For the most part I am happy with the Lee Undersize 9mm die with the Squirrel Daddy pins. But with my recent migration to the RL1100 there is greater consequence of a primer not getting clear of the pin, since the next station is swaging and it will smash the thing right up in there again, and then there is no primer pocket for the primer, and since you are seating while you are sizing there is no so much feel as with most other presses.
The other day it occurred to me that maybe there is no place for air to vent in while the primer is being pushed out (the collet is pretty tight around the pin)?
I thought I would pop a small hole in the die, way up higher than the sizing is happening, as an experiment. Just did about thirty rounds and the primers do seem to be hitting the catch bin with a little more velocity. This might be my imagination, but seems to have helped.
Just passing this along, wondering it makes sense to anyone else.