I recovered some 9mm bullets after the snow thawed and I can see an extra ring in the bullet that is from the case mouth.
I use the Lee FCD and don't have any problem with leading at all. I do notice that during load development I get primer intrusion into the firing pin channel well before reaching max loads. I realize with an inertia pin such intrusion is not necessarily excessive pressure but it is a nuissance when bits of metal shave off and clog the channel. I have trouble trying to mimic factory velocities and or POI. Factory loads will exhibit the same extrusion but mild enough that it doesn't shave off metal.
So, would a lighter crimp keep pressures down so that I could get a little more velocity before the primer intrusion sets in?