Buddy Holly wrote:Wstops half way.

by half way do you mean a rotation of 180 degrees?? if so, then buddy got you the answer.. since there is no key in the lock, the keyway is open on the bottom (and some cores have holes on the bottom so you can repin it easier.. either way, either the key pins are hitting the holes on the bottom, or the driver pins are hitting the bottom of the keyway.