the rim.
After the priming is complete the case mouth is reduced to the .17 calibre to hold the bullet. The reduction process, however, puts stress on the neck of the case. They obviously cannot anneal the neck of the case to relieve the stress becau