The carbide ring is the main issue. If you have a cylinder or chamber that is a bit oversized, and your sizing your bullets bigger than normal, it can and will size the bullets smaller as the case goes through.
I picked one up for my 45acp loads and found that the ring was simply too small and every time I pushed a round into it, no matter how it was adjusted, the brass would be squeezed down around the bullets resulting in them being swedged down at least .002" or so depending on which bullets I am using, and if I actually size them before loading.
This might be fine for some, and some might find no issue what so ever with theirs, but if you read enough reports on others having the identical issues when using cast, and the FCD, you can really only come to one conclusion.
Personally after I popped the ring out I have not had one single issue with it since. So if you REALLY want to try one out the worst case is you "might" have to pop out the carbide ring.
Mike / TX