I think the commentary in this thread covers the topic very well, and the link with all the pics explaining these relationships among the case, bullet, dies, and chamber is excellent. This is a fairly complex set of mechanical relationships, probably as much as the ordinary reloader will ever encounter.
1. The empty cartridge case must be suitable for reloading, in most cases this means it can't be too long....not much of an issue with a low pressure round like .45 ACP.
2. All the dies must be set correctly, not just the crimp die. This has been well covered in previous posts. The OP states he is using the FCD, so that means a 4-die set, which removes some of the complexity, but I will re-emphasize that the seat die must still be set correctly.
3. Too much flare on the case is a problem that seems to crop up in every forum I visit. Apply just enough flare so that the bullet can sit on the case after flaring without falling off. If the case starts looking like the bell on a trumpet, you have gone too far, and will end up ruining your cases.
Good luck!