The correct way to use the Lock Ring Eliminators and Breech Lock Bushings is as follows:
The half moon cut out on the Lock Ring Eliminator/Breech Lock Bushing is meant as a stopping point to adjust your die in the Bushing, especially to release the Lock Ring when you need to turn the die in and out of the Bushing. To lock the Bushing, you need to depress the Pin and spin the Bushing clockwise to lock and engage it into place.
There are times when the Bushing will be a tight fit when the half moon cut out is aligned with the Lock Pin.
Video on how to install a Breech Lock Bushing:
Video on how to remove a Breech Lock Bushing:
Video on how to install the Lock Ring Eliminator: