I once loved the Lee FCD. It fixed all my reloads that didn't chamber. Then, I stopped using the FCD after a commercial bullet caster named Dardas explained to me that the FCD was swaging the bullets with those cases that didn't chamber. Then, I did a test using PC 38-148 WC sized at 0.357" with 2.8gr BE with the only variable being the case. Seating depth at the crimp groove. All cases were 2nd firing range brass and the case lengths were the same. My best groups used Remington brass with thin walls. Winchester not as good, I use Federal, Speer, brass vs nickel.. The worse was PMC. The walls were thick, didn't chamber, and I had to use the FCD. I even shot a mix of brass and the group size was a combination of the other groups using different headstamps. My conclusion is to find what brass shoots best with your load because the wall thickness effects neck tension and a more consistent accuracy. Stay with one headstamp. Either test them all or measure the ID to your bullet OD and the measurement should be .002"-.003" difference as mentioned in an earlier post. Anything less and your bullet will fall through. As for crimp, I'd I remove my case flare with my crimp die. If I crimp, I start at the non-flare position and make test loads of various crimps created by turning my crimp die down by 1/4, 1/2.. turns and then compare my groups.