Honady has the words spire point with cannelure what does it do for the bullet .
Thanks
Bill

Substitute 'crimping groove' for cannelure and you have it...

bill,
this is the groove (or grooves) AROUND the bullet, that is designed, with the brass cut to spec, that will allow you to crimp the brass on the bullet, for spec OAL.

of all the reloading "things" it's probably the most ignored

jeffe

The cannelure (crimpimg groove( is used on some rounds to lock the bullet in place so that it will not move under shock from the action. Example the M-16 requires a crimped bullet so that the rapid action does not lossen one of the bullets causing a mis loading of a round. Also The 30/30 and other lever actions with tubes mags use a crimp to make sure the bullets stay in place as they hit on each other. Some fire arms require this to operate properly.