Lee's carbide factory die is a tool; if you need one, get it and use it correctly. You will find it to be great for the purpose it was intended for. The carbide FCD, like any other tool, if you need one it's great but those who assume it's supposed to work some kind of miracles in every instance are going to disappoint themselves. Our choices are to load for max accuracy or max reliability.

Manufactoring tolerances of bullets, cases dies and chambers can stack in ways that make things that do not fit. Many cast bullet shooters are (wrongly) convinced that lead bullets should be larger than their bore so they make some fat ammo. Cases are not made with the precision of a Swiss watch. Loading fat bullets in thick cases to firing them in tight chambers can get jammed; in a gunfight, that can be very inconvenient.

Lee's excellent FCD handgun crimper with its post seating carbide ring will make ammo that shoots well and will avoid jamming every time it's tried. But, it's just a tool, people who have fat chambers and make correct diameter cast bullets and load them in thin wall cases will never see any difference.