One thing I know for sure. In my XD40, which really doesnt really like SWC's anyway.
Loading Missouri 170 SWC, I have to seat them at 1.110 to get them to fit the chanmber. No matter what I do, they would not feed , until I ran them through the FCD. I dont know why, but the ones that have been run through the FCD function 100% . I would prefer not to use the FCD on lead, but in this case I do.